Embed Size (px)
Citation preview
UNIVERSITI PUTRA MALAYSIA
TRANSMISSION AND PATTERN OF SPREAD OF CHILLI VEINAL MOTTLE VIRUS BY APHIS GOSSYPII
GLOVER (HOMOPTERA: APHIDIDAE)
LEE KUE MOl
FSAS 1992 4
TRANSMISSION AND PATTERN OF SPREAD OF CHILLI VEINAL MOTILE VIRUS BY APHIS GOSSYPII
GL OVER (H OMOPTERA: APHIDIDAE)
By
LEE KUE MOl
Thesis Submitted in Fulfihnent of the ReqUirements for the Master of Science
in the Faculty of Science and Environmental Studies
Universiti Pertanian Malaysia
1992
ACKNOWLEDGEMENT
The author wishes to thank in particular her supervisor, Associate
Professor Dr. Norani A bdul Samad, Department' of Bioch emish'y and
Microbiology, UPM, and co-supervisors Associate Professor Dr. Mohd
Yusof Hussein, Department of Plant Protection, UPM, and Dr. Inon
Sulaiman, Department of Plant Protection, UPM, for their supervision
and advice throughout the duration of the project.
Appreciations are also extended to Dr. Rajan Amartalingam,
Department of Agronomy and Horticulture, UPM for identification of
weed species, Prof. S. Iyama, Department of Agronomy and Horticulture,
UPM, Endk Mohd Said Saad, Lecturer, Department of Agronomy and
Horticulture, UPM for their advice on statistical analysis, Ms Lai Khiok
Moi for translating the abstract, and staff of UPM Electron Microscopy
Unit, for their kind assistance and cooperation and Cik Armi Shamsuar
for taking the pains and extra hours typing the manuscript.
The author also wishes to thank MA RDI for supplying chilli seeds.
Financial assistance from Universiti Pertanian Malaysia and IRPA Research
Grants is gratefully acknowledged.
The author wishes to thank Ms Chin Chiew Lan, Mr. Lam Chin
Hee, Cik Esah Munji and Ms Low Kwee Choon for their support and
encouragement throughout the studies.
The author owes a great deal to her family and beloved husband
Lok Yok Fong for their love, patience, understanding and encouragement.
ii
TABLE OF CONTENTS
Page
ACKN'OWLEDGEMENT .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii
LIST OF TABLES .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi
LIST OF FIGURES .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viii
LIST OF PLATES .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . x
LIST OF ABBREVIATIONS .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi
A BSTRA CT .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xii
ABSTRAK ..................................................................................... xiv
CHAPTER
1
2
3
INTRODUCTION .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . LITERATURE REVIEW .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..
1
3
Non-Persistent Chilli (Capsicum annuum) Viruses .............. .................. . .. ...... .......... 3
Chilli Viruses in Malaysia ...................... . .. . . . . . . . . . . 3
Transmission of Plant Viruses by Aphids .. ....... 4
Spread of Non-Persistent Viruses by Aphids ....... ...................................................... . 5
Host Range of Viruses and Vectors .................... 6
GENERAL MATERIALS AND METHODS .. . . . 8
Virus Isolate ... .......... .. .. .................. . . ... .................. 8
Aphid Culture .............. ......................................... 8
Test Plant ................................ ......... ..................... .. 9
4 VECTOR FORMS AND AQUISITION PERIOD 10
Introduction .............. ................................. ........ ... 10
iii
5
6
Page
Materials and Methods .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... . . . 10
Results and Discussion .. . .. . . . . . . .... . . . . . . . . . . . . . . . . . ... . . . . . 11
Effects <;>f �phid' s Form on CVMV TransmISSIon .... . . . . . . .. . . . . .. . . . . . . .... . . .. . ... . . . . . . . . . . . . . . . . . . . . . 11
Effects <;>f �cquisition Period on CVMV TransmIssIon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Relationship between Vector Forms and Acquisi�io!, Feeding Period in CVMV TransmIssIon .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
PERSISTENCY AND RETENTION OF CVMV INFECTIVITY BY A. gossypii . . . . . . . . . . . . . . . . . 16
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Materials and Methods .... . . . . . . . . . . . . .... . . . . . . . . . . . . . . . . . . . . 16
Retention and Persistency of Infectivity as Determined by Serial Transfer . . . . . . . . . . . . . . . . . . . . . . . 16
Retention and Persistency of Infectivity as Determined by Post-acquisition Starvation .... . . ......... . . ....... . ... ........ .. . ... . . . . . . . . .. .. . . . .... . . 17
Results and Discussion ... .. .. . . . . . . .. . . . .. . . ... . . . . . . .. . . . . . . . 17
Retention and Persistency of Infectivity as Determined by Serial Transfer . . . . . . . . . . . . . . . . . . . . . . . 17
Retention and Persistency of Infectivity as Determined by Post-acquisition Starvation . . . . .. . . . . . . . ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
PATTERN OF SPREAD .. . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Introduction .. . . . . . . . ... . . . . . . . . . . . . . . . . . . . ... . . . . . . . . ... . . . . . . . . . . . . . 28
Materials and Methods ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Results and Discussion .. . . . . . ... . . . . . . . . . . . ...... .... .. . ..... . 32
Aphid Infestation .. . . . . . . . ... . . ..... . . ... . ... .. . . . . .... ... . .. . . . . . 32
iv
7
8
9
10
Page
Virus Spread ............... ..................... ..... . . . . ... . . . . . . . . . . 39
Association between Virus Spread and Distribution of Vector '" . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
Effects of Aphid's Form and Initial Inoculum Location on CVMV Transmission .... 49
WEED SPECIES AS HOST OF CVMV .. . . . . . . . . . . . . 52
Introduction ......... . ....... .... . . ...... ... . . . ....... ... ........ . . . .. 52
Materials and Methods ............. . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
Results and Discussion ........... . ......... ............. . ..... 53
TRANSMISSION OF CVMV BY NON-COLONISING APHID SPECIES . . . . . . . . . . ... . . . . . . . . . . . 65
Introduction ............. ................ .......... ...... ...... . ... . .. 65
Materials and Methods .......... . ............................. 65
Results and Discussion ........................................ 66
GENERAL DISCUSSION .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. CONCLUSIONS .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
68
73
REFERENCES .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . .. . . . . . . . .. . . . . 75
APPENDICES.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . .. . . . . . . . . . . . . . . . