Breeding Sorghum

Presented byNIRANJAN KUMAR CHAURASIA

DEPT. OF PLANT BREEDING AND GENETICSASSAM AGRICULTURAL UNIVERSITY,JORHAT

2015-AMJ-155

Grain Sorghum: Sorghum bicolour L Moench ( 2n=20)

Order: PoalesFamily: PoaceaeSubfamily: PanicoideaeTribe: Andropogoneae

USES OF SORGHUM

Used as human feed and fodderThe plant stem and foliage are used for

green chop, hay, silage, and pasture.The stem is used as building material,

and plant remains (after the head is harvested) may be used for fuel.

Cytological evidence suggested Sorghum evolved from the wild Arundinecea.

Snowden believed that the wild African Arundinacea : S. arundinacea, S. verticelliflorum and S. sudanese were the progenitors of cultivated crop

De Wet et al. (1976) derived from Aethiopicum and Verticelliflorum by selection mainly for tough racemes and larger panicles in the Ethiopia-Sudan region of Africa.

Africa is considered to be the place of origin of Sorghum

Origin

Its very difficult to determine when and where domestication began.

Murdock (1959) suggested that the Mande people around the headwater of Niger River may have domesticated sorghum

Doggett (1965) indicated that the practice of cereal domestication was introduced from Ethiopia to Egypt about 3000BC and it is possible that the sorghum domestication began at that time

Introgression studies indicate that cultivated sorghums probably developed through disruptive selection (Doggett 1965)

When and how sorghum spread from Africa is a matter of conjecture. Durra types today extend continuously from Ethiopia, along the Nile to the Near East, and across India to Thailand

The durra types were probably introduced to Arabia as early as the Sabian Empire (1000-800BC) and later spread to the Near East along the trade route

Sorghum probably reached India by both land and sea routes. Its cultivation in India is mentioned in legends that date back to the first century A.D. It is not a very old crop in India and its Sanskrit name is Yavanala means reed barley or reed grain suggesting that sorghum probably followed barley in India

Domestication

Classification Snowden’s Classification (1936) –most detailed, comprehensive and

is much in use

Divided the genus into two sections:

1. Eusorghum (smooth nodes) – Halepansia and Arundinasea

Halepansia has five species

Arundinasea contains two series Sponstanea and Sativa.

Sponstanea contains the wild grassy types grouped into 21 species and Sativa contains all the cultivated Sorghums falling into 31 species grouped into six subseries viz; Drummondii, Nervosa,

Bicolor, Guineensia, Caffra and Durra

2. Parasorghum (Bearded nodes)

Harlan’s and De wet Classification (1972)

5 basic races of S. Bicolor ssp bicolor cultivated races and ten hybrid races

Basic races1. Race bicolor2. Race guinea3. Race caudatum (C) 4. Race kafir (K)5. Race durra (D)

Characteristics of the basic races• Bicolor: Grain elongate, sometimes slightly

ovate, nearly symmetrical dorso-ventrally; glumes clasping the grain, which may be completely covered or exposed

• Caudatum: grain markedly asymmetrical, the side next to the lower glume flat or somewhat concave, the opposite side rounded and bulging; the persistent style often at the tip of a beak point pointing towards the lower glume; half the length of the grain or less

• Durra: grain rounded ovate, bulging and widest above the middle, wedge shaped at the base, glumes very wide; the tip of a different texture from the base and often with a transverse crease across the middle

• Guinea: Grain flattened dorsoventrally, sublenticular in outline, twisting at maturity nearly 90⁰ between gaping invoute glumes that are form nearly as long to longer than the grain

• Kafir: Grain approximately symmetrical, more or less spherical, not twisting, glumes clasping and variable in length

1. Bicolor 2. Caudatum 3. durra 4. Guinea 5. Kafir

Hybrid races

1. Race guinea-bicolor (GB)

2. Race caudatum-bicolor (CB)

3. Race durra-bicolor (DB)

4. Race guinea-caudaturr,(GC)

5. Race guinea-kafir (GK)

6. Race guinea-durra (GD)

7. Race kafir-caudatum(KC)

8. Race durra-caudatum(DC)

9. Race kafir-durra (KD)

10. Race Kafir-bicolor (KB)

The Classification is based on mature spikelets

The Gene Pool• Harlan & De Wet (1972), the cultivated

races (S. bicolor ssp bicolor) and their wild and weedy relatives (S. bicolor ssp arundinaceum) form the primary gene pool.

