Chapter – I

Evaluation of multivoltine and bivoltine breeds/race of the silkworm, Bombyx mori for

quantitative traits employing inbreeding coefficient, narrow sense heritability and

evaluation index

Introduction

Introduction The domesticated silkworm, Bombyx mori L., is a lepidopteran insect known

for the production of silk “queen of natural fibres” and extensive genetic studies have

been carried out utilizing this insect (Tazima, 1978). By virtue of the applied

importance in the production of highly durable and attractive silk fibre, it qualifies

itself to occupy a high pedestal in the textile industry (Raje Urs, 1988). In many

countries sericulture is an important source of revenue and generated self-employment

enormously. Sericulture originated from China and spread mainly in temperate

regions of the world, where exclusively the bivoltine silkworms are reared. However,

in the course of time, it spread to more than fifty countries in four continents (Wu &

Lin, 1994).

The mulberry silkworm B.mori due to its immense economic value has wide

distribution with well-defined geographical races (Gamo & Ohtsuka, 1980) and Asia is

the major producer of silk in the world. India, being second world leader in sericulture is

gifted with salubrious tropical climatic condition (Nirmal Kumar & Qadri, 2010). Hence

the silkworm rearing and mulberry cultivation is practiced throughout the year. India

largest producer and consumer of silk, second in global silk production by producing

23,060 MT of silk (CSB Annual report, 2011-12) has the unique distinction of producing

all four major types of silk namely mulberry, tasar, eri and muga. Among these mulberry

silk contributes bulk production (18472 MT of silk).

In India, indigenous polyvoltine breeds like Pure Mysore, C.nichi in south

India, Chotapolu, Borapolu, Nistari, Nistid, Nismo, Itan and Ichatin in West Bengal,

Sarupat and Moria in the north east, Kashmiri race in Jammu and Kashmir were

reared and multiplied at field level for the production of silk (Ghosh,1949) and many

of them being reared even today. Bivoltine rearing was restricted only to maintenance

and multiplication of exotic races such as J112, J122, C108, CPP1, CC1 and CA2 up to

1950. As a result there is a rich collection of multivoltine and bivoltine silkworm

races / breeds in several germplasm stations of our country. The first trial of rearing of

silkworm hybrids was attempted in 1923 in Karnataka by crossing the multivoltine

Pure Mysore race with exotic bivoltine Chinese/Japanese races and it was

commercially exploited in 1925.

1

A critical analysis of Indian sericulture reveals that majority of the silk in

India is contributed by multi x bi hybrids. (Himanthraj et al., 1996; Roy et al., 1997;

Datta et al.,2001; Dandin et al., 2003 and Ishita Roy 2011), where females of

multivoltine breeds/races of silkworms are crossed to males of bivoltine breeds/races.

It is important that in south Indian states the practice of utilizing multivoltine Pure

Mysore race as one of the female parent for the preparation of hybrid layings

dominated the sericulture industry.

Perusal of literature has clearly indicated that many systematic approaches

were made to improve Pure Mysore race through conventional breeding methods. The

pioneer attempt in this direction was made by Narasimhanna & Gururajan (1965),

Sidhu (1967), Sidhu et al., (1968). During 1970s, some prominent multivoltine breeds

like Kollegal Jawan, Kolar Gold, Hosa Mysore, Tamil Nadu white, A4E, MBDIV &

V, D14b, Mysore Princess were popularized. From 1980s, several research

programmes were oriented to evolve multivoltine breeds such as MY1, RD1, P2D1 and

PM (SL) in CSR&TI, Mysore and Berhampore and during 1990’s, MH1 and KHPM

(SL) breeds were popularized from KSSR&DI. From 2000 onwards few polyvoltines

like BL43, BL67, ND7, NP1 and APM series by APSSR&DI were used as one of the

female parent in the production of crossbreed layings for commercial exploitation.

Similarly, the Department of Sericulture, University of Mysore has evolved some

multivoltine breeds like MU1, MU11 and MU303 for commercial exploitation

(Subramanya & Sreerama Reddy, 1982; Vasudev et al., 1994).

During 1955-60 bivoltine breeding was initiated in India by Harada, by

isolating Kalimpong-A breed. Some more bivoltine breeds popular at that time were

KPGB, S21, HS6 (SL) and Sanish18. In 1970s, some high yielding bivoltine breeds

namely NB7, NB18, NB4D2 were evolved, popularized and used for a long time as

male parents in the preparation of crossbreed layings. At the same time PLF, BL1,

SF17, SS4A, SS15A and KY1 breeds were also isolated. Similarly, during 1980s the

bivoltine breeds evolved are CC1, CA2, YS3, SF19, JD6, SP2 and SKUAST series.

During 1990s, several research programmes were undertaken under World Bank

aided project and bivoltine sericulture development project by Indo-Japanese

collaboration, for the evolution of productive bivoltine breeds (Krishnaswami, 1983;

Datta & Pershad, 1988 and Basavaraja et al, 1995). As a result from 2000 onwards

2

numerous productive CSR breeds from CSR&TI, Mysore, KSO1 and NP series from

KSSR&DI, Pam101 and Pam111 from CSR&TI, Pampore, APS series by APSSR&DI,

thermo tolerant breeds like CSR18 and CSR19, (Datta et al., 2001), AHT, BHT, FHT,

GHT (Suresh Kumar et al.,2002), sex limited breeds like Nistari (SL), PM (SL), CSR8

and CSR2 (SL) CSR18 and CSR19 were developed (Datta et al., 2000b; Basavaraja et

al.,2004). Later on breeds like ATR series, SR2, SR5, B63, B65, CSR46, CSR47, CSR48,

CSR50 CSR51 breeds were evolved (Maribashetty & Aftab Ahamed, 2002; Siddiqui et

al.,2003; Suresh Kumar et al.,2004; Kalpana et al., 2005 and Dandin et al., 2006). At

the same time University of Mysore evolved some hardy bivoltine breeds like MG408

and MU854 (Ramesh et al., 1996). Thus, the silkworm breeders in India through the

application of the knowledge of silkworm breeding and genetics successfully evolved

multivoltine and bivoltine breeds suitable to different agro climatic regions of our

country. The expression of the genotype of the breeds/ race is best judged when

appropriate biometrical procedures are adopted. Further, biometrical analysis plays

major role in germplasm maintenance, in selecting the parents for hybridization

programme to enhance the selection gain. It will also help in determining the selection

intensity needed at different stages of hybridization programme. Biometrical analysis

of inheritance of quantitative traits and interaction of different characters help in

identifying potential multi x bi hybrids. Hence, analysis of genetic parameters of the

evolved breeds in different seasons through biometrical genetics is very necessary for

hybridization programme. Among several biometrical procedures that are developed

in animal breeding programme, three popular procedures namely inbreeding

coefficient, narrow sense heritability and multiple trait evaluation index are of

paramount importance in identifying the races/breeds for hybridization programmes.

In sericulture practicing countries several pure races belonging to different

voltinistic groups are maintained in germplasm centers by selection and inbreeding to

maintain the original traits through generations. Silkworm gene banks assume

paramount importance as the reservoirs of biodiversity and source of alleles that can

be easily retrieved for genetic enhancement of popular breeds (Jingade et al., 2010).

Inbreeding produces negative effects such as homozygosity in selected populations.

These homozygous races are important source of breeding for hybridization

experiments. One of the measures of inbreeding is the traditional inbreeding

coefficient which corresponds to half of the relation between parents. Reduction in

3

fitness due to inbreeding is known as inbreeding depression and the probability of

occurrence of two identical alleles in the same individual by descent is known as

inbreeding coefficient. Understanding the effects of inbreeding for various traits can

be a very crucial point in the management of different populations of silkworms for

hybridization programme in germplasm centers. Thus, studies on inbreeding and

inbreeding coefficient will play an important role in race maintenance programme in

the germplasm stations.

The concept of heritability played an important role in silkworm hybridization

experiments since 1930’s. Lush (1943) defined heritability as the proportion of

phenotypic variance among individual in a population that is due to heritable genetic

effects. This is termed as “Narrow sense heritability” and designated as “h2”. Gamo

(1976) opined that heritability whether broad sense or narrow sense is useful to

silkworm breeders to estimate the important quantitative parameters in B.mori

populations.

Heritability of a trait is the property of a particular population at a particular

time in a particular range of environment. Narrow sense heritability is defined as the

ratio of additive genetic variance to total phenotypic variance (Kalpana, 2005).

Heritability is one of the most useful parameters in animal breeding and it is important

to know the size of the heritability when planning a breeding programme as well as

when predicting the response to selection or individuals breeding values (Murthy,

2007, Talebi & Subramanya, 2009; Shiva Kumar Bakkappa, 2012). Narrow sense

heritability is exclusively used by silkworm breeders not only to preserve germplasm

stocks but also to set objects of selection and design hybridization programmes and

prediction of expected response from artificial selection programmes. The choice of

characters to be selected for improvement in the breeding programme is always

dependent on the genetic variability of economically important quantitative traits. The

genetic variability includes genotypic coefficient of variation (GCV %), phenotypic

coefficient of variation (PCV %), environmental coefficient of variation (ECV %),

heritability percentage (narrow sense or broad sense) and genetic gain (GA %) of the

traits (Mousseau & Roff, 1987).

4

The important economic characters in silkworm are governed by the

cumulative effect of polygenes. Superiority for one or more character may not reflect

the overall merit of the breed/hybrid (Vidyunmala et al., 1998). To increase the

genetic importance of multiple traits simultaneously, selection index should be

devised imperatively. Selection based on multiple traits is useful in judging the

superiority of silkworms impartially and to evaluate desirable silkworm hybrids

(Narayanaswamy et al., 2002). Multiple trait evaluation index method is one such

method that increases the precision of selection of breed among an array of breeds by

a common index by giving due weightage to all the yield component traits.

In order to judge the superiority of the hybrids impartially a common index could

be used. One of the popular methods to understand the superiority of the hybrids is

evaluation index method (Mano et al., 1994 and Ramesh Babu et al., 2002). The

evaluation index may be defined as aggregate unit of the component traits that determine

the silk yield. This method is developed by taking advantage of the variation index value

method which is being used in the Japanese education system to determine students’

merit (Mano et al., 1994). The traits involved in the goals of breeding and predicting their

joint response to selection on all or any subset of character is of paramount importance

(Umashankara, 2004). Such an attempt was also made on silkworm by several breeders

(Nirmal Kumar, 1995; Naseema Begum et al., 2000; Ramesh Babu et al., 2002; Nazia

Choudhary & Ravindra Singh, 2006; Rao et al., 2006; Lakshmi & Chandrashekharaiah,

2007; Rayar, 2007; Nirupama & Ravindra Singh, 2007; Nirupama et al., 2008; Ramesha

et al., 2008 and Talebi & Subramanya, 2009).

Realizing the importance of the application of popular biometrical procedures

namely, inbreeding coefficient, narrow sense heritability and multiple trait evaluation

index and their great practical significance, a detailed investigation was undertaken in

this chapter to analyze the differential expression of the selected quantitative traits of

four multivoltine (MU1, MU11, MU303 & Pure Mysore) and four bivoltine (MG408,

MU854, CSR2 & NB4D2) breeds/race of silkworm, during pre-monsoon, monsoon and

post-monsoon seasons.

5

Materials & Methods

Materials and Methods Three multivoltine breeds MU1, MU11, MU303 were selected along with Pure

Mysore race and two bivoltine breeds of Mysore University namely MG408 and MU854

were selected along with NB4D2 and CSR2 as bivoltine parents to evaluate the

performance in three seasons of the year. The characteristic features of this

breeds/race are described in Table 1.The larval and cocoon photographs are shown in

Plates 1-8. They were drawn from the Germplasm Bank of the Department of Studies

in Sericulture Science, Manasagangotri, University of Mysore, Mysore. The disease

free layings were incubated and exposed to light on the expected date of hatching. I-

III instars were reared at 27-28ºC with 85-90% relative humidity and the late age

larvae (IV & V instars) at 24-26ºC with 70-80% humidity. At III instar, 1st day, the

base number is fixed for each breed/race by retaining 300 larvae. Each breed/race was

maintained in three replications by feeding suitable quality mulberry leaves harvested

from the irrigated mulberry garden of the Department of Studies in Sericulture

Science, Manasagangotri, Mysore. The rearing was conducted in three seasons by

following standard rearing methods (Yokoyama, 1963; Tazima, 1978 and

Krishnaswami 1978, 1986a&b). Depending on the temperature, humidity and rainfall

conditions, the twelve months of a year have been divided into three seasons, namely,

pre-monsoon, monsoon and post-monsoon. Pre-monsoon season starts from March till

June and is characterized by low humidity with high temperature and scanty rainfall at

the end of June. Monsoon season lies between July and October identified by high

humidity, moderate temperature with medium to heavy rains. Post- monsoon season

commences in November and ends in February with average humidity, low

temperature and no rainfall except few showers at the end of February.

During the rearing, the performance of all the breeds/race were analyzed by

assessing the thirteen quantitative traits namely fecundity, hatching percentage,

weight of single fifth instar larva (g), larval duration (h), yield/10,000 larvae brushed

by number, yield/10,000 larvae brushed by weight (kg), cocoon weight (g), shell

weight (g), shell ratio (%), pupation rate (%), filament length (m), denier (d) and

renditta (kg) following the standard procedures. A brief description of the quantitative

traits evaluated are given below.

6

Fecundity (No.): This character represents the total number of eggs laid by a healthy female moth. The fecundity was calculated by taking the number of eggs in each breed laid by a single female moth. Hatching Percentage: This character denotes the number of larvae hatched from the disease free laying. The hatching percentage is arrived at, after deducting the unhatched, unfertilized and dead eggs from the total number of eggs laid by a moth. Weight of single V instar larva (g): This trait reflects the healthiness and robustness of the larva. It is the measure of randomly selected larva weighed one day before spinning. Larval duration (h): This character is the measure of time taken from hatching till the commencement of spinning. The mean larval duration is derived by calculating the larval feeding and moulting periods in hours from I instar to V instar. Yield/10,000 larvae brushed by number: This character denotes the survival rate of the larvae that spins cocoons. The unit of 10,000 newly hatched larvae is taken as a standard unit. Yield/10,000 larvae brushed by weight (kg): This is the total quantity of cocoons in kilograms obtained for a standard unit of 10,000 newly hatched larvae. Cocoon weight (g): This is the average weight of a cocoon in grams derived by calculating the weight of a random sample of 25 male and 25 female cocoons. Shell weight (g): This trait represents the total quantity of silk in a cocoon. It is the average individual shell weight in grams of 25 male and 25 female cocoons selected for assessment of “cocoon weight”. Shell ratio (%): It is the ratio between the shell weight and the cocoon weight. It is calculated in percentage from a random sample of 25 cocoons. Shell weight

Shell ratio (%) = -------------------- x 100 Cocoon weight

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Pupation rate (%): Pupation rate percentage was calculated for each replicate on the

basis of the total number of live cocoons harvested.

Number of live pupae recovered Pupation rate (%) = ---------------------------------------------------- x 100 Number of larvae retained after third moult

Filament length (m): It is the length of the silk filament in meters reeled from a

single cocoon. The mean value of the filament length is obtained by reeling ten

cocoons.