• The secondary gene pool consist of the S. halepense, miliaceum, Johnson grass and S. almum.

• The tertiary gene pool consist of the Saccharum, Sorghastrum and Miscanthus

• Grain type-Kharif and rabi• Fodder-Single cut and multicut• Sweet sorghum (bio fuel and fodder)

Classification based on Use

Botany• Sorghum is annual/ perennial

grass, the roots are adventitious and fibrous, stem is erect and made up of nodes and internodes, the pith may be sweet, juicy or dry. The leaves are 7 and 28 arranged alternating to opposite side with parallel venation. Presence of waxy layer limits the water loss. The panicle varies loose to compact, in some varieties panicle remain surrounded by sheath and some times penduncle recurred, giving pendent head referred as “goose neck”.

• Panicle consists of spikelets in pairs; the sessile is hermaphrodite and fertile while other pedicillate is sterile. The sessile spikelet consists of inner and outer glumes enclosing two flowers, upper one is perfect and lower one is reduced. The perfect flower has thin narrow hairy lemma and small pelia enclosing three stamen, two lodicules and bifurcated feathery (brush like) stigma. The pedicillate flower is without pelia and ovary.

Grain• Grain is caryopsis,

endosperm is starchy, and embryo consists of plumule, coleoptiles, radical coleorhizae referred as scutelum

Basic Characteristics

Adaptability • Sorghum adapts to many

environments, requiring 90 to 140 days to mature. Highest yields are usually obtained from varieties maturing in 100 to 120 days.

Water Relations • Sorghum is usually grown under hot, dry conditions. Compared to

maize, sorghum has a more extensive and fibrous root system. The plant roots penetrate a greater volume of soil to obtain moisture. Fertilizer, even under low rainfall conditions, encourages root development; hence the roots are able to extract moisture from a greater volume of soil.

• Sorghum requires less moisture for growth than some other cereal crops: studies show that sorghum requires 332 kg of water per kg of accumulated dry matter; maize requires 368 kg of water; barley, 434 kg; and wheat, 514 kg

• Sorghum tends to "hang on" during the dry period and resumes growth with the return of rain.

• The water requirement of sorghum increases as the plant grows, reaching a peak during the flowering period: after this time, the moisture consumption decreases.

Temperature Relations • Sorghum will make grain even when

temperatures are high. Crossing may be difficult if temperatures are 40⁰C or more, with relative humidity of 30% or less; but a crop can be obtained if moisture is available

• Floral development and seed set are normal at temperatures of 40 to 430C and at 15 to 30% relative humidity, if soil moisture is available. Sorghum is not as tolerant to cool weather

Floral biology and crossingThe flowering occurs prior to sunrise and extended up to mid- day, the blooming starts from tip of the panicle in downward direction. The stigma is receptive before flowering and remains receptive for 6 to 8 days.Pollens are viable for few hours and fertilization is completed with in 2 to 4 hours of pollinationJawar is normally self pollinated crop but stigmas exposed before dehisce lead to 6 to 30% cross pollination. The glumes open due to swelling of lodicules and another come out stigma. The stigma remains receptive for 8 to 16 days after blooming.

Emasculation & Pollination Hand Emasculation:• Only the part of the penduncle is emasculated. Flowered tips and

lower branches are removed by clipping. About 50 florets that would flower on next day are selected and emasculated and covered with suitable paper bag.

Hot Water Method: • In this method the sorghum head is immersed in water at 45 0 to

48 0C for 10 minutes, without injury to the stigma.Plastic Bag Emasculation: • In this method, sorghum panicle is covered with plastic bag.  This

creates high humidity inside the bag.  Under such a humidity, the florets open, the anthers emerge but shed no pollen.  The anthers are knocked free of head by tapping.  In this method, some selfing occurs.  Therefore, marker genes are needed to identify the plants arising form selfed seed. Pollination is done on next day between 9 to 10 a.m. all flower come to bloom. Inserting and shading the head in the bag collect the pollen. Another technique is clipping the heads early in the morning and placed in the boxes or flower pots kept in protected place. The collected pollens are dusted over exposed stigma or the pollen producing head and brushed over emasculated head.

Production Challenges

Stem borer Mold

Drought Striga

Anthracnose

Breeding Objective for seed sorghum• high yield (fertilizer responsive) • wide environmental adaptiveness • disease and insect resistance • nonlodging • appropriate time to maturity • good plants at reasonable population levels • good threshability • general attractiveness • height-about 1.25 to 2.0 metes • large head size good head exsertion• head not too compact or too grassy• head erect rather than recurved• good tillering, with heads on all culms maturing the same

time • good seed set• seed size and number

Breeding Procedures: Pure Line Selection: • 1) M-35-1, 2) Sel-3, 3) Yashda , 4) Maulee( RSLG-262).

Pedigree Method:  • SPV-86 ( R-24 X R-16), SPV-504 (Swati) (SPV 86 X M-35-1), CSV -15 R,

( SPV-475 X SPV-462)

Back Cross Breeding: • Disease and pest resistance and also CMS can be transferred• These conventional breeding methods, used as a short-term strategy

produce varieties with a relatively narrow genetic base, favor the accumulation of linkage blocks due to rapid fixation of genes, and limit recombination options because of continuous inbreeding

• Alternate Strategy – Population Improvement and Hybrid Breeding- recombination to break linkages between desired and undesired traits,- provides scope for increased utilization of biotic and abiotic stress resistant, but agronomically non-elite source germplasm lines. - provides long-term breeding strategy to derive diverse and broad genetic-based superior varieties/hybrid parents

Population Improvement

• Purpose: for improving a single trait; for selecting several traits simultaneously; for generating fertility restorer and non-

restorer (maintainer) populations for deriving hybrid parents

Steps: Selection of component parents introgression of a GMS gene, and random mating among parents.

Genetic male sterility genes, their designated symbols and mechanism of sterility in sorghum. Source: Adapted from Rooney (2000).

Gene symbol

Mechanism Reference

ms1 Normal pollen is dominant over aborted or empty pollen cells

Ayyangar and Ponnaiya (1937)

ms2 Normal pollen is dominant over aborted or empty pollen cells

Stephens (1937)

ms3 Normal pollen is dominant over aborted or empty pollen cells

Webster (1965)

ms4 Empty pollen cells Ayyangar (1942)ms5 Aborted pollen Barabas (1962)ms6 Micro-anthers without pollen Barabas (1962)ms7 Empty pollen cells Andrews and Webster

(1971)al Anther less stamens Karper and Stephens

(1936)

Population Improvement Methods in Sorghum

Mass Selection• Doggett (1972) has described modified mass selection with

alternating male sterile (female) and male-fertile (male) plants selection in successive generations,

• Aimed at enhancing selection response by increased parental control.

• In one cycle, seed is harvested from only selected male-sterile plants. These seeds are bulked and sown to constitute the population for the next cycle of selection, wherein, male-fertile plants are selected and harvested seed from selected plants is bulked for selection of male-sterile plants. This procedure is continued.

• Mass selection should be used in the first few cycles of selection after synthesis of a population.

• This makes populations reasonably uniform for plant height and maturity before using methods of recurrent selection requiring family/progeny evaluation.

Half-sib family/progeny selection.

• Requires two generations per cycle since it involves progeny testing• Male-sterile plants are tagged at the time of flowering and are allowed

for open-pollination• Each head is harvested and threshed separately. A part of the seeds

from each head is sown in yield trial (evaluation phase) and the remaining is saved as remnant seed

• The best entries are chosen from the yield trials, and the remnant seed from these entries is bulked to constitute the population for the recombination phase

• Along with the replicated yield trial of half-sib families a separate nursery is planted simultaneously to identify male-sterile plants

• Sib-mated male sterile heads are harvested and bulked with remnant seed of families selected on the basis of grain yield and other selection criteria as appropriate in a yield trial

• This bulk is sown to allow random mating in the next season • Again, male-sterile plants are tagged and harvested individually to

form the next cycle of evaluation • Recombination is carried out in the off-season and evaluation in the

main season.