Denier (d): It is a measure of the thickness or size of the silk filament in a cocoon ,

represented as ‘d’ and calculated by using the following formula,

Weight of the reeled silk Denier (d) = -------------------------------- x 9000 Length of the reeled silk

Where, 9000 is the length of the fibre in meters used as standard, represented in

gram units.

Renditta: It is the measure of production of one kg raw silk from good cocoons and

calculated as follows:

Weight of the cocoons Renditta = -------------------------------- Weight of the reeled silk

The data pertaining to the seasonal performance of seven breeds and Pure

Mysore race with respect to thirteen quantitative traits of economic importance were

statistically analysed for three seasons and expressed as mean ± SE. The mean values

were compared by using Duncan’s Multiple Range Tests (DMRT) and statistical

analysis were carried out for ANOVA following the method of Snedecor and Cochran

(1967) using SPSS 17.0 (2008). Analysis of Variance was applied to study the overall

differences among the genotypes. The following three biometrical procedures were

employed to analyze the pooled data of three seasons.

a) Inbreeding coefficient (Falconer, 1989; Subramanya & Stephen Bishop, 2009)

b) Narrow sense heritability (Falconer, 1989; Singh & Choudhary, 1979)

c) Multiple trait evaluation index (Mano, et al., 1993, 1994)

8

The Analysis of Variance was calculated by employing the following

statistical model:

Yij = µ + ri+ sj+eij

Where,

Yij = effect of ith race in the jth season

µ = constant effect

ri = effect of ith race

sj = interaction effect of ith race and jth season

eij = random component effect

a) Inbreeding coefficient (∆F)

In order to estimate the level of inbreeding and to investigate the occurrence of

inbreeding depression through inbreeding coefficient in selected inbred populations

seven selected quantitative traits namely, weight of single fifth instar larva (g), larval

duration (h), cocoon weight (g), shell weight (g), shell ratio (%), pupation rate (%)

and filament length (m) were selected. The results were computed for the above traits

according to the statistical model developed by Subramanya and Stephen Bishop

(2009) for estimating the inbreeding coefficient (∆F) through REML (Residual

Maximum Likelihood) method based on the equation described by Falconer (1989).

The single trait linear equation was applied as detailed below:

Rate of inbreeding per generation - Ft= ∆F + (1-∆F) Ft-1

Where,

Ft= inbreeding at generation t

Ft-1= inbreeding at generation t-1

For repeated full- sib mating: ∆F = 0.191/generation (Falconer and Mackay, 2009)

Based on the above equation, the data was subjected to general mixed model

analysis using Genstat 9 (2008) and a fixed model computation was performed by

including quantitative trait as one variate and fixed model as a covariate which

includes the interaction between races, replicates and generation square.

b) Narrow sense heritability (h2)

Among three replicates of three hundred larvae twenty five female and twenty

five male larvae were randomly picked during fifth instar, a day before spinning from

9

each replicate. The larval weight was recorded individually and left on mountages

separately for spinning and the cocoons were harvested. The data assessed for seven

selected quantitative traits were analyzed for mean, genotypic coefficient variability

percentage (GCV %), phenotypic coefficient variability percentage (PCV %), narrow-

sense heritability percentage (h2%) and genetic advance (GA at 5% level) following

the procedures of Falconer (1989) and Singh & Choudhury (1979) as detailed below.

Narrow sense heritability is calculated with the following equation

VA VA VA h2 = ------------- = ------------------ = ---------------------

VP VG +VE VD+VI+VE

where, h2 = narrow sense heritability

VA = additive variance

VP = phenotypic variance

VG = genetic variance

VE = environmental variance

VD = dominance variance

VI = epistatic interaction

PV Phenotypic coefficient of variance (PCV) = ------------------- x 100 Overall mean GV Genotypic coefficient of variance (GCV) = ------------------- x 100 Overall mean Heritability x PV Genetic advance (GA) = --------------------------- x k, Where k is constant (2.06) Overall mean

10

PV and GV can be estimated as follows

Treatment mean sum of squares Phenotypic variance (PV) = ---------------------------------------- Number of replications Treatment mean sum of squares – error mean sum of square Genotypic variance (GV) = ------------------------------------------------------------------ Number of replication

C) Evaluation index (EI)

The evaluation index is defined as aggregate unit of the component traits that

determines the silk yield. The pooled data was analyzed statistically during three

seasons for thirteen quantitative traits by adopting the multiple trait evaluation index

(EI) method as described by Mano et al. (1993, 1994).

A - B Evaluation index (EI) = (------------ x 10) + 50 C

Where,

A = Value obtained for a particular trait of a particular breed/race

B = Mean value of a particular trait of all the breeds/races

C = Standard deviation of a particular trait of all the breeds/races

10 = Standard unit

50 = Fixed value

For the three traits such as larval duration, denier and renditta the following

formula of Mano et al., (1993) modified by Subramanya and Talebi (2009) was

adopted since lower values are preferred by breeders.

B - A Evaluation index (EI) = (------------ x 10) + 50 C

The index obtained as described above was estimated for each of the trait

analyzed. Further, the indices obtained for all the traits were combined to get a single

value, the average of which is evaluation index value.

11

Plate

Plate

Plate

Plate 7:

e 1: V instar la

e 3: V instar la

e 5: V instar la

V instar larva

arvae of MU1

arvae of MU11

rvae of MU303

e of Pure Myso

12

breed

breed

breed

ore race 

Plate

Plate 4

Plate 6

Plate 8: C

2: Cocoons of

4: Cocoons of M

6: Cocoons of M

MU1 breed 

MU11 breed 

MU303 breed 

Cocoons of Purre Mysore racee 

Plat

Plate

Plate

Plate

te 9: V instar la

11: V instar la

13: V instar la

e 15: V instar la

arvae of MG40

arvae of MU854

arvae of CSR2

arvae of NB4D

13

8 breed 

4 breed

breed 

D2 breed 

Plate 1

Plate 12

Plate 1

Plate 1

10: Cocoons of

2: Cocoons of M 

4: Cocoons of  

f MG408 breed 

6: Cocoons of  

MU854 breed 

CSR2 breed 

NB4D2 breed 

Results

Results The data pertaining to the rearing performance of eight breeds/race for thirteen

quantitative traits during pre-monsoon, monsoon and post-monsoon season was

analyzed for mean, overall mean, standard error and CD at 5% values are presented in

Tables 2-9. The overall mean values for each trait are depicted in Figures 1-13.

Table-2 incorporates the results of the rearing data of the three evolved

multivoltine breeds and Pure Mysore race for thirteen quantitative traits during pre-

monsoon season. Perusal of the data explains that MU11 breed exhibited highest

fecundity of 514±13.22, whereas a lowest of 417±12.24 by Pure Mysore race.

Similarly, hatching percentage is highest in MU1 breed (98.77±5.71%), whereas larval

weight is highest (2.74 ±0.30 g) in MU1 and lowest (2.18±0.27 g) in PM race. On the

other hand, prolonged larval duration (629±14.49 h) was noticed in PM compared to

shortest (510±13.27 h) in MU1 breed. PM expressed highest yield by number of 9710

±62.58 and lowest by MU303 (9554 ±59.29). MU11 breed recorded a highest mean

value of 11.44 ±1.91 kg for yield by weight and PM revealed a lowest of 9.72 ±1.71

kg. A careful scrutiny of the data clearly demonstrated higher values of 1.215 ±0.577

g (cocoon weight), 0.189±0.003 g (shell weight) 15.55±2.22 (shell ratio (%)) and

535±13.45 m (filament length) by MU11 breed. Highest pupation rate percentage was

observed in PM (95±5.64). Further, the lowest mean values for denier (2.02±0.81) and

renditta (10.71±1.82 kg) were registered by PM and MU11 breed. Significant

differences were observed in PM for the traits yield by number, pupation rate and

denier compared to evolved lines (P<0.05).

The data pertaining to the rearing performance of the four multivoltines

analyzed for thirteen economic characters during monsoon season is tabulated in

Table-3. The values in the table reveal highest number of eggs laid by MU11 breed

(530 ±13.50) and lowest in PM (449 ±12.42). Regarding hatching percentage MU303

breed exhibited highest of 98.65 ±5.65. It is evident from the table that MU11 breed

scored first for the traits larval weight (3.02 ±0.31g), yield by weight (12.61 ± 2.01

kg), cocoon weight (1.315 ± 0.586 g), shell weight (0.217 ± 0.009 g), shell ratio (%)

(16.50 ± 2.31). MU11 revealed higher values for filament length (552± 13.60 m). The

longest larval duration (646±14.77 h) was expressed by the traditional Pure Mysore,

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whereas shortest duration of 535±13.41 h was observed in the larvae of MU1 breed.

Pure Mysore race excelled in its performance by exhibiting highest yield by number

(9774 ± 58.90), pupation rate (96 ± 5.65 %) and lowest denier (2.01 ± 0.80). The

highest and lowest mean values for the trait renditta is observed in PM and MU11

breed respectively. The evolved breeds expressed uniform trend for pupation rate

percentage and renditta. Significant variations were exhibited between MU1, MU11,

MU303 breeds and PM race for majority of the traits (P<0.05).

Table-4 presents the results of the rearing data computed for thirteen

quantitative traits of four multivoltines MU1, MU11, MU303 and Pure Mysore during

post-monsoon season. In Pure Mysore race the fecundity is 440 ± 12.24 which is the

lowest and a highest value of 526 ±13.23 was observed in MU303. In regard to

hatching percentage a uniform trend is noticed among all the multivoltines for the

expression of this trait. Highest larval weight of 2.84±0.30 g was noticed in MU1

compared to a minimum of 2.39 ±0.27 g in PM race. Total larval period prolonged for

656 ± 17.89 h in PM but in MU303 it is reduced to 536 ±13.64 h. The lowest

(9566±57.14) and highest (9674±56.87) values were observed for the trait yield by

number in MU303 and PM. Except PM, the other three evolved breeds exhibited

uniform results for the character yield by weight. MU11 breed ranked top by scoring

higher values for the traits cocoon weight (1.291 ± 0.574 g), shell weight

(0.208±0.006 g), shell ratio (%) (16.11 ± 2.25). MU1, MU11 and PM race recorded

highest pupation rate (%) of 95±5.64. The three evolved multivoltine breeds

evidenced uniform performance for the traits pupation rate, filament length and

renditta, thereby exhibiting insignificant differences (P>0.05). Significant differences

were observed in PM race for the traits yield by number and pupation rate compared

to evolved lines (P<0.05).

The mean rearing performance for thirteen economic traits of the four multivoltine breeds/race (means of three seasons) is given in Table-5 and depicted in Figure 1-13. Out of thirteen quantitative traits analyzed, the data clearly reveals the superior performance of MU11 breed by recording highest mean values for seven quantitative traits namely fecundity (520.00±14.57), larval weight (2.83±0.21 g), yield by weight (12.01±1.38 kg), cocoon weight (1.274±0.408 g), shell weight (0.204±0.003 g), shell ratio (%) (16.01±1.62) and filament length (542.33±9.99 m)

15

followed by MU1 and MU303. MU303 breed showed maximum value for the trait hatching percentage (98.59±4.00) while MU1 expressed lowest larval duration of 528.33±10.04 h. MU303 evidenced intermediary values for most of the characters observed. Though lowest values were noticed for most of the traits in PM race compared to evolved breeds, it occupied the first place for the traits pupation rate percentage (95.33±4.00), yield by number (9719.33±42.85) and exhibited lowest denier of 2.01±0.57. The trait renditta expressed uniform results in all the three evolved multivoltine breeds but it recorded a lowest value of 10.41±1.29 kg in MU11, Significant variations were recorded between Pure Mysore race and three evolved breeds (P<0.05). Further, the insignificant differences were expressed for the traits denier and renditta (P>0.05).

Table-6 embodies the data analyzed for thirteen selected quantitative traits of bivoltine breeds MG408, MU854, CSR2 and NB4D2 pertaining to the mean values, standard error, overall mean and CD @ 1% in pre-monsoon season. The data connotes highest fecundity in CSR2 (546±13.16) and lowest (525±13.01) in NB4D2 breed. Evolved bivoltine breeds MG408, MU854 and NB4D2 recorded higher hatching percentage when compared to the lowest value (93.68±5.64) in CSR2. The trait fifth instar larval weight evidenced maximum (4.62±0.40 g) and minimum (4.21±0.37 g) mean values in the CSR2 and NB4D2 respectively. On the other hand shorter larval duration (536±13.41 h) was recorded for MG408 breed compared to prolonged larval duration (565±13.77 h) in CSR2 breed. The two University breeds expressed consistent performance for the trait yield by weight compared to CSR2 and NB4D2. The economic traits expressed highest mean values for cocoon weight (1.901±0.577g), shell weight (0.385±0.009 g), shell ratio (%) (20.25±2.57) and filament length (998±18.60 m) by CSR2 breed than other three breeds. For the trait pupation rate percentage the three bivoltines MG408, MU854 and NB4D2 recorded 92±5.58, 92±5.52 and 92±5.54 respectively, thereby indicating uniformity for this trait (P>0.05) while the lowest value for this trait was shown by CSR2 breed (89±5.55%). It is interesting to note that denier indicated uniform results in all the breeds observed. Highest mean value of (9.16±1.73 kg) for renditta is registered by NB4D2 breed compared to a lowest value of 7.56±1.52 kg by CSR2 breed. Significant differences were observed for the trait larval weight, larval duration, yield by number, cocoon weight, shell weight, shell ratio (%) and pupation rate (%) (P<0.05) and insignificant variations were found for the trait denier between PM and evolved breeds (P>0.05).

16

The mean values along with standard error analyzed for thirteen quantitative

traits of the four bivoltine breeds during monsoon season are shown in Table-7. The

scrutiny of the data clearly explains that highest number of eggs were laid by the

breed CSR2 (565±13.48) against lowest number of eggs (550±14.03) by NB4D2 breed.

Though hatching percentage is superior in MG408 breed (97.10±5.71), the other three

breeds exhibited comparable data (P>0.05).The trait larval weight evidenced

significant maximum mean value of 5.20±0.41 g in CSR2 breed compared to MG408

(4.65±0.30 g), MU854 (4.57±0.30 g) and NB4D2 (4.03±0.39 g) breeds (P<0.05). For

the trait larval duration, CSR2 breed recorded the longest duration (568±13.80 h),

whereas shorter larval duration was recorded by NB4D2 breed (550±13.61 h). Yield

by number is significantly lower (P>0.05) in CSR2 breed (9481±60.23). For the trait

yield by weight, CSR2 recorded 18.66±2.48 kg, MG408 recorded 18.47±2.45 kg,

MU854 17.61±2.38 kg and NB4D2 breed revealed 17.52±2.38 kg. which are significant

(P<0.05). The economic traits cocoon weight, shell weight, shell ratio (%) and

filament length recorded highest mean values of 2.155±0.576 g, 0.457±0.013 g,

21.20±2.65 and 1061±18.67 m for CSR2 breed. Except CSR2 breed, MG408, MU854

and NB4D2 breeds demonstrated uniform expression for the character pupation rate

percentage. All the four breeds recorded consistent values for the trait denier. The

highest (8.32±1.63 kg) and lowest (7.13±1.31 kg) renditta was revealed for the breeds

NB4D2 and CSR2.