Full-sib family/progeny selection Full-sib families can be developed by crossing selected

male-fertile plants onto selected male-sterile plants

The full-sib families so generated are evaluated in a yield trial and the remnant seed of the selected families is then bulked and allowed to recombine

Crosses of male-fertile plants with male-sterile plants are then made and the cycle repeats

In this scheme of selection, the unit of selection is full-sib families and the breeder has the control over both the parents unlike in half-sib family selection

S1 family/progeny selection• Most effective selection schemes for sorghum (Gardner 1972)• Heads of male-fertile plants are bagged at flowering to ensure

selfing, or they can be tagged to ensure that heads from male-fertile plants and not male-sterile plants are harvested at maturity. Selected plants are harvested and threshed separately, each head forming an S1 family. These families are evaluated in yield trials

• Remnant seed from the families selected or their sibbed families based on the yield trials is sown, and seed from male-sterile heads are selected to ensure recombination

• Seeds from male-sterile heads are then bulked and sown• Male-fertile heads of good plants are identified for testing to

begin next cycle• The units of selection and recombination are S1 progenies• The basic concept behind selfed progeny selection is to expose

deleterious recessive genes to facilitate their elimination during evaluation and to increase additive genetic variation

S2 family/progeny selection In this scheme of selection process, heads of selected

male-fertile plants are bagged at flowering to ensure selfing, or they can be tagged to ensure that heads from male-fertile plants and not male-sterile plants are harvested at maturity.

The S1 progenies are grown and plants in S1 progenies rows are selected and again selfed. Selected selfed plants are harvested and threshed separately, each head forming an S2 family

These S2 families are evaluated in yield trials and handled exactly in a manner similar to that in S1 progeny selection and thus selfed/inbred progenies constitute units of selection in both the methods

Advantages S2 progeny testing is expected to result in

maximum gain per cycle Additive genetic variance is maximized in S2

families; the families are sufficiently uniform to permit

precise evaluation; selection for different traits can be done in various

generations ranging from half-sib to S2 according to the nature of their inheritance

the lines evaluated are more homozygous and it is hence easier to extract pure lines.

evaluation is expected to improve the probability of deriving more vigorous inbred lines

Testcross family/progeny selection A number of male-fertile plants from the base

population are selected and selfed and simultaneously crossed to a broad based tester. The resultant testcross progenies are evaluated in a yield trial to identify promising families, the units of selection

The remnant seed of selected testcross progenies is bulked and sown and allowed for open pollination with male-sterile plants

Seeds from male-sterile heads are then bulked and sown

Male-fertile heads of good plants are identified for test crossing to begin next cycle

Inter-population improvement methods

Half-sib reciprocal recurrent selection

In this scheme of selection, each population provides a source material to advance/ improve and also serves as a tester for the other populationIndividual selected male-fertile plants in one population, designated as ‘A’ will be crossed to several random male-sterile plants of the other population designated as ‘B’. In a similar manner, several selected male-fertile plants of population ‘B’ are crossed onto several random male-sterile plants of population ‘A’The crosses thus generated are evaluated in a yield trial and seeds from selected male-fertile plants are bulked and grown in isolationIncorporate heterozygous male-sterile plants into these populations. Allow for random pollination of male-sterile heads. Harvest seed from male-sterile plants in each population and bulk to constitute the new populations from which male-fertile plants would be selected and crossed to male-sterile plants from the other population and the cycle repeats

Hybrids in Sorghum

Concept: Cytoplasmic Male Sterility system for Hybrid sorghum

History of sorghum breeding- the hunt for cytoplasmic male

sterilityThe hybrid vigor was first recognized in

sorghum by Karper and Corner, in 1927- produced by hand-emasculation

In 1948, researcher initiated studies to look for cytoplasmic male sterility as a method for commercial seed production in sorghum

Reciprocal crosses between Milo and Kafir produced first evidence that a male sterility inducing cytoplasm has been found (Stevens and Holland, 1954)

Hybrid Grain Sorghum Production (3 parent lines)