The analysis of the rearing performance during post-monsoon season of the

four bivoltine breeds for thirteen quantitative traits is shown in Table-8. It is clear

from the data that the highest (546±13.57) and lowest (540±13.51) fecundity was

expressed by the breeds MG408 and MU854 respectively. The hatching percentage is

maximum in MU854 breed (97.91±5.81), MG408 (96.65±5.65) and minimum in CSR2

breed (93.54±5.53).The CSR2 breed exhibited highest values of 5.06±0.41g for larval

weight, 594±14.27 h for larval duration, 17.80±2.38 kg for yield by weight,

2.00±0.574 g for cocoon weight, 0.396±0.006 g for shell weight, 20.55±2.58 for shell

ratio (%) and 999±18.54 m for filament length. The yield by number trait evidenced

the highest value of 9592±58.10 in MG408 breed and a lowest of 9301±59.76 in CSR2

breed. The highest pupation rate percentage was recorded by MG408, MU854 and

NB4D2 breeds compared to CSR2 breed (91±5.52). Significant differences were

recorded for pupation rate percentage (P<0.05), whereas non-significant differences

were noticed for denier (P>0.05) between them.

17

Table-9 explains the data related to the mean rearing performance of four

bivoltine breeds (Mean of three seasons) computed for thirteen quantitative traits and

the same is presented in Figure 1-13. The analysis of the data clearly shows that the

fecundity trait recorded higher values of 551.66±11.63 and 546.33±11.05 by CSR2

and MG408 breeds respectively compared to MU854 and NB4D2 breeds. Though the

highest hatching percentage of 96.82±4.03 and 96 ±3.99 is evidenced by the two

evolved breeds of Mysore University; MG408 and MU854 the lowest value of

94.30±4.00 was noticed in CSR2. The mean value is highest for the six traits namely

larval weight (4.96±0.30 g), yield by weight (17.66±1.71 kg), cocoon weight

(2.016±0.540 g), shell weight (0.412±0.003 g), shell ratio (%) (20.43±1.85) and

filament length (1019±17.195 m) in CSR2 breed. The shorter larval duration of

(549.16±10.09 h) was shown by NB4D2 breed. Yield by number exhibited highest

value in MG408 breed (9615.83±49.26). Significant differences were noticed for

pupation rate percentage (P<0.05) between CSR2 breed and the other three breeds.

The variations show insignificant results for the trait denier (P<0.05).The highest and

lowest values of renditta were expressed by NB4D2 and CSR2 breeds respectively.

The statistical analysis of the data of four multivoltines and four bivoltines for

inbreeding coefficient (∆F) along with mean values for seven quantitative traits and

statistical significance during six consecutive rearings are tabulated in Tables 10 and

11 and illustrated in figures 14-20.

The statistical analysis of the data for seven quantitative traits of three evolved

multivoltine breeds along with traditional Pure Mysore race for mean values and

effect of inbreeding coefficient during three seasons are recorded in Table-10. The

results clearly demonstrate that highest ∆F value was exhibited for the traits larval

duration and fifth instar larval weight among all the multivoltines. For the trait fifth

instar larval weight MU303 breed recorded maximum ∆F values of 0.38±0.90 followed

by MU1 (0.38±0.83), PM (0.33±0.92) and MU11 (0.33±0.93). Thus, the evolved

breeds and Pure Mysore race expressed uniform performance with non-significant

(P>0.05) effects of inbreeding depression for the trait larval weight. A maximum ∆F

value of 0.43±10.60 and 0.43±5.35 were expressed by MU11 breed and PM race for

larval duration, followed by lowest values of 0.41±10.78 in MU303 and 0.41±11.11 in

MU1. The larval duration trait clearly evidenced positive non-significant ∆F values

18

(P>0.05) without any inbreeding effects by their higher standard error values. Cocoon

weight revealed highest ∆F value of (0.042±0.047) in MU1 breed followed by MU303

(0.041±0.051) and the lowest value of (0.023±0.057) by Pure Mysore race compared

to an intermediary value of 0.031±0.055 in MU11 breed. ∆F values for shell weight

registered highest in MU1 breed (0.013±0.014) followed by MU11 (0.011±0.012),

MU303 (0.007±0.009) and the lowest value of 0.002±0.005 by the Pure Mysore race.

MU303 and MU11 expressed maximum ∆F values of 0.05±0.50 and 0.04±0.43 for shell

ratio (%), whereas similar ∆F values were noticed in MU1 and Pure Mysore race

(0.03±0.40) and MU11 (0.03±0.39) respectively. The high standard error values

assessed over mean values for cocoon weight, shell weight and shell ratio (%)

confirmed the insignificant (P>0.05) ∆F values thereby indicating the absence of

inbreeding depression. It is interesting to note that the trait pupation rate percentage

showed lowest ∆F value in Pure Mysore race (0.004±0.68) and highest in MU303

breed (0.08±1.31) and intermediary ∆F values for MU1 (0.06±1.08) and MU11

(0.06±1.15) breeds. On the other hand Pure Mysore race exhibited a highest ∆F value

of 0.17±8.59 for filament length followed by 0.16± 9.26 (MU303), 0.13±10.35 (MU11).

A lowest ∆F value of 0.12±10.11 in MU1 breed and inbreeding depression is non-

significant (P>0.05) for these traits. The overall picture that emerges from the results

in Table-10 and Figures 14-20, clearly demonstrates that the traditional Pure Mysore

race exhibited lowest ∆F values for three traits (cocoon weight, shell weight and

pupation rate percentage) out of seven traits assessed. MU1 showed a lowest ∆F value

for filament length, whereas MU11 for larval weight. All the traits analyzed recorded

positive non-significant ∆F values (P>0.05) by their higher standard error values

indicating the absence of inbreeding depression in the selected populations.

Table-11 reveals the effects of inbreeding through average inbreeding

coefficient values and mean values analyzed for seven economic traits in selected

populations of four bivoltine breeds reared in six consecutive rearings during three

seasons of the year. Based on the results recorded in Table-11, the larval weight

showed maximum ∆F value (0.41±2.22) in CSR2 breed and a lowest ∆F value

(0.31±1.53) was noticed in NB4D2 breed. The intermediary ∆F values of 0.38±1.39

and 0.32±1.31 were expressed by MU854 and MG408 breeds. Because of the higher

standard error values recorded that the inbreeding effects are non-significant (P>0.05)

for these traits. The scrutiny of the results evidenced that the trait larval duration

19

exhibited highest ∆F value of 0.48±8.08 in NB4D2 breed followed by CSR2

(0.46±6.52), MU854 (0.44±6.98) and a lowest ∆F value of 0.41±8.04 in MG408 breed.

The breeds MG408 and MU854 evidenced lowest ∆F value for cocoon weight

(0.001±0.046) and (0.010±0.048) respectively, whereas highest ∆F value

(0.050±0.057) was recorded for the breed CSR2 and intermediary ∆F value of

0.045±0.046 by NB4D2 breed. It is quite interesting that the character shell weight

expressed lowest ∆F value (0.003±0.013) in CSR2 breed followed by 0.009±0.036

(MG408) 0.009±0.015 (MU854) and a highest ∆F value of 0.017±0.028 in NB4D2 breed.

The trait shell ratio (%) expressed highest ∆F value (0.04±0.77) in the breeds NB4D2

and CSR2 (0.04±0.25) and lowest ∆F values in MG408 (0.01±0.95), whereas MU854

breed exhibited ∆F values of 0.03±0.54. The high standard error values over the mean

values for these traits confirmed the insignificant (P>0.05) inbreeding effect thereby

indicating the absence of inbreeding depression. The popular breed NB4D2 recorded a

lowest ∆F value of 0.07±0.84 for pupation rate percentage followed by 0.07±1.14

(MG408) 0.08±0.96 (MU854) and a highest ∆F value of 0.09±1.566 were noticed in

CSR2 breed. The ∆F value for the trait filament length ranked first in MU854

(0.17±5.77) followed by NB4D2 (0.16±7.43), CSR2 (0.14±2.08) and a lowest ∆F value

in MG408 breed (0.12±7.42). The results clearly demonstrates ∆F values which are

non-significant (P>0.05) for the traits assessed and confirms the absence of inbreeding

depression in the selected populations.

Summarizing the results of Table-11 and figures 14-20 it is clear that. MG408

breed recorded lowest ∆F values for the four traits namely larval duration, cocoon

weight, shell ratio (%) and filament length, whereas MU854 registered intermediary ∆F

values for majority of the characters analyzed. In regard to CSR2 breed shell weight

revealed lowest ∆F value and the characters larval weight and pupation rate showed

minimum ∆F values by NB4D2 breed. Higher standard error values were recorded

over mean values for all the traits computed. Hence non-significant (P>0.05)

inbreeding effects proves the absence of inbreeding depression in the selected

populations.

The data pertaining to the narrow sense heritability percentage (h2%) of seven

quantitative traits in regard to the four multivoltines and four bivoltines along with

phenotypic coefficient of variance (PCV), genotypic coefficient of variance (GCV)

20

values and genetic advance (GA) for three different seasons of the year is presented in

Tables 12 and 13. The overall mean values along with standard errors for the above

breeds/race are presented in Table 14 and depicted in Figures 21-27.

Table-12 reveals the data related to PCV, GCV, narrow sense heritability

percentage (h2%) and GA percentages of four multivoltines (MU1, MU11, MU303 &

Pure Mysore) for seven quantitative characters during pre-monsoon, monsoon and

post-monsoon seasons. The data clearly indicates that during pre-monsoon season for

MU1 breed, PCV ranges from 0.58% (shell ratio (%)) to 0.99% (larval duration and

pupation rate %). On the other hand, the GCV (%) ranges from a lowest of 0.06 for

the traits (pupation rate and larval duration) to a highest of 0.48 for the trait filament

length. In regard to h2 values, it ranges from 6.55% (pupation rate) to a highest of

55.08% (filament length). A similar trend was observed in monsoon and post-

monsoon season wherein a highest heritability of 61.97% and 58.08% was clearly

evident for the trait filament length and a lowest of 7.52 and 6.82 for the trait pupation

rate during monsoon and post-monsoon seasons. The genetic advance recorded a

highest value of 8.45 for the trait cocoon weight and a lowest of 0.05 for the trait shell

weight in pre-monsoon, 9.30 (cocoon weight) and 0.06 (shell weight) in monsoon and

7.07 (filament length) and 0.04 (shell weight) in post-monsoon season.

The components of genetic variation such as PCV, GCV, h2, along with the

GA for seven economic traits of MU11 breed analyzed for three seasons clearly

indicates that the highest h2 of 62.87% is recorded for the trait filament length during

monsoon followed by 59.03% in post-monsoon and 57.63% during pre-monsoon

season. The traits larval weight, cocoon weight and shell weight also recorded highest

h2 (%) of 43.50, 47.05 and 45.01 during monsoon season. The intermediary h2 (%) of

24.12, 22.82 and 21.08 are noticed for shell ratio (%) during monsoon followed by

post-monsoon and pre-monsoon seasons. Similarly, the traits larval duration and

pupation rate exhibited a lowest h2 of 6.25% and 6.25% during pre-monsoon season.

Based on the results relating to genetic advance, the cocoon weight showed a highest

genetic advance value of 10.12 during monsoon season, whereas a lowest value of

0.05 is clearly evident for the trait shell weight during post-monsoon season. It is

important to note a comparison between the PCV and GCV values in the MU11 breed

wherein, the PCV values are always on the higher side than those of the values

recorded by GCV.

21

The same Table embodies the data related to narrow sense heritability (h2) of

seven quantitative traits in the multivoltine breed MU303 during three seasons. The h2

values based on PCV and GCV clearly demonstrated that the monsoon season greatly

influenced the expression of all the three genetic components namely PCV, GCV and

h2. It is interesting to note that the filament length recorded the highest h2 values

(53.10) in monsoon followed by 51.39 in post-monsoon and 50.59 in the pre-monsoon

season. The highest h2 percentage is exhibited by larval weight, cocoon weight and

shell weight, whereas larval duration and pupation rate recorded lowest h2 (%). The

intermediary h2 (%) is expressed by MU303 for the trait shell ratio (%). The lowest and

highest value for genetic advance was noticed for shell weight and cocoon weight

characters in all the three seasons. During pre-monsoon season it ranges from 0.05 to

8.11; 0.05 to 8.42 during monsoon season while, the same genetic parameter ranged

between 0.05 to 8.32 during post-monsoon season.

The data pertaining to the mean values, PCV, GCV and estimation of

heritability percentages along with the values related to genetic advance for seven

quantitative traits in the Pure Mysore race which is also tabulated in Table-12 clearly

indicated that the monsoon season is the most favorable season than those of the post-

monsoon and pre-monsoon season for the expression of seven quantitative traits under

study. The table also indicates that PCV percentage evidenced lower and higher

values for shell ratio (%) and pupation rate irrespective of the season. It ranges from

0.54 to 0.99 during pre-monsoon season, 0.55 to 0.99 during monsoon season, and

0.55-0.99 during post-monsoon season. The maximum and minimum GCV values are

expressed for the traits larval duration and filament length. It ranges between 0.04 and

0.23, 0.05-0.25 and 0.05-0.24 during pre-monsoon, monsoon and post-monsoon

season respectively.

The estimation of heritability values clearly indicated a general trend of above

30% for the three traits namely larval weight, cocoon weight and shell weight,

whereas for the trait filament length, the data has clearly indicated greater than 40%

during all the three seasons. Similarly, the shell ratio (%) character showed

intermediary values. The lower and higher values of genetic advance for the

parameters shell weight and cocoon weight ranged from 0.03 to 5.02 during pre-

monsoon season and 0.01 to 5.00 in monsoon and 0.01 to 5.11 during post- monsoon

season respectively.

22

Table-13 (Fig. 21-27) demonstrate the data related to the phenotypic

coefficient variability, genotypic coefficient variability, narrow sense heritability

percentages and genetic advance among four bivoltine breeds namely MG408, MU854,

CSR2 and NB4D2for seven quantitative traits in three seasons of the year. The scrutiny

of the data reveals highest PCV values for the traits pupation rate, larval duration and

cocoon weight during all the three seasons for MG408 breed. Lowest values of 0.602,

0.603 and 0.605 were observed for the trait shell ratio (%) during pre-monsoon, post-

monsoon and monsoon seasons respectively. The maximum GCV values were

exhibited by the trait filament length, whereas the minimum values were evidenced by

the trait pupation rate. The highest narrow sense heritability percentage of 63.50 was

recorded for the trait filament length during monsoon season, followed by post-

monsoon (61.64) and pre-monsoon (58.07). Lowest narrow sense heritability values

were recorded for the traits pupation rate and larval duration in all the seasons,

whereas shell ratio evidenced moderate heritability values. Genetic advance of 10.97

percentages was registered for cocoon weight during monsoon followed by 10.87 and

10.78 during pre- monsoon and post- monsoon seasons respectively.

The PCV, GCV, narrow sense heritability and genetic advance values

expressed maximum variations during monsoon season by MU854 breed for the

economic traits under study during pre-monsoon, monsoon and post monsoon seasons

Table-13). The highest heritability percentage was recorded for the trait filament

length and the lowest heritability percentage is expressed for the trait pupation rate

irrespective of the seasons. A minimum and maximum genetic advance percentage of

values range between 0.05-10.61 during pre-monsoon, 0.06-10.71 during monsoon,

whereas in post-monsoon season it ranges from 0.06-10.45 for the traits shell weight

and cocoon weight respectively.

A careful observation of the data in Table-13 for CSR2 breed clearly indicated that the PCV values are always excelled the GCV values by their higher percentages in all the three seasons of the year. PCV value of 0.99 was evidenced for the trait larval duration and pupation rate during monsoon season, whereas the lowest of 0.58 is recorded during pre-monsoon season for the trait shell ratio (%). On the other hand GCV values ranges from a lowest of 0.08 percentages for the traits pupation rate and larval duration (pre-monsoon season) and a highest 0f 0.59% for the trait filament

23

length (monsoon season).The data pertaining to narrow sense heritability which is estimated as the ratio between PCV and GCV clearly demonstrated highest h2 percentage of above 60% for the trait filament length in all the three seasons of the year followed by fifth instar larval weight, cocoon weight and shell weight which has revealed values above 40%. The remaining traits revealed the h2 values ranging from a minimum of 8.52 for pupation rate during pre-monsoon season to 10.11 for larval duration during monsoon season. A similar trend was observed for the parameter GA wherein the two important traits namely cocoon weight (11.22) and filament length (10.82) exhibited higher GA values compared to the other traits during pre-monsoon, whereas in monsoon season GA value is 11.73 and 10.91 for cocoon weight and filament length. During post-monsoon season the GA values were 11.65 for cocoon weight and 9.92 for filament length. Genetic advance values range from 0.07 to 4.22 for all the other traits.

Perusal of the data in Table-13 for NB4D2 during pre-monsoon season for PCV clearly demonstrated that a lowest value of 0.59 is for the trait shell ratio (%) and a highest of 0.99 is evident for the trait pupation rate. Though similar trend was observed in monsoon and post-monsoon season it is obvious that a highest value of 0.99 is recorded for the trait larval duration and pupation rate during monsoon season. In post-monsoon the value range from 0.60 (shell ratio (%)) to 0.99 (larval duration).The values of GCV is distinct in all the seasons which range from a minimum of 0.07 for the trait pupation rate during pre-monsoon season to a highest of 0.54 for the trait filament length during monsoon season. The data in regard to the narrow sense heritability clearly demonstrated a significant increase in the h2 values during monsoon season followed by post-monsoon and pre-monsoon season, thereby highlighting influence of environmental factors for the expression of the heritability values. The data in regard to genetic advance clearly indicated that the NB4D2 breed is unique by scoring GA values above 10 for only one trait namely cocoon weight followed by filament length in all the three seasons of the year. The remaining four traits recorded lower GA values for this genetic parameter and the lowest GA value was noticed for the trait shell weight.

Table-14 represents the pooled data pertaining to the narrow sense heritability for seven quantitative traits in each of the four multivoltine and four bivoltine breeds/race during three seasons. The overall picture that emerges out from the results clearly demonstrates that all the three multivoltines recorded the highest h2 values

24

compared to Pure Mysore, whereas bivoltine breed CSR2 ranked first by recording higher h2 values followed by MG408, MU854 and NB4D2 for most of the traits observed. The trait filament length is very distinct with highest h2 value of 61.96 in CSR2 breed and a lowest of 41.94 in Pure Mysore race. The graphical representations of the pooled data in regard to narrow sense heritability percentage for each of the seven economic traits for eight breeds/race are presented in Figures 21-27. The histograms clearly indicate that the bivoltines have higher h2 values than multivoltines.

The data on multiple trait evaluation indices along with average evaluation index value for thirteen quantitative traits of eight breeds/race in pre-monsoon, monsoon and post- monsoon seasons and overall mean values of three seasons is shown in Tables15 and 16 and depicted in Figures 28-40.

The data of evaluation index including average value in each of the four multivoltine breeds/race for thirteen economic traits for three seasons along with means are presented in Table-15. Scrutiny of the data during pre-monsoon season indicated that MU11 excelled over the other three multivoltines by recording highest average evaluation index value of 55.93 followed by 53.36 (MU1), 50.31(MU303). The PM race recorded 41.16. It is important that the Pure Mysore race recorded highest evaluation index values for yield by number, pupation rate and denier among multivoltines. During monsoon season, among the four multivoltines the Pure Mysore race recorded lowest average evaluation index value of 42 to a highest of 56.21 in MU11 breed. During post-monsoon season, among the four multivoltines MU11 breed recorded highest evaluation index value of 55.10 followed by MU1 (54.70) and MU303

(50.12). Though the Pure Mysore race recorded lowest average evaluation index value of 41.20 the three characters yield by number, pupation rate percentage and denier evidenced higher values of 66.56, 59.75 and 63.33 respectively.

Table-15 incorporates the data pertaining to the average evaluation index values for thirteen quantitative traits in each of the four bivoltines along with the means of three seasons. The overall picture that emerges from the data clearly demonstrates that among the multivoltines MU11 breed recorded the highest evaluation index value of 55.74 followed by MU1 (54.14) and MU303 (50.59) and Pure Mysore race (41.32). The results presented as histograms (Fig 28 - 40) clearly demonstrated that the evolved breeds and Pure Mysore race are equally good for specific quantitative traits compared

25

to bivoltines. It is important that Pure Mysore exhibited higher evaluation index values of >50 for yield by number, pupation rate and denier.

The data in Table-16 pertaining to four bivoltines during pre-monsoon season revealed a different picture, wherein all the four revealed a higher evaluation index value. It is clear that the highest average EI value of 53.38 is recorded by CSR2 breed followed by MG408 (52.56), MU854 (51.98) and NB4D2 (50.11). During monsoon season among the four bivoltines CSR2 ranked first with a highest average evaluation index value of 57.37 followed by MG408, (56.68) MU854 (52.84) and NB4D2 (51.58). During post-monsoon season, among the four bivoltines CSR2 breed exhibited highest average evaluation index values of 55.20 compared to the other three MG408, (54.33) MU854 (52.06) and NB4D2 (50.67).and lowest for larval duration, pupation rate and yield by number. The average evaluation index values of three seasons in Table-16 demonstrated that among bivoltine breeds CSR2 ranked first by recording higher evaluation index value of 55.29 followed by MG408 (54.70), MU854 (52.05) and NB4D2

(50.67).

Table-1 : Characteristic features of multivoltine breeds/race and bivoltine breeds

Breeds/ Race

Voltinism

Parentage Larval

Markings Cocoon colour

Cocoon shape

BR

EE

DS

MU1

Multivoltine

X-ray irradiation of Pure Mysore race

Plain larvae Greenish yellow Oval

MU11

Multivoltine Inbreeding the hybrids

of Pure Mysore x NB18Plain larvae Greenish

yellow Oval

MU303 Multivoltine Chemical mutagenesisPure Mysore x NB18

Plain larvae Greenish yellow Oval

Pure Mysore race (PM) Multivoltine -----

Plain larvae

Greenish yellow Spindle

BR

EE

DS

MG408

Bivoltine (GNP x C.nichi)

x (S9 x CC1) Plain larvae White Oval

MU854

Bivoltine (MG509 x S9)

x NB18 Plain larvae White Dumb-bell

CSR2

Bivoltine Shunrei

x Shogetsu Plain larvae White Oval

NB4D2

Bivoltine (Kokko x Suhato)

x (N124 x C124) Plain larvae White Dumb-bell

26

Table-2 : Mean values of the thirteen quantitative traits in four multivoltines during pre-monsoon season

Quantitative traits

Breeds/race

Fecundity (No.)

Hatching (%)

Weight of single V instar larva (g)

Larval duration

(h)

Yield/10,000 larvae brushed Single

cocoon weight

(g)

Single shell

weight (g)

Shell ratio (%)

Pupationrate (%)

Filament length

(m)

Denier (d)

Renditta (kg)

By number

By weight

(kg)

MU1 510

± 12.62

98.77

± 5.71

2.74

± 0.30

510

± 13.27

9649

± 58.51

10.46

± 1.82

1.202

± 0.519

0.184

± 0.002

15.30

± 2.23

94

± 5.67

531

± 13.38

2.05

± 0.81

11.30

± 1.92

MU11 514

± 13.22

98.39

± 5.71

2.70

± 0.30

512

± 13.07

9630

± 57.33

11.44

± 1.91

1.215

± 0.577

0.189

± 0.003

15.55

± 2.22

94

± 5.58

535

± 13.45

2.08

± 0.81

10.71

± 1.82

MU303 501

± 13.21

98.77

± 5.62

2.68

± 0. 29

516

± 13.10

9554

± 59.29

10.75

± 1.90

1.200

± 0.517

0.180

± 0.003

15.00

± 2.22

91

± 5.52

525

± 13.43

2.08

± 0.82

11.20

± 1.91

PM 417

± 12.24

97.89

± 5.70

2.18

± 0. 27

629

± 14.49

9710

± 62.58

9.72

± 1.71

1.081

± 0.579

0.138

± 0.006

12.76

± 2.01

95

± 5.64

333

± 10.81

2.02

± 0.81

13.38

± 2.07

Overall Mean

± SE

468

±14.87

97.28

±0.49

2.56

± 0.32

543.75

± 18.64

9641.25

± 21.16

10.64

± 0.27

1.170

± 0.022

0.171

± 0.023

14.57

± 0.51

93.62

± 0.60

481

± 34.89

2.05

± 0.08

11.66

± 0.40

CD @ 5% 12.87 1.77 0.14 12.19 87.62 0.21 0.08 0.001 0.60 1.79 15.64 0.003 0.38

27

Table-3 : Mean values of the thirteen quantitative traits in four multivoltines during monsoon season

Quantitative traits

Breeds /race

Fecundity (No.)

Hatching (%)

Weight of single V instar larva (g)

Larval duration

(h)

Yield/10,000 larvae brushed Single

cocoon weight

(g)

Single shell

weight (g)

Shell ratio (%)

Pupation rate (%)

Filament length

(m)

Denier (d)

Renditta (kg)

By number

By weight

(kg)

MU1 526

± 13.39

97.99

± 5.70

2.89

± 0.30

535

± 13.41

9710

± 65.26

12.56

± 2.00

1.317

± 0.577

0.214

± 0.007

16.25

± 2.30

96

± 5.79

551

± 13.56

2.08

± 0.81

10.06

± 1.72

MU11 530

± 13.50

97.72

± 5.74

3.02

± 0.31

536

± 13.43

9714

± 58.22

12.61

± 2.01

1.315

± 0.586

0.217

± 0.009

16.50

± 2.31

95

± 5.67

552

± 13.60

2.03

± 0.81

10.05

± 1.33

MU303 502

± 13.32

98.65

± 5.65

2.96

± 0.31

540

± 13.43

9608

± 56.66

12.48

± 2.00

1.310

± 0.594

0.216

± 0.008

16.48

± 2.31

94

± 5.61

550

± 13.60

2.01

± 0.81

10.95

± 1.87

PM 449

± 12.42

98.16

± 5.71

2.36

± 0.27

646

± 14.77

9774

± 58.90

9.97

± 1.73

1.110

± 0.596

0.142

± 0.008

12.79

± 2.04

96

± 5.65

348

± 10.84

2.01

± 0.80

12.10

± 2.00

Overall Mean ± SE

511.37

± 15.39

97.32

± 0.24

2.79

± 0.29

562.62

± 19.57

9697.62

± 22.40

11.88

± 0.45

1.266

± 0.036

0.197

± 0.012

15.51

± 0.56

95.25

± 0.44

500.37

± 35.32

2.04

± 0.01

10.80

± 0.34

CD @ 5% 19.37 1.57 0.14 10.34 95.22 0.22 0.020 0.001 0.36 1.79 13.56 0.003 0.25

28

Table-4 : Mean values of the thirteen quantitative traits in four multivoltines during post-monsoon season

Quantitative traits

Breeds/race

Fecundity (No.)

Hatching (%)

Weight of single V instar larva (g)

Larval duration

(h)

Yield/10,000 larvae brushed Single

cocoon weight

(g)

Single shell

weight (g)

Shell ratio (%)

Pupation rate (%)

Filament length

(m)

Denier (d)

Renditta (kg)

By number

By weight

(kg)

MU1 514

± 13.35

98.81

± 5.73

2.84

± 0.30

540

± 13.22

9614

± 56.73

11.54

± 1.65

1.252

± 0.536

0.201

± .005

16.05

± 2.29

95

± 5.64

544

± 13.47

2.04

± 0.81

10.58

± 1.74

MU11 516

± 13.58

97.59

± 5.71

2.79

± 0.30

540

± 13.59

9566

± 57.14

11.98

± 1.96

1.291

± 0.574

0.208

± .006

16.11

± 2.25

95

± 5.64

540

±13.57

2.05

± 0.81

10.47

± 1.48

MU303 526

± 13.23

98.86

± 5.67

2.76

± 0.29

536

± 13.64

9582

± 56.88

11.59

± 1.91

1.236

± 0.552

0.194

± .003

15.69

± 2.23

92

± 5.50

538

± 13.48

2.08

± 0.81

10.98

± 1.87

PM 440

± 12.24

96.80

± 5.67

2.39

± 0.27

656

± 17.89

9674

± 56.87

9.88

±1.73

1.093

± 0.581

0.140

± .007

12.80

± 3.46

95

± 5.64

339

± 10.85

2.01

± 0.80

12.31

± 2.00

Overall Mean

± SE

507.12

± 15.66

97.22

± 0.31

2.72

± 0.30

567.37

± 21.62

9606

± 19.47

11.21

± 0.32

1.218

± 0.029

0.185

± .010

15.23

± 0.51

94

± 0.60

491

± 34.67

2.04

± 0.01

11.06

± 0.29

CD @ 5% 15.88 1.62 0.35 8.95 67.33 0.98 0.004 0.010 0.44 2.07 25.70 0.004 0.41

29

Table-5 : Data of the thirteen quantitative traits of four multivoltine breeds/race (Mean of three seasons)

Quantitative traits

Breeds /race

Fecundity (No.)

Hatching (%)

Weight of single V instar larva (g)

Larval duration

(h)

Yield/10,000 larvae brushed Single

cocoon weight

(g)

Single shell

weight (g)

Shell ratio (%)

Pupation rate (%)

Filament length

(m)

Denier (d)

Renditta (kg)

By number

By weight

(kg)

MU1 516.66

± 14.53

98.52

± 4.03

2.82

± 0.22

528.33

±10.04

9657.66

±40.41

11.52

±1.39

1.257

±0.408

0.199

±0.003

15.83

±1.62

94.33

±3.98

542.16

±10.23

2.05

±0.57

10.64

±1.32

MU11 520.00

±14.57

97.90

±4.02

2.83

±0.22

529.33

±0.30

9636.66

±45.19

12.01

±1.38

1.274

±0.408

0.204

±0.003

16.01

±1.62

94.66

±3.99

542.33

±9.99

2.05

±0.57

10.41

±1.29

MU303 509.66

±13.64

98.59

±4.00

2.80

± 0.21

530.66

±10.32

9581.33

±41.39

11.60

±1.39

1.248

±0.408

0.196

±0.002

15.70

±1.61

92.33

±3.94

537.66

±10.09

2.05

±0.57

11.04

±1.32

PM 435.33

±10.66

97.78

±4.03

2.31

± 0..19

643.66

±12.24

9719.33

±42.85

9.86

±1.22

1.094

±0.408

0.140

±0.001

12.81

±1.45

95.33

±4.00

340

±8.40

2.01

±0.57

12.60

±1.44

Overall Mean

± SE

495.41

± 23.35

98.19

± 0.47

2.69

± 0.14

557.99

± 32.79

9648.74

± 32.92

11.24

± 0.54

1.218

± 0.048

0.184

± 0.017

15.08

± 0.87

94.16

± 0.81

490.54

± 57.95

2.04

± 0.01

11.17

± 0.56

CD @ 5% 35.87 1.66 0.15 24.01 88.66 1.18 0.009 0.002 0.98 1.97 24.81 0.003 0.68

30

Table-6 : Mean values of the thirteen quantitative traits in four bivoltines during pre-monsoon season

Quantitative traits

Breeds

Fecundity (No.)