A-Line Male Sterile

B-Line Maintainer

X

A-LineMale Sterile

XR-LineRestorer

Hybrid

Identification B- and R-Lines• Hybrids are obtained by crossing

pollinators with a male sterile line• The test crosses are evaluated for the

sterility maintenance or fertility restoration in them through bagging test

• Bagging test- covering 4-6 panicles with paper bag before anthesis, and observing the seed set after two to three weeks

Evaluation of test crossReaction Conclusion Further usageTest cross exhibiting absolutely no seed set on all the bagged panicles

Mainter or B-line Source of a new A-line

Test cross with complete seed set on all the bagged panicles

Potential restorer or R-Line

Serve as male parents to produce hybrids

Testcross with a partial seed-set on all the bagged panicles

Serves neither as restorer nor as maintainers

Male parents are rejected

Testcrosses with full seed-set on some bagged panicles and no seed-set in others

Segregation for fertility- restoration or sterility- maintainer genes

Not pursued further

Sweet Sorghum

Similar to grain sorghumHas dual-purpose nature -grain and sugar-rich stalksPilot studies indicated ethanol production from sweet sorghum cost-effectiveHigh water-use efficiency, seed propagation, hybrid technology in placeCO2 neutralHigh positive energy balance (1:8)

Why Sweet Sorghum????

Breeding StrategyDevelopment ofa. Improved sweet sorghum varieties, hybrid parents and hybridsb. Improved bmr varieties, hybrid parents and hybridsc. Improved crop management practices

Public-Private-People Partnerships

Why Hybrids???

Heterosis for cane , grain and juice yields, and total sugar

More stable compared to varieties Early and predictable maturityEasy to schedule cane supplies

Brown midrib sources and improved lines

• bmr mutant sources: IS 21887 ( bmr 1), IS 21888 (bmr3), IS 21889 (bmr 6), IS 21890 (bmr 7) and IS 21891(bmr 8), IS 40602 (bmr 12)

• Sources used: bmr 1, bmr 3, bmr 7• Potential sources: bmr 6, bmr 12• Number of high biomass bmr B-lines - bmr

1: 2, bmr 3: 3, bmr 7: 6• Number of high biomass bmr R-lines - bmr

1: 10, bmr 3: 3, bmr 7: 9

Sorghum as Fodder

Quality Parameters• Crude protein (CP) or digestible crude protein

(DCP) and total digestible nutrients (TDN) which are measurable in synonymous terms as measures of dry matter digestibility (DMD) or digestible dry matter (DDM).

• Total soluble sugars (TSS), HCN, tannins, acid detergent fibre (ADF), neutral detergent fibre (NDF), sweetness (reducing sugars), in vitro dry matter digestibility (IVDMD), intake (cellulose digestibility after 24 and 48 hours of incubation), nutritive value index (NVI) and metabolizable energy (ME).

Breeding Objectivesdry matter yield leaf spot disease resistance shoot fly stem borer resistance seed setting abilityquality parameters/sweetness/intake low HCN/tanninshigh protein yield harvest index (digestibility/biological yield) single cut/double cut/triple cut

manageability

Interspecific hybrids

• Unlike sorghum, sorghum-sudangrass hybrids tiller profusely, produce succulent stems, have high leaf to stem ratio, re-grow quickly, withstand multi-cuts, and are low in HCN and tannins.

• Single and three-way interspecific hybrids have been developed

Sorghum Breeding in ICRISAT

• Sorghum improvement started in 1972• Breeding concepts and objectives and the mode

of research involving partners have undergone several changes since the initiation of sorghum improvement at ICRISAT and the evolution can be grouped into six major phases-

1. Wide adaptability and high grain yield (1972-1975)2. Wide adaptability and screening techniques (1976-

1979)3. Regional adaptation and resistance breeding (1980-

1984)4. Specific adaptation and resistance breeding (1985-

1989)5. Trait-based breeding and sustainable productivity

(1990-1994)6. Upstream research and intermediate products

(1995 onwards)

Wide adaptability and high grain yield (1972-1975)

This period was characterized by the generous support of development investors and an immediate need to develop varieties with wide adaptability and higher grain yield

Higher grain yield, primarily in the red grain background, was the major breeding objective.