Hatching (%)

Weight of single V instar larva (g)

Larval duration

(h)

Yield/10,000 larvae brushed Single

cocoon weight

(g)

Single shell

weight (g)

Shell ratio (%)

Pupation rate (%)

Filament length

(m)

Denier (d)

Renditta (kg)

By number

By weight

(kg)

MG408 532

± 13.41

96.78

± 5.67

4.33

± 0.37

536

± 13.41

9552

± 63.26

16.22

± 2.30

1.776

± 0.572

0.337

± 0.004

18.96

± 2.44

92

± 5.58

881

± 17.43

2.48

± 0.81

8.46

± 1.63

MU854 530

± 13.49

97.19

± 5.68

4.38

± 0.38

538

± 13.39

9500

± 61.00

16.21

± 2.30

1.752

± 0.576

0.322

± 0.006

18.13

± 2.38

92

± 5.52

791

± 16.33

2.45

± 0.80

8.91

± 1.68

CSR2 546

± 13.16

93.68

± 5.64

4.62

± 0.40

565

± 13.77

9349

± 59.18

16.64

± 2.30

1.901

± 0.577

0.385

± 0.009

20.25

± 2.57

89

± 5.55

998

± 18.60

2.45

± 0.89

7.56

± 1.52

NB4D2 525

± 13.01

96.02

± 5.64

4.21

± 0.37

545

± 13.51

9462

± 56.18

15.85

± 2.33

1.769

± 0.577

0.332

± 0.011

18.76

± 2.41

92

± 5.54

860

± 17.01

2.43

± 0.87

9.16

± 1.73

Overall Mean

± SE

523.25

± 4.90

96.17

± 0.25

4.39

± 0.38

545.50

± 4.78

9456.87

± 44.78

16.13

± 0.144

1.825

± 0.023

0.342

± 0.009

18.75

± 0.30

91

± 0.49

877.25

± 37.21

2.46

± 0.01

8.54

± 0.247

CD @ 5% 17.17 1.06 0.19 9.86 88.73 0.19 0.010 0.001 0.79 2.06 21.31 0.004 0.24

31

Table-7 : Mean values of the thirteen quantitative traits in four bivoltines during monsoon season

Quantitative traits

Breeds

Fecundity (No.)

Hatching (%)

Weight of single V instar larva (g)

Larval duration

(h)

Yield/10,000 larvae brushed Single

cocoon weight

(g)

Single shell

weight (g)

Shell ratio (%)

Pupation rate (%)

Filament length

(m)

Denier (d)

Renditta (kg)

By number

By weight

(kg)

MG408 561

± 13.82

97.10

± 5.71

4.65

± 0.30

563

± 13.73

9702

± 59.99

18.47

± 2.45

1.990

± 0.653

0.420

± 0.013

21.10

± 2.58

95

± 5.65

1006

± 18.40

2.35

± 0.82

7.53

± 1.51

MU854 551

± 13.67

95.60

± 5.64

4.57

± 0.38

566

± 13.73

9680

± 57.37

17.61

± 2.38

1.886

± 0.589

0.367

± 0.011

19.45

± 2.52

95

± 5.61

931

± 17.18

2.43

± 0.80

8.03

± 1.68

CSR2 565

± 13.48

95.76

± 5.68

5.20

± 0.41

568

± 13.80

9481

± 60.23

18.66

± 2.48

2.155

± 0.576

0.457

± 0.013

21.20

± 2.65

92

± 5.56

1061

± 18.67

2.43

± 0.82

7.13

± 1.31

NB4D2 550

± 14.03

96.00

± 5.67

4.63

± 0.39

550

± 13.61

9690

± 57.39

17.52

± 2.38

1.881

± 0.582

0.368

± 0.023

19.56

± 2.22

95

± 5.62

903

± 26.49

2.38

± 0.86

8.32

± 1.63

Overall Mean ± SE

554

± 2.13

97.12

± 0.28

4.75

± 0.38

559.37

± 3.18

9643.50

± 37.76

18.04

± 0.20

1.960

± 0.048

0.398

± 0.015

20.30

± 0.37

94

± 0.374

972

± 26.07

2.402

± 0.01

7.82

± 0.19

CD @ 5% 12.87 1.18 0.14 9.86 86.23 0.99 0.016 0.011 0.52 1.46 18.05 0.003 0.27

32

Table-8 : Mean values of the thirteen quantitative traits in four bivoltines during post-monsoon season

Quantitativetraits

Breeds

Fecundity (No.)

Hatching (%)

Weight of single V instar larva (g)

Larval duration

(h)

Yield/10,000 larvae brushed Single

cocoon weight

(g)

Single shell

weight (g)

Shell ratio (%)

Pupation rate (%)

Filament length

(m)

Denier (d)

Renditta (kg)

By number

By weight

(kg)

MG408 546

± 13.57

96.65

± 5.65

4.55

± 0.39

565

± 13.98

9592

± 58.10

17.37

± 2.38

1.880

± 0.617

0.378

± 0.010

20.10

± 2.51

94

± 5.59

990

± 18.63

2.42

± 0.81

8.17

± 1.55

MU854 540

± 13.51

97.91

± 5.81

4.49

± 0.38

565

± 13.74

9494

± 56.31

17.08

± 2.34

1.884

± 0.558

0.358

± 0.010

18.47

± 2.51

94

± 5.62

898

± 17.19

2.42

± 0.80

8.61

± 1.69

CSR2

544

± 13.77

93.54

± 5.53

5.06

± 0.41

594

± 14.27

9301

± 59.76

17.80

± 2.38

2.000

± 0.574

0.396

± 0.006

20.55

± 2.58

91

± 5.52

999

± 18.54

2.46

± 0.89

7.31

± 1.51

NB4D2 541

± 14.04

95.12

± 5.64

4.33

± 0.36

554

± 13.62

9488

± 56.84

16.97

± 2.22

1.878

± 0.532

0.345

± 0.010

18.37

± 2.33

94

± 5.66

855

± 17.47

2.42

± 0.87

8.92

± 1.64

Overall Mean

± SE

554

± 2.13

97.12

± 0.28

4.75

± 0.38

559.37

± 3.18

9643.50

± 37.76

18.04

± 0.20

1.960

± 0.048

0.398

± 0.015

20.30

± 0.37

94

± 0.37

972

± 26.07

2.40

± 0.01

7.82

± 0.19

CD @ 5% 12.87 1.18 0.14 9.86 86.23 0.99 0.01 0.01 0.52 1.46 18.05 0.003 0.27

33

Table-9 : Data of the thirteen quantitative traits in four bivoltine breeds (Mean of three seasons)

Quantitative traits

Breeds

Fecundity (No.)

Hatching (%)

Weight of single V instar larva (g)

Larval duration

(h)

Yield/10,000 larvae brushed Single

cocoon weight

(g)

Single shell

weight(g)

Shell ratio (%)

Pupation rate (%)

Filament length

(m)

Denier (d)

Renditta (kg)

34

By number

By weight

(kg)

MG408 546.33

± 11.05

96.82 ±

4.03

4.51 ±

0.27

554.66 ±

11.23

9615.83 ±

49.26

17.30 ±

1.71

1.882 ±

0.466

0.378 ±

0.003

20.08 ±

1.85

93.00 ±

3.97

959.83 ±

32.93

2.42 ±

0.57

8.00 ±

1.14

MU854 540.33

± 10.96

96.00 ±

3.99

4.48 ±

0.27

556.16 ±

11.03

9558.00 ±

53.70

16.94 ±

1.67

1.848 ±

0.408

0.349 ±

0.004

18.88 ±

1.79

93.00 ±

3.96

873.66 ±

26.82

2.44 ±

0.57

8.51 ±

1.17

CSR2 551.66

± 11.63

94.30 ±

4.00

4.96 ±

0.30

575.33 ±

10.69

9377.00 ±

53.20

17.66 ±

1.71

2.016 ±

0.540

0.412 ±

0.003

20.43 ±

1.85

90.83 ±

3.93

1019 ±

17.19

2.44 ±

0.57

7.33 ±

1.08

NB4D2 538.33

± 11.26

95.71 ±

4.01

4.39 ±

0.27

549.16 ±

10.09

9546.83 ±

61.20

16.69 ±

1.68

1.842 ±

0.538

0.345 ±

0.004

18.72 ±

1.76

93.66 ±

3.95

872.50 ±

24.58

2.41 ±

0.57

8.80 ±

1.20

Overall Mean ± SE

544.16 ±

1.88

96.93 ±

0.21

4.58 ±

0.28

558.83 ±

6.58

9524.41 ±

59.36

17.14 ±

0.24

1.897 ±

0.046

0.371 ±

0.017

19.55 ±

0.49

92.25 ±

0.62

931.24 ±

41.21

2.43 ±

0.007

8.21

0.77

CD @ 5% 23.34 1.07 0.21 17.97 96.22 1.47 0.10 0.04 1.41 1.74 63.89 0.005 0.40

400

420

440

460

480

500

520

540

560

Fec

un

dit

y (N

o.)

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

Lar

val w

eigh

t (g

)

M

9200

9300

9400

9500

9600

9700

9800

Yie

ld b

y n

um

ber

M

F

Fig.

Fig.

Fif

Multivoltines

Multivoltines

Multivoltines

Fig. 1: Mean valu

3: Mean values f

5: Mean values f

ig. 1-6 : Meanfour multivol

Bivoltines

Bivoltines

Bivoltines

93.5

94

94.5

95

95.5

96

96.5

97

97.5

98

98.5

Hat

chin

g (%

)

ues for Fecundity

for Larval weight

for Yield by numb

35

n values for tltine and four

s

s MMultivoltines Bivoltiness

Figg. 2: Mean valuess for Hatching   

500

520

540

560

580

600

620

640

660

680L

arva

l du

rati

on (

h)

MMultivoltines Bivoltines

(g)  

ber  

the quantitatir bivoltine br

5

7

9

11

13

15

17

19

Yie

ld b

y w

eigh

t (k

g)

M

Fig. 4: M

Fig. 6: M

ive traits in reeds/race

Multivoltines

Mean values for L

Mean values for Y

Bivoltines

Larval duration (hh)  

Yield by weight (kkg) 

1

1.2

1.4

1.6

1.8

2

2.2

Sing

le c

ocoo

n w

eigh

t (g

)

10

12

14

16

18

20

22

Shel

l per

cen

tage

300

400

500

600

700

800

900

1000

1100

Fila

men

t le

ngt

h

(m)

Fig. 7

Fig

Fig. 11

Figf

Multivoltines

Multivoltines

Multivoltines

7: Mean values fo

g. 9: Mean values

1: Mean values fo

g. 7-13 : Meafour multivol

Bivoltines

Bivoltine

Bivoltines

5

6

7

8

9

10

11

12

13

Ren

dit

ta(k

g)or Cocoon weight

for Shell ratio (%

or Filament length

Fig.

36

an values for ltine and four

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

Sin

gle

shel

l wei

ght

(g)

es

Multivoltines

t (g)  

%) 

h (m)  

13: Mean values

the quantitatr bivoltine br

90

91

92

93

94

95

96

Pu

pat

ion

rat

e (%

)

1.51.61.71.81.9

22.12.22.32.42.5

Den

ier(

d)

Bivoltin

Fig. 8

Fig. 10:

Fig.

for Renditta (kg)

tive traits in reeds/race

Multivoltines

Multivoltines

Multivoltines

nes

: Mean values for

Mean values for

. 12: Mean values

)  

Bivoltines

Bivoltines

Bivoltines

r Shell weight (g)

Pupation rate (%

s for Denier (d)  

%)  

 

Table-10 : Inbreeding coefficient (∆F) for seven quantitative traits in four multivoltine breeds /race (Mean of six rearings)

Quantitative traits

MU1 MU11 MU303 Pure Mysore

Mean ±SE (Inbreeding coefficient)

∆F Mean ±SE (Inbreeding

coefficient) ∆F Mean ±SE (Inbreeding coefficient)

∆F Mean ±SE

(Inbreeding coefficient)

∆F

Weight of single V instar larva (g)

2.82 ± 0.22

0.38 ± 0.83

2.83 ± 0.22

0.33 ± 0.93

2.80 ±0.21

0.38 ± 0.90

2.31 ±0.19

0.33 ± 0.92

Larval duration (h) 528.33 ±10.04

0.41 ± 11.11

529.33 ± 10.30

0.43 ± 10.60

530.66 ±10.32

0.41 ± 10.78

643.66 ±12.24

0.43 ± 5.35

Cocoon weight (g) 1.257 ± 0.40

0.042 ± 0.047

1.274 ±0.408

0.031 ± 0.055

1.248 ±0.410

0.041 ± 0.051

1.094 ±0.406

0.023 ± 0.057

Shell weight (g) 0.199

± 0.003 0.013

± 0.014 0.204

± 0.002 0.011

± 0.012 0.196

±0.003 0.007

± 0.009 0.140

±0.001 0.002

± 0.005

Shell ratio (%) 15.83 ±1.62

0.033 ± 0.403

16.01 ± 1.62

0.04 ± 0.43

15.70 ±1.61

0.05 ± 0.50

12.81 ± 1.45

0.03 ± 0.39

Pupation rate (%) 94.83 ± 3.98

0.06 ± 1.08

94.66 ± 3.99

0.06 ± 1.15

92.33 ±3.94

0.08 ± 1.31

95.33 ±4.00

0.004 ± 0.68

Filament length (m) 542.16 ±10.23

0.12 ± 10.11

542.33 ± 9.99

0.13 ± 10.35

537.66 ±10.09

0.16 ± 9.26

340.00 ± 8.40

0.17 ± 8.59

Rate of inbreeding was calculated using the formula Ft=∆F + (1-∆F) Ft-1 and inbreeding coefficient is recorded for the average data of

number of generations (Falconer- 1989).

37

38

Table-11 : Inbreeding coefficient (∆F) for seven quantitative traits in four bivoltine breeds (Mean of six rearings)

Quantitative traits MG408 MU854 CSR2 NB4D2

Mean ±SE (Inbreeding coefficient) ∆F Mean ±SE (Inbreeding

coefficient) ∆F Mean ±SE (Inbreeding coefficient) ∆F Mean ±SE (Inbreeding

coefficient) ∆F

Weight of single V instar larva (g)

4.51 ± 0.27

0.32 ± 1.31

4.48 ± 0.27

0.38 ± 1.39

4.96 ± 0.30

0.41 ± 2.22

4.39 ± 0.27

0.31 ± 1.53

Larval duration (h) 554.66 ±11.23

0.41 ± 8.04

556.16 ±11.03

0.44 ± 6.98

575.33 ± 10.69

0.46 ± 6.52

549.16 ± 10.09

0.48 ± 8.08

Cocoon weight (g) 1.88

± 0.46 0.001

± 0.046 1.848

± 0.408 0.010

± 0.048 2.016 ± 0.54

0.050 ± 0.06

1.842 ± 0.538

0.045 ± 0.046

Shell weight (g) 0.378

± 0.003 0.009

± 0.015 0.349

± 0.004 0.012

± 0.036 0.412

± 0.003 0.003

± 0.013 0.345

±0.004 0.017

± 0.028

Shell ratio (%) 20.08

± 1.85 0. 01

± 0. 95 18.88

± 1.79 0.03

± 0.54 20.43 ± 1.85

0.04 ± 0.25

18.72 ± 1.76

0.04 ± 0.77

Pupation rate (%) 93.00 ± 3.97

0.07 ± 1.14

93.00 ± 3.96

0.08 ± 0.96

90.83 ± 3.9

0.09 ± 1.56

93.66 ± 3.95

0.07 ± 0.84

Filament length (m) 959.83 ± 32.93

0.12 ± 7.42

873.66 ± 26.82

0.17 ± 5.77

1019.00 ± 17.15

0.14 ± 2.08

872.50 ± 24.58

0.16 ± 7.43

Rate of inbreeding was calculated using the formula Ft=∆F + (1-∆F) Ft-1 and inbreeding coefficient is recorded for the average data of

number of generations (Falconer- 1989).

0.38

0

0.0

0.0

0.0

0.0

0.03

0.

Fig. 14: In

Fig. 16: In

Fig. 18:

Fig. 14-20 : If

0

0.330.32

0.41

0.31

Larval w

0.02

01

01

05

0.04

Single cocoo

0

0.0301

.040.04

Shell rati

nbreeding coeffi

nbreeding coeffic

: Inbreeding coe

Inbreeding cofour multivol

0.38

0.33

0.38

weight

0.04

0.03

0.04

on weight

0.03

0.04

0.05

io 

0.17

0.1

icient (∆F) for la

cient (∆F)for co

efficient (∆F) for

Fig. 20: Inbre

39

o-efficient (Δltine and four

MU1MU11MU303PMMG408MU854CSR2NB4D2

0

0.44

0.46

MU1

MU11

MU303

PM

MG408

MU854

CSR2

NB4D2

MU1

MU11

MU303

PM

MG408

MU854

CSR2

NB4D2

0.12

0.180.12

50.16

Filament le

arval weight  

ocoon weight  

r shell %  

eeding coefficien

ΔF) for seven r bivoltine br

00.01

0.003

0.

0.09

0.1

2

0.13

0.17

ngth

Fig. 15: Inbreed

Fig. 17: Inbre

Fig. 19: Inbre

nt (∆F) for filam

economic trareeds/race

0.41

0.430.41

0.48

Larval durat

0.01

0.000.01

.02

Single shell w

0.06

0

0

00.08

0.07

Pupation ra

MU1

MU11

MU303

PM

MG408

MU854

CSR2

NB4D2

ding coefficient (

eeding coefficien

eeding coefficien

ment length  

aits in the

0.43

0.41

tion

MMMPMMCN

MU1MU11MU303M

MG408MU854CSR2NB4D2

(∆F) for larval d

0.01

0.01

02

weight

M

M

M

PM

M

M

CS

NB

0.06

0.08

0.004

ate

MU

MU

MU

PM

MG

MU

CSR

NB4

nt (∆F) for shell

t (∆F) for pupat

duration  

U1

U11

U303

M

G408

U854

SR2

B4D2

weight 

U1

U11

U303

G408

U854

R2

4D2

tion rate 

Table-12 : Narrow sense heritability percentage (h2) of seven quantitative traits in four multivoltine breeds/race during three seasons

40

Breeds/Race Quantitative traits

Pre-monsoon season Monsoon season Post-monsoon season

PCV (%)

GCV (%)

( h2) %

GA @

5 %

PCV (%)

GCV (%)

( h2) %

GA @ 5 %

PCV (%)

GCV (%)

( h2) %

GA @

5 %

MU1

Weight of single V Instar larva 0.79 0.30 37.93 3.06 0.80 0.31 39.50 4.72 0.80 0.30 38.08 3.53 Larval duration 0.99 0.06 6.91 3.54 0.99 0.08 8.93 3.24 0.99 0.07 7.43 3.26 Cocoon weight 0.78 0.32 41.29 8.45 0.83 0.37 45.07 9.30 0.83 0.36 43.87 7.03 Shell weight 0.62 0.25 40.93 0.05 0.65 0.27 42.24 0.06 0.66 0.27 41.14 0.04 Shell ratio (%) 0.58 0.12 20.74 2.28 0.57 0.13 23.87 2.60 0.58 0.12 21.17 2.33 Filament length 0.87 0.48 55.08 8.32 0.88 0.54 61.97 7.31 0.87 0.51 58.08 7.07 Pupation rate 0.99 0.06 6.55 3.89 0.99 0.07 7.52 3.40 0.99 0.06 6.82 3.27

MU11

Weight of single V Instar larva 0.81 0.31 38.28 3.17 0.81 0.35 43.50 4.81 0.81 0.33 41.23 3.72 Larval duration 0.89 0.05 6.25 3.68 0.81 0.07 8.84 3.33 0.91 0.06 7.08 3.28 Cocoon weight 0.84 0.36 43.40 9.41 0.84 0.39 47.05 10.12 0.84 0.38 45.14 8.12 Shell weight 0.63 0.26 41.39 0.06 0.66 0.29 45.01 0.07 0.65 0.28 43.62 0.05 Shell ratio (%) 0.55 0.12 21.08 2.29 0.60 0.14 24.12 2.51 0.57 0.13 22.82 2.44 Filament length 0.87 0.50 57.63 7.30 0.87 0.55 62.87 8.21 0.87 0.51 59.03 8.09 Pupation rate 0.99 0.06 6.25 3.90 0.99 0.08 8.24 3.52 0.99 0.07 7.35 3.27

MU303

Weight of single V Instar larva 0.78 0.27 35.41 3.00 0.77 0.31 40.02 4.44 0.78 0.29 37.53 3.43 Larval duration 0.78 0.04 6.09 3.12 0.79 0.06 8.57 3.15 0.79 0.05 7.45 3.16 Cocoon weight 0.77 0.31 40.92 8.11 0.78 0.32 42.12 8.42 0.77 0.32 41.44 8.32 Shell weight 0.60 0.23 39.10 0.05 0.61 0.25 41.40 0.05 0.60 0.24 40.78 0.05 Shell ratio (%) 0.56 0.11 19.68 2.16 0.59 0.13 22.12 2.52 0.57 0.12 20.76 2.61 Filament length 0.75 0.38 50.59 8.07 0.77 0.41 53.10 6.25 0.75 0.38 51.39 7.35 Pupation rate 0.99 0.07 7.26 3.78 0.99 0.08 8.30 3.32 0.99 0.07 7.66 3.01

Pure Mysore

Weight of single V Instar larva 0.65 0.20 30.79 2.52 0.66 0.22 33.03 2.32 0.64 0.20 31.42 2.62 Larval duration 0.79 0.04 5.63 2.63 0.78 0.05 7.10 2.22 0.78 0.05 6.75 2.34 Cocoon weight 0.66 0.23 34.98 5.02 0.66 0.24 37.00 5.00 0.65 0.23 36.17 5.11 Shell weight 0.59 0.20 33.95 0.03 0.59 0.21 35.96 0.01 0.59 0.20 34.29 0.01 Shell ratio (%) 0.54 0.09 16.78 1.11 0.55 0.11 20.18 1.00 0.55 0.10 18.14 1.01 Filament length 0.57 0.23 40.86 3.11 0. 58 0.25 43.66 3.23 0.58 0.24 41.30 3.24 Pupation rate 0.99 0.06 6.59 2.32 0.99 0.07 7.25 2.00 0.99 0.06 6.86 2.22

Table-13 : Narrow sense heritability percentage (h2) of seven quantitative traits in four bivoltine breeds during three seasons

41

Breeds/Race Quantitative traits

Pre-monsoon season Monsoon season Post-monsoon season

PCV (%)

GCV (%)

( h2) %

GA @

5 %

PCV (%)

GCV (%)

( h2) %

GA @ 5 %

PCV (%)

GCV (%)

( h2) %

GA @

5 %

MG408

Weight of single V Instar larva 0.85 0.41 48.18 3.77 0.87 0.46 53.09 3.86 0.86 0.44 51.56 3.84 Larval duration 0.99 0.08 8.32 3.67 0.99 0.10 10.01 3.88 0.99 0.09 9.23 3.87 Cocoon weight 0.93 0.43 46.63 10.87 0.94 0.46 49.25 10.97 0.93 0.45 48.71 10.78 Shell weight 0.71 0.25 35.36 0.06 0.73 0.30 41.06 0.07 0.72 0.28 39.47 0.06 Shell ratio (%) 0.605 0.14 24.58 3.32 0.60 0.16 27.27 3.41 0.60 0.15 26.03 3.39 Filament length 0.85 0.50 58.07 9.51 0.87 0.55 63.50 9.82 0.86 0.53 61.64 9.71 Pupation rate 0.89 0.07 8.07 4.12 0.98 0.09 9.43 3.98 0.98 0.09 8.79 3.82

MU854

Weight of single V Instar larva 0.84 0.40 47.33 3.32 0.85 0.44 52.04 3.52 0.85 0.43 50.52 3.44 Larval duration 0.99 0.08 8.36 3.42 0.99 0.09 9.34 3.52 0.99 0.08 8.66 3.47 Cocoon weight) 0.95 0.43 45.64 10.61 0.98 0.46 47.20 10.71 0.97 0.45 46.83 10.45 Shell weight 0.70 0.21 31.05 0.05 0.71 0.24 34.26 0.06 0.71 0.23 32.67 0.06 Shell ratio (%) 0.59 0.14 24.03 3.00 0.60 0.15 26.28 3.10 0.59 0.15 25.16 3.12 Filament length 0.98 0.57 58.01 9.72 0.95 0.58 61.74 9.93 0.97 0.58 60.10 9.53 Pupation rate 0.99 0.08 8.21 3.95 0.99 0.09 9.84 3.76 0.99 0.08 8.90 3.55

CSR2

Weight of single V Instar larva 0.84 0.43 50.82 3.76 0.85 0.46 54.03 3.98 0.85 0.44 52.58 3.75 Larval duration 0.99 0.08 8.54 3.89 0.99 0.10 10.11 4.00 0.99 0.09 9.43 3.93 Cocoon weight 0.90 0.43 48.00 11.22 0.90 0.49 54.43 11.73 0.90 0.46 51.49 11.65 Shell weight 0.69 0.26 38.27 0.07 0.72 0.30 42.85 0.07 0.71 0.29 40.69 0.07 Shell ratio (%) 0.58 0.14 25.12 3.52 0.61 0.17 28.64 3.81 0.60 0.16 27.86 3.28 Filament length 0.98 0.59 60.18 10.82 0.92 0.59 64.42 10.91 0.96 0.59 61.28 9.92 Pupation rate 0.99 0.08 8.52 4.22 0.99 0.09 10.00 3.98 0.99 0.09 9.04 3.72

NB4D2

Weight of single V Instar larva 0.82 0.38 47.20 3.12 0.86 0.43 50.11 3.22 0.85 0.41 48.00 3.21 Larval duration 0.99 0.08 8.58 3.02 0.99 0.09 9.26 3.13 0.99 0.08 8.77 3.10 Cocoon weight 0.87 0.39 44.68 10.00 0.91 0.44 48.79 10.53 0.91 0.42 46.39 10.14 Shell weight 0.67 0.21 31.30 0.06 0.71 0.25 35.16 0.07 0.71 0.24 33.84 0.06 Shell ratio (%) 0.59 0.14 24.07 3.06 0.60 0.15 26.07 3.121 0.60 0.15 25.12 3.11 Filament length 0.86 0.50 58.72 8.33 0.89 0.54 60.17 9.55 0.87 0.52 59.65 9.12 Pupation rate 0.98 0.07 7.73 3.78 0.99 0.09 9.27 3.91 0.98 0.08 8.32 3.72

42

Table-14 : Narrow sense heritability percentage of seven quantitative traits in four multivoltine and four bivoltine breeds/race (Mean of three seasons)

Quantitative

traits Breeds/Race

Weight of single V Instar larva (g)

Larval duration (h) Cocoon weight (g) Shell weight (g) Shell ratio (%) Pupation rate (%) Filament length (m)

Mean ± SE

h2 %

Mean ± SE

h2 %

Mean ± SE

h2 %

Mean ± SE

h2 %

Mean ± SE

h2 %

Mean ± SE

h2 %

Mean ± SE

h2 %

MU1 2.82

± 0.22 38.51

528.16 ± 10.04

7.76 1.257

± 0.407 43.41

0.199 ± 0.003

41.43 15.83 ± 1.62

21.93 94.83 ± 3.98

7.08 542.16 ± 10.23

58.51

MU11 2.83

±0.22 41.00

529.83 ± 10.30

7.39 1.274

± 0.408 45.19

0.204 ± 0.002

43.34 16.01 ± 1.62

22.67 94.66 ± 3.99

7.43 542.33 ±9.94 59.53

MU303 2.80

±0.21 37.65

530.16 ± 10.32

7.37 1.248

± 0.410 41.49

0.196 ± 0.003

40.43 15.65 ± 1.61

20.85 92.16 ± 3.94

7.81 537.66 ±10.09

51.69

Pure Mysore 2.31

±0.19 31.74

643.00 ± 12.24

6.49 1.094

± 0.406 36.05

0.140 ± 0.001

34.73 12.81 ± 1.45

18.37 95.33 ±4.00

6.97 340.00 ±8.40

41.94

MG408 4.51

±0.27 50.94

554.66 ± 11.23

9.30 1.882

± 0.466 48.19

0.378 ± 0.003

38.63 20.08 ± 1.85

25.96 93.00 ± 3.97

8.76 959.83 ± 32.93

60.93

MU854 4.48

±0.27 49.96

554.16 ± 11.03

8.79 1.848

± 0.408 46.56

0.349 ± 0.004

32.66 18.88 ± 1.79

25.16 93.00 ±3.96

8.99 873.66 ± 26.82

59.95

CSR2 4.96

±0.30 52.48

575.33 ± 10.69

9.40 2.016

± 0.540 51.31

0.412 ± 0.003

40.60 20.43 ± 1.85

27.20 90.83 ± 3.96

9.19 1019.00 ±17.19

61.96

NB4D2 4.39

±0.27 48.44

549.16 ± 10.09

8.87 1.842

± 0.538 33.29

0.345 ±0.004

33.43 18.72 ±1.76

25.09 93.16 ± 3.95

8.44 872.50 ±24.58

59.09

25

30

35

40

45

50

55

h2

%

Fig

30

35

40

45

50

55

h2%

12

17

22

27

32

h2%

Fig. 21

Fig. 2

Fig. 25

g. 22-27 : Nain the

1: Narrow senselarval

3: Narrow sensecocoon

5: Narrow senseshell ra

F

arrow sense e four multiv

35

40

45

50

55

60

65

h2%

e heritability (h2%weight  

e heritability (h2

n weight   

e heritability (h2%atio (%) 