Population improvement through recurrent selection was carried out in 33 populations collected from the USA (from the universities of Nebraska, Purdue and Kansas) and Australia, and from the programs in West Africa (Nigeria) and East Africa (Tanzania

Resistance to shoot fly, grain mold and Striga was considered important later on and programs to identify resistant sources were initiated. Studies on grain characters that contribute to food and nutritive traits such as high lysine content were also begun

Wide Adaptability and Screening Techniques (1976-1979)

The major research thrusts during this period were (a) identifying high-yielding genotypes; (b) developing efficient screening techniques for yield constraints; and (c) identifying sources of resistance

New variability was generated by crossing male-sterile plants in populations with select germplasm lines or named cultivars to select for high grain yield. Population breeding approaches

Greater emphasis was laid on breeding photoperiod-insensitive varieties with earliness. Screening techniques to identify sources of resistance to major pests and diseases (including Striga) were given major emphasis during this phase

While retaining the emphasis on population improvement, programs for wide adaptability, high grain yield and specific pedigree breeding were also initiated for (a) drought resistance; (b) stalk rot resistance and postrainy season adaptability; (c) downy mildew resistance; and (d) grain mold resistance in cream colored grain genotypes.

A major shift in selection from red-grained to white-grained genotypes occurred during this phase. Research on food grain quality was pursued with greater vigor.

Regional Adaptation and Resistance Breeding (1980-1984)

This phase was characterized by (a) intensive testing of varieties in international trials for high grain yield in various regions and in international nurseries for resistance to various pests and diseases; (b) initiation of work on regional adaptability including tolerance to early-, mid- and late-season drought; (c) breeding for high grain yield and resistance to various pests and diseases to ensure sustainability of production; (d) large-scale production and testing of hybrids; and (e) further refinement of various screening techniques for grain mold, downy mildew, rust, anthracnose, leaf blight, charcoal rot, shoot fly, stem borer, midge and Striga

techniques to screen materials for emergence under high temperatures and crusting, and for tolerance to early-, mid- or late-season drought were also developed

Collaborative research was initiated at various locations

Specific Adaptation and Resistance Breeding (1985-1989)

This period was characterized by regional network trials and development of high-yielding and pest/disease-resistant pure lines.

Concerted efforts were made to identify the major abiotic and biotic constraints in each region and a breeding program was initiated to develop multifactor-resistant (MFR) populations and targeted populations. As a result, there was a shift from developing high-yielding populations to MFR populations

Trait-based Breeding and Sustainable Productivity (1990-1994)

Population improvement was scaled down to gene pool development as it was not found to be as efficient as pedigree breeding in meeting short-term goals

Combining several resistance traits at one time is less efficient. Hence, a trait-based breeding approach was initiated

A participatory mode of research planning and execution was followed

an extensive program of diversifying and breeding new milo cytoplasmic male-sterile lines for earliness, introgression with Durra and Guinea races, incorporating bold and lustrous grain characters, and resistance to Striga, shoot fly, stem borer, midge, head bug, grain molds, downy mildew, anthracnose, leaf blight and rust was carried out

Novel populations or trait-specific gene pools for bold grain and high productive tillering were developed

Upstream Research and Intermediate Products (1995 Onwards)

emphasis was laid on upstream research including biotechnology tools emphasis is to produce parental lines (seed parents and pollen parents) and

gene pools. Accordingly, the objectives of the program are to breed resistant seed parents and restorer lines, to develop specific new gene pools and novel plant types and to identify and use molecular markers

Diversification of the genetic base of breeding lines is an important objective, which is achieved by intercrossing resistant sources of diverse origin – often of different races – with agronomically elite lines

At ICRISAT-Patancheru, recurrent selection is practised in broad-based, random-mating populations or gene pools for specific traits [such as maintainer (B), restorer (R), high tillering (HT), large grain (LG)]

In West and Central Africa (WCA), the development of random-mating populations of Guinea and Caudatum and another Guinea × Caudatum races has been completed

These populations will have good agronomic backgrounds and adaptability while preserving their broad genetic variability

Another important goal is to broaden the cytoplasmic-genetic diversity of hybrid parents.