Fig. 27: Narrow s

43

5

6

7

8

9

10

h2

%

heritability voltine and f

%) for

%) for

%) for

sense heritability

(h2%) for sfour bivoltin

3032343638404244

h2%

6

7

8

9

10

h2%

Fig. 22: Nar

Fig. 24: Na

Fig. 26: Nar

y (h2%) for filam

even quantine breeds/ra

rrow sense heritlarval durati

arrow sense herishell weigh

tability (h2%) foion  

itability (h2%) foht  

or

or

rrow sense heritapupation ra

ability (h2%) foate  

or

ment length

itative traitss ace

Table-15 : Evaluation index (EI) of the thirteen quantitative traits in four multivoltine breeds/race during three seasons and mean of three seasons

Quantitative

traits Breeds / race

Fecundity Hatching

Weight of single

V instar larva

Larval duration

Cocoon yield / 10,000 larvae

brushed Cocoon weight

Shell weight

Shell ratio

Pupation rate

Filament length Denier Renditta Sum

Average EI

By Number

By weight

Pre-

mon

soon

se

ason

MU1 56.09 60.58 54.94 55.99 53.83 45.68 56.80 55.50 54.47 50.00 55.70 40.00 54.10 693.68 53.36 MU11 57.17 54.00 56.58 55.77 48.46 61.90 58.40 59.00 58.37 52.15 56.15 50.00 59.10 727.05 55.93 MU303 53.94 42.80 55.88 55.55 42.83 54.31 54.40 54.50 54.31 37.63 55.47 39.00 53.50 654.12 50.31 PM 32.79 51.81 32.73 32.67 62.64 29.09 30.80 31.50 32.93 62.41 32.68 70.00 33.00 535.05 41.16

Mon

soon

se

ason

MU1 56.26 52.13 59.62 55.58 52.01 56.57 55.19 55.00 54.06 52.06 55.13 50 56.95 710.56 54.65 MU11 57.05 56.95 66.17 56.85 50.73 56.93 56.15 55.88 54.68 55.43 55.13 53.45 56.44 731.84 56.21 MU303 53.89 49.86 59.02 55.19 38.62 54.01 53.75 54.41 54.24 41.96 54.73 45.10 49.49 664.27 51.10 PM 32.80 62.78 34.62 32.36 62.63 33.57 35.10 34.70 34.33 58.70 35.00 53.44 35.99 546.02 42.00

Post-

mon

soon

se

ason

MU1 57.03 63.69 55.83 55.75 48.89 53.91 54.08 54.80 54.20 56.50 56.20 43.33 56.86 711.07 54.70 MU11 57.82 55.73 55.83 57.40 43.84 59.46 58.59 58.40 55.97 55.40 55.85 43.33 58.68 716.30 55.10 MU303 55.04 45.13 55.65 54.09 42.69 53.78 54.65 54.00 53.07 40.70 55.27 36.66 50.84 651.57 50.12 PM 33.11 40.92 32.67 32.80 66.56 33.23 32.96 32.40 36.81 59.75 32.69 63.33 38.33 535.56 41.20

Mea

ns o

f thr

ee

seas

ons

MU1 56.46 58.80 56.77 55.80 51.58 52.05 55.09 55.10 54.24 52.85 54.65 44.44 55.97 703.80 54.14 MU11 57.35 55.56 60.05 56.15 47.68 59.43 57.71 57.76 56.34 53.99 55.71 48.93 58.06 724.72 55.74 MU303 54.29 45.93 56.33 55.46 41.37 54.03 54.27 54.30 53.87 41.09 55.16 40.25 51.28 657.63 50.59 PM 32.90 51.84 33.38 32.57 63.94 31.96 32.95 32.87 34.69 60.29 33.46 62.26 34.11 537.22 41.32

44

45

Table-16 : Evaluation index (EI) of the thirteen quantitative traits in four bivoltine breeds/race during three seasons and mean of three seasons

Quantitative

traits Breeds / race

Fecundity Hatching

Weight of single

V instar larva

Larval duration

Cocoon yield / 10,000 larvae

brushed Cocoon weight

Shell weight

Shell ratio

Pupation rate

Filament length Denier Renditta Sum

Average EI

By Number

By weight

Pre-

mon

soon

se

ason

MG408 57.74 62.46 50.77 57.20 59.07 51.60 51.78 50.52 50.96 56.17 50.78 31.82 52.47 683.34 52.56 MU854 52.95 56.36 48.92 54.58 57.06 50.47 47.22 48.48 48.35 55.46 49.38 59.09 47.40 675.72 51.98 CSR2 44.10 36.00 66.35 35.75 33.64 64.51 66.44 63.91 67.30 35.88 66.05 50.00 64.02 693.95 53.38 NB4D2 52.95 50.68 45.12 55.46 50.23 46.55 45.55 43.61 45.37 57.57 47.79 63.63 46.92 651.43 50.11

Mon

soon

se

ason

MG408 67.21 64.41 50.21 53.82 57.15 57.78 51.61. 50.65 50.89 63.19 53.44 61.11 55.43 736.90 56.68 MU854 58.43 58.22 44.34 52.55 55.23 54.57 46.92 47.24 48.83 58.90 48.19 58.89 54.63 686.94 52.84 CSR2 59.18 59.31 67.31 33.42 32.88 62.09 67.18 66.76 65.84 45.01 63.94 58.89 63.67 745.82 57.37 NB4D2 59.18 59.35 43.25 60.20 56.72 49.55 44.39 47.35 49.46 50.90 46.52 57.41 46.21 670.49 51.58

Post

-mon

soon

se

ason

MG408 57.76 50.61 50.82 57.06 64.35 51.14 50.86 50.00 50.09 55.81 57.61 57.69 52.56 706.36 54.33 MU854 55.43 50.82 49.83 57.06 56.11 50.28 48.72 46.00 48.06 55.72 51.75 55.30 51.75 676.83 52.06 CSR2 54.99 56.76 67.00 34.87 36.11 66.00 67.25 67.00 66.50 35.68 60.01 44.61 64.90 717.68 55.20 NB4D2 41.32 62.80 47.39 62.99 56.43 49.43 46.16 41.50 46.39 55.81 42.61 57.69 48.46 658.98 50.67

Mea

ns o

f th

ree

seas

ons MG408 55.91 61.31 50.47 54.08 60.16 52.02 50.77 52.69 56.72 52.93 55.33 51.36 53.72 707.67 54.70

MU854 49.24 53.24 45.19 53.61 58.77 50.30 50.11 51.53 49.41 57.37 52.18 56.45 50.03 677.63 52.05 CSR2 48.59 55.41 67.01 35.77 33.46 56.87 67.12 65.76 61.79 35.74 66.52 55.45 64.87 715.36 55.29 NB4D2 53.28 59.95 43.33 59.49 52.42 48.80 50.29 46.00 47.15 54.20 48.96 55.45 39.33 658.70 50.67

0

10

20

30

40

50

60E

I

0

10

20

30

40

50

60

70

EI

M

0

10

20

30

40

50

60

70

EI

Mu

Fig. 28

Fig. 30: E

Fig. 32 : E

Fig. 28-f

Multivoltines    

ultivoltines

ultivoltines           

8: Evaluation in

Evaluation inde

Evaluation index

-33 : Evaluatifour multivol

              Bivoltine

Bivoltin

          Bivoltines

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46

ion Index (EIltine and four

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Fig. 33: Eval

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Fig. 34f

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47

tion Index (Eltine and four

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Discussion

Discussion The lepidopteran member, mulberry silkworm B. mori, is one of the important

beneficial insect known for the production of silk. Several quantitative traits in this

organism which are of paramount importance to industry are known to be controlled

either by polygenes and/or by major genes and the degree of manifestation of these

traits is greatly influenced by the environment. In a pioneering attempt Kogure (1933)

underlined the importance of environmental factors with reference to light and

temperature on the expression of the economic traits in some temperate silkworm

races. Later several attempts were made to understand the differential response of

different strains of silkworm B.mori to the changing environmental conditions.

(Nagatomo, 1942; Matsumura & Takeuchi, 1950; Suzuki, 1954; Morohoshi, 1957 ,

1969; Fakuda et al., 1963; Sidhu et al., 1969 and Kashiviswanathan et al., 1970,

Samson & Sudharkaran, 1974). Thus, the breeders have taken cognescence of variable

expression of the quantitative traits in order to achieve maximum selection gain either

among the pure stocks in a germplasm bank or hybrids in a breeding programme.

Allard and Bradshaw (1964) in their investigations utilizing endemic plant species

demonstrated that the performance of a plant species in a given environment will be

the best choice of its suitability during breeding programme.

In the present investigation, an evaluation of the potentialities of the three

evolved multivoltines and Pure Mysore race and four bivoltines are undertaken by

rearing them in three different seasons of the year. The data observed during three

seasons are statistically analyzed utilizing analysis of variance to understand seasonal

performance. The rearing data was subjected for analyzing inbreeding coefficient,

narrow sense heritability and multiple trait evaluation indices. The results of seasonal

performance and three evaluation parameters namely inbreeding coefficient, narrow

sense heritability and multiple trait evaluation indices are discussed in this chapter.

The data analysed for thirteen economic traits namely, fecundity, hatching

percentage, weight of single fifth instar larva (g), larval duration (h), yield/10,000

larvae brushed by number, yield/10,000 larvae brushed by weight (kg), cocoon weight

(g), shell weight (g), shell ratio (%), pupation rate (%), filament length (m), denier (d)

and renditta (kg) which are recorded in three seasons are tabulated in Tables 2-5.

48

Perusal of the clearly demonstrates that the multivoltine breeds MU1, MU11 and

MU303 exhibits higher fecundity compared to Pure Mysore race. Similar observation

has been made by Narayanan et al., 1967; Sengupta 1969; Kashiviswanathan et al.,

1970; Subramanya 1985 and Raje Urs 1988; who have demonstrated that evolved

multivoltines lays higher number of eggs than Pure Mysore due to their parentage and

breeding programme adopted during hybridization and selection programme. Further,

all the four multivoltines exhibited higher fecundity during monsoon season followed

by post monsoon and pre monsoon period. Added to these Ueda et al (1969)

demonstrated that increased pupal weight helps in increase of fecundity. Decrease in

fecundity in all the breeds during pre-monsoon corroborates the findings of Tazima

(1958) who indicated summer months of tropics are not congenial for the expression

of this trait resulting in low fecundity and higher percentage of unfertilized eggs.

Similarly, higher hatching percentage observed during monsoon and pre-monsoon

season clearly indicates the influence of environmental factors on the expression of

this trait. The present result corroborate with the studies related to hatching

percentage in multivoltine silkworms that monsoon season is most favourable season

for the trait hatchability compared to summer season because cool and humid

condition during egg laying influences fecundity in any race (Sengupta,1969 and

Sengupta et al., 1971).

Analysis of the larval duration of the four multivoltines it is clear that the

improved multivoltines exhibited shorter larval duration during pre-monsoon season

than Pure Mysore race which has revealed longest larval duration of 643.00 ±12.247

hours. This can be ascribed to the fact that during continuous process of selection and

breeding over a period of time the improved multivoltines have acquired shorter larval

duration. Further, during summer months the larval duration is significantly lesser

than winter months. This has relevance to the findings of Yokoyama (1962),

Morohoshi (1969) who have demonstrated faster rate of development during summer

than winter months due to high metabolic activity observed in the larvae during

summer months. Contrary to the above findings, Narayanan et al., (1967),

Kashiviswanathan (1970), Yokoyama (1976), and Lekuthai (1972) demonstrated that

high density of larval populations and leaf quality greatly influences the larval

duration.

49

A close scrutiny of the data for the traits yield by number and yield by weight

in the four multivoltines clearly demonstrates that in Pure Mysore the trait yield by

number shows higher values, whereas the improved breeds recorded significantly

higher yield by weight than those of Pure Mysore. The higher effective rate of rearing

by Pure Mysore clearly indicates the adaptability of Pure Mysore race to local

conditions. Significant differences were noticed for the traits cocoon weight (g), shell

weight (g) and shell ratio (%) between improved multivoltines and Pure Mysore race.

Similarly, Sidhu et al. (1969) and Narasimhanna (1976) observed significant

differences in the cocoon weight (g), shell weight (g) and shell ratio (%) between

improved multivoltines AP series and Pure Mysore. In a similar study Rao et al.

(2006), have shown that higher values for these traits in the improved multivoltines

compared to Pure Mysore and Nistari race. The influence of season on the expression

of these productive traits is very distinct wherein, during summer months the cocoon

weight is less, shell weight is lower and pupal weight is higher resulting in lower shell

ratio (%) in all the breeds. In a detailed investigations, Sidhu et al. (1969) and Gamo

et al.(1976) reported that there is a negative correlation observed for the traits of

pupal weight and shell weight.

Regarding the character pupation rate percentage, Pure Mysore recorded

highest values compared to the evolved multivoltine breeds. Tazima (1958) reported

that Pure Mysore is known for its sturdiness is superior for the pupation rate

irrespective of seasons. The robustness of Pure Mysore race in different

environmental conditions has also been well documented by Subramanya (1985).The

declining trend for this trait in the multivoltines during pre-monsoon season can be

ascribed to the unfavorable environmental conditions prevailing during summer.

Similarly Narasimhanna (1976) recorded lower effective rate of rearing (ERR) for

multivoltine lines ‘AP’ series during pre-monsoon season. Similarly, Suresh Kumar,

et al. (1999) demonstrated adverse effects of environment on the expression of these

traits in silkworm breeds. The trait filament length altogether revealed a different

picture wherein, though Pure Mysore race recorded lower filament length yet, the

improved multivoltines recorded uniform higher filament length in all the seasons of

the year. Gamo et al. (1976) and Narasimhanna (1976) reported a very low impact of

environmental factors on the expression of this trait. It is important to observe the

finer denier in Pure Mysore and also in the University breeds which denotes

superiority of the new breeds.

50

The comparative analysis of the thirteen commercial characters clearly

demonstrates that MU1 exhibited a general trend of its superiority for two traits, MU11

for eight traits, and Pure Mysore for three traits in all the three seasons of the year.

The results revealed that the evolved multivoltines are superior for higher productivity

traits. Such studies were made by Sengupta, (1969), Sidhu et al. (1969), Sengupta et

al. (1971), Krishnaswami & Tikoo, (1971), Narasimhanna, (1976), Subramanya,

(1985) and Chanadrashekaraiah, ( 1992).

A comparative analysis of the data in regard to the four bivoltines (MG408,

MU854 , CSR2 and NB4D2) clearly demonstrated that the two evolved bivoltine breeds

of Mysore University MG408 and MU854 excelled over CSR2 for three important traits

namely hatching percentage, yield by number and pupation rate percentage thereby

indicating the suitability of these two breeds in the tropical environmental conditions.

A similar observation in regard to the evolved breeds MG405, MU406, MG414 and

MU281 for the viability traits over popular bivoltine breeds/race has been reported by

Subramanya et al. 1988 and Ramesh, 1996.

The superiority of the bivoltine breed CSR2 noticed by several workers is well

documented (Yamamoto 1995; Basavaraja et al., 1995; Kamble, 1998; Datta et al.,

2000a; Nirmal Kumar et al., 2002; Krishna Prasad et al., 2003; Sudhakara Rao et al.,

2004b; Rayar, 2009) Contrary to this the superiority of NB4D2 race for viability traits

is also well documented (Benchamin & Krishnaswami, 1981b; Jolly, 1983;

Datta,1984; Ramesh et al.,1996; Maribashetty & Sreerama Reddy,1988 and

Umashankar, 2004). Further, from the foregoing discussions on bivoltines it is

indicative that the productivity traits like yield by number, yield by weight, cocoon

weight, shell weight shell ratio (%) as well as filament length are higher during the

monsoon period. The two evolved bivoltine breeds of Mysore University are distinct

with higher viability traits.

When once a race or a breed is maintained in a known environmental

conditions and or variable environmental conditions the genetic expression of the trait

bound to vary because of the gene environmental interactions, parentage of the

population and the consequence accumulation of genes for lowering the fitness of a

known trait. It is at this juncture systematic biometrical procedures are adopted by

51

animal breeders including the silkworm breeders. One of the prime procedures

developed is the application of the biostatistical procedure developed by Falconer,

(1989) to estimate the level of inbreeding which is inbreeding coefficient and is

denoted as ∆F. The importance of estimation of ∆F is very much essential to analyze

the level of inbreeding depression in the germplasm maintenance center. They have

repeatedly proved that sometimes the selection in a population to decide upon the

selection gain interferes with the constellation of the genes and genotypes resulting in

inbreeding depression. The purpose of the present study is to understand the silkworm

populations maintained in the germplasm stocks of the department though regularly

maintained through selection have accumulated any inbreeding coefficient (∆F) in

question. Swanepoel, (2007) demonstrated in South American sheep that the level of

inbreeding in any animal breeding programme need to be accounted for during the

selection process before utilizing them either in the cross breeding or race evolving

programmes. Hence, the purpose of this study is to analyze the ∆F to quantify the

actual level of inbreeding by systematically maintaining them for six generations by

analyzing seven economic traits.

The data in Table-10 clearly demonstrates the rearing performance and

inbreeding coefficient pertaining to three evolved Mysore University multivoltine

breeds along with popular Pure Mysore race pooled for six rearings during three

seasons. Utilizing linear regression model, ∆F was calculated following the procedure

of Subramanya and Stephen Bishop (2009). Several reports demonstrated that linear

regression method is important to estimate inbreeding depression for productive traits

in livestock breeding (Allaire & Henderson.1965; Henderson, 1984; Hudson & Van

Vleck, 1984; Wall et al., 2005). In cricket gryllus firmus it is reported that inbreeding

depression can cause substantial decrease in trait values and life history traits show

significantly higher inbreeding depression than morphological traits (Roff, 1998). In

mulberry silkworm, majority of the reports for the expression of traits relates to the

correlation of quantitative traits (Nacheva et al., 2001 and Nagaraju, 2002).

Correlation between yield and biochemical parameters in mulberry silkworm was

reported by Chatterjee et al. (1993). The studies on inbreeding in silkworm have been

attempted by Petkov et al. (1999). The calculated ∆F values in both evolved breeds

and in Pure Mysore race clearly indicated a higher standard error over the mean ∆F

values for all the traits studied thereby indicating that the selected populations have

52

maintained the consistent values and insignificant inbreeding depression due to the

continuous selection. In many instances the ∆F values are nearer to the standard error

in traits such as cocoon weight and shell weight. However, in the present investigation

the standard errors are large for all the traits understudy demonstrating the lack of

inbreeding depression. Falconer (1989), demonstrated that the absence of inbreeding

depression in any population is a clear indication of little dominance variation. The

present study clearly indicates that the inbred stocks are maintained systematically

through selection during the course of time and space.

In regard to bivoltine breeds a similar trend was observed wherein the mean

values of the quantitative traits are on the higher side than the multivoltines. In these

breeds/race, the ∆F values are almost nearer to the standard error of cocoon weight,

whereas for other traits it is always on the higher side. The ∆F values ranges from a

lowest of 0.001 (cocoon weight) to a highest of 0.482 for larval duration. A similar

observation in the inbred populations of livestock animals were reported where in the

minimum selection of herds will result in consistent ∆F values for the selected traits

(Swanepoel et al., 2007; Barczak et al., 2009). The pie graphs shown in Fig 14-20

clearly indicate that ∆F is consistent for the traits analyzed.

Tables 12-13 clearly demonstrates the data pertaining to heritability in regard

to the GCV%, PCV%, narrow sense percentage and genetic gain at 5% level in four

multivoltines and four bivoltines in three seasons and overall results in Table-14.

The heritability determines the degree of resemblance between relatives and

therefore of great importance in breeding programmes (Falconer, 1989). The narrow

sense heritability (h2) is the ratio between additive genetic variations to the total

phenotypic variance and hence it is of high practical significance. The general trend

observed in any breeding programme between narrow sense heritability (h2) and

broad sense heritability (h2) clearly demonstrated that the narrow sense heritability

values are smaller than the broad sense heritability. Hence, Lynch and Walsh (1988)

considered the broad sense heritability as of more theoretical interest than practical

importance. Considering the importance of narrow sense heritability as the quickest

means to understand gene environmental interactions, additive and non- additive

genetic effects as well to understand the dominance effect of genes in selected

53

population of the germplasm stocks the present research work on heritability was

undertaken based on the study for six consecutive generations in different seasons of

the year.

The data in the Tables 12-13 clearly indicates that in the four multivoltines

the lowest h2 values was observed for larval duration (6.50) and pupation rate (6.98),

whereas the highest h2 values were observed for the trait filament length (41-58%).

The other traits namely larval weight, cocoon weight, shell weight and shell ratio (%)

revealed intermediary values between these two. Similarly, though the h2 values are

higher in bivoltines the trend observed for the economic traits is similar to those of

multivoltines. Perusal of literature clearly indicates that the magnitude of heritability

depends on the quantitative traits and low heritability implies the predominant effects

of the environmental factors (Lynch and Walsh, 1988).

Wherever h2 value is low it implies that the environmental factor greatly

influences that trait (Gamo & Hirabayashi, 1983; Singh et al., 1994; for pupation rate,

Seizo & Hideo, 1957, 1958; Yan, 1983; for larval duration, Giridhar et al., 1995; for

both larval duration and effective rate of rearing). Wherever higher degree of

heritability is seen it shows that these traits are not amenable for environmental

impact. (Giridhar et al., 1995; for shell weight, cocoon weight and filament length)

For instance the traits larval trait, cocoon weight, shell weight as well as filament

length recorded h2 values > 31 and < 61 and author opines that it is very difficult to

unravel the genetic and environmental interactions involved in the expression of these

traits. However, based on the results on h2 for the trait filament length it is possible to

say that this trait is controlled by large portion of additive genes there by indicating

that the effect of environmental factor is very low for the expression of this trait. The

present results for these four traits revealing higher heritability tally’s with the

findings of Gamo & Hirabayashi (1983), Rayar (1987), Ashoka & Govindan (1990b),

Banuprakash et al. (1999), Bhargava et al. (1992 & 1993), Giridhar et al. (1995),

Kumar et al. (1995), Kumareshan et al. (2007) and Kamrul et al. (2010) who have

indicated non-significant environmental influence on the expression of cocoon traits

and filament length character.

54

Estimation of h2 for the trait pupation rate clearly demonstrates that the

heritability ranges from 6.98-7.81% in multivoltines and 8.44-9.19 % in bivoltines.

The locally adopted multivoltine pure Mysore recorded lowest h2 value of 6.98%

among multivoltines and NB4D2 recorded lowest h2 value of 8.44% in bivoltine group.

The low heritability of Pure Mysore clearly indicates the superiority of this race for

pupation rate because of its adaptation to local environment since a long time.

Similarly among bivoltines low heritability value recorded for the breed NB4D2

followed by MG408, MU854 and CSR2.Our results are in agreement with the hypothesis

that traits closely associated with fitness would have lower heritability than the one

belonging to other categories (Falconer, 1989).

From Table-14 it is clearly evident that h2 value for the two traits larval

duration and pupation rate percentage is lowest in all breeds and it is in conformity

with the statement of Falconer (1989) who stated that such important character as

viability is always shown to have low heritability. Thus, the author is of the opinion

that though this trait is genetically controlled the environment plays a predominant

role for the expression of the traits. The finding of the present author supports the

above results wherein ‘h2’ values are lowest in pre monsoon season and highest in

monsoon season in all the breeds. In a pioneer findings Kobayashi et al. (1968)

working on the bivoltine races of European, Japanese and Chinese origin have shown

that survival rate always records low h2 values in these races as it is greatly influenced

by environmental factors (Ashoka & Govindan, 1990b; Giridhar et al., 1995;

Kumareshan et al., 2007 and Tribhuvan Singh et al., 2012). However, the heritability

estimates along with the genetic gain is usually more useful than heritability values

alone in predicting the resultant effect from selecting the best individuals.

The present study also brings to light a few contrasting results in regard to

values the h2 and genetic advance (GA). Hence, the overall picture that emerges out

from heritability values clearly distinguishes four categories of estimates of

heritability in relation to the genetic advancement as detailed below.

High heritability and high genetic advance: Under this category it is

noteworthy that the traits filament length and cocoon weight implying the response of

the quantitative trait to the phenotypic selection indicating the importance of additive

55

gene effects and phenotypic stability. (Rayar, 1987; Rayar et al., 1988; Rayar &

Govindan, 1990; Ashoka & Govindan, 1990b). The high heritability and high genetic

gain are the indication of additive gene effect. (Panse, 1957).The second category is

high heritability and low genetic advance. This association signifies how the traits

falling under this category respond better to hybridization and recurrent selection. In

the present study, the traits of larval weight and shell weight fall under this category.

These results suggest limited scope for manipulation of these traits due to non-

additive gene action and the present results on high heritability and low genetic

advance corroborates with the findings of Kamrul Ahsan et al., 2010. In the third

category, where both heritability and genetic advance values are lower which is

represented by the traits pupation rate and larval duration clearly demonstrates the

role of environmental factors in the expression of this trait as reported by Kumareshan

et al. 2007. The fourth category includes moderate heritability and lower genetic

advance values for the trait shell ratio which respond better to mass selection

corroborates with the studies of Ashoka and Govindan, 1990b and Kumareshan et al.,

2007). Such variable expression of heritability in relevance to genetic advance has

been estimated in plant species having high relevance to agriculture (Yu et al., 1993;

Masilamani et al., 2000; Anbessa et al., 2006; Mallikarjunappa et al., 2008;

Okwuagwu et al., 2008; Deb & Khaleque, 2009 and Rita et al., 2012). They have

highlighted the relation between the heritability and genetic advance in the germplasm

stocks to maintain the uniformity of a plant variety.

The rearing data calculated for thirteen quantitative traits were analyzed

during three seasons using the multiple trait evaluation index (EI) method revealed

differential EI values for each one of the traits when data is pooled. Among

multivoltines all the three breeds MU1 M11 and MU303 revealed a respective EI value

of 54.14, 55.74 and 50.59 compared to 41.32 in Pure Mysore race (Table -16). Among

the four bivoltines all the four scored >50 EI, CSR2 topped the list (55.29) followed

by MG408, MU854 and NB4D2 in the descending order. It is clearly indicative that three

multivoltines and four bivoltines stood within five ranks and can be used in the future

hybridization programmes. Utilization of EI methods to identify potential pure races

and hybrids is remained as powerful tool in adjudicating promising parental races and

hybrids (Krishnaswami et al., 1964; Singh & Subba rao, 1993; Sudhakara Rao et al.,

2001; Ramesh Babu et al., 2002; Rao et al., 2006 and Ramesh et al., 2008). This

56

method was utilized to understand heterosis and genetic distance in silkworm B. mori

(Talebi & Subramanya 2009). One noteworthy feature of the present study clearly

indicated that the Pure Mysore race recorded < 50 EI values for productivity traits

except for the traits hatching percentage, yield by number, pupation rate and denier

irrespective of the seasons which has revealed >50 EI values. This corroborates with

the findings of Talebi and Subramanya (2009) which is clear indication that Pure

Mysore still can be used in the hybridization programmes for improving viability

traits. The foregoing discussion based on the results clearly demonstrates that the

evolved multivoltines MU1, MU11 and MU303 exhibited superior performances over

multivoltine Pure Mysore, whereas the two bivoltines MG408, MU854, has revealed the

excellent viability traits similar to NB4D2 and better over CSR2. However the hybrids

with heterotic effects for commercial significance can be recommended only after

evaluating heterosis and superdominance utilizing all the multivoltine and bivoltines

mentioned above in different combinations. Hence in the subsequent two chapters the

author has undertaken a detailed study on these aspects to shortlist superior hybrids.

57

Summary

Summary 1. Three multivoltine breeds MU1, MU11, MU303 and Pure Mysore race along with

four bivoltine breeds MG408, MU854, CSR2 and NB4D2 were analysed for

thirteen quantitative traits by rearing them in three seasons of the year namely

pre-monsoon (March-June), monsoon (July-October), and post-monsoon

(November- February).

2. On the basis of the performance of multivoltines and bivoltines during three

seasons, it is found that the evolved multivoltine breeds MU1, MU11, MU303are

superior to Pure Mysore race for productivity traits, The assessment of

economic traits of the breeds MG408, MU854, CSR2 along with NB4D2 race

clearly demonstrates that CSR2 breed excelled over all the other three breeds for

the traits of fifth instar larval weight, yield by weight, cocoon weight, shell

weight, shell ratio, filament length and recorded lower values for renditta.

NB4D2 race recorded superiority for the traits larval duration by exhibiting

shortest larval duration and finer denier, whereas MG408 and MU854 for the four

traits namely fecundity, hatching percentage, yield by number and pupation rate

percentage. The higher survival values of the MG408 confer an additional

advantage of rearing them in tropical climates.

3. A comparative study on the seasonal effect in the expression of quantitative

traits it is clear that both multivoltines and bivoltines exhibited superior

performance during monsoon season followed by post-monsoon and pre-

monsoon season. Thus, it is opined that the genes governing the quantitative

traits exhibited differential response to different environmental conditions.

4. Inbreeding coefficient (∆F) was estimated in the multivoltine and bivoltine

breeds/race for seven quantitative traits namely weight of single fifth instar

larva, larval duration, cocoon weight, shell weight, shell ratio (%), pupation rate

and filament length for six generations. The results have shown that all the traits

exhibited positive non-significant ∆F values by their higher standard error

indicating the absence of inbreeding depression. The results also imply that

because of clonal selection at every generation for various quantitative traits the

inbreeding depression was not observed.

5. The narrow sense heritability (h2) estimation (pooled for all the three seasons)

both in the multivoltine and bivoltine breeds/race clearly demonstrated that the

58

59

heritability values are < 10% for larval duration and pupation rate percentage,

between 10% -30% for shell ratio (%), between 30%-50% for shell weight and

remaining three traits namely V instar larval weight, cocoon weight and filament

length exhibited h2 values between 50%-62%. The h2 value also varies in

different seasons. The low h2 value of <10 and high genetic advance value of

<50 demonstrates the importance of environmental factors on the expression of

this trait and the high h2 value and genetic advance (>50) for three traits indicate

the role of additive gene effects. The results utilizing the eight breeds/race in the

present experiment clearly recorded differential expression of heritability for

different traits in relevance to the calculated genetic advance thereby indicating

the eight breeds/race have uniform genetic constitutions of their own and can be

further utilized in the hybridization programme.

6. Based on evaluation index values it is clear that MU1, MU11and MU303

revealed respective EI values of 54.14, 55.74 and 50.59 compared to 41.32 in

Pure Mysore. Similarly, all the four bivoltines recorded >50 EI values. The

higher EI values clearly indicate their importance in the hybridization

programme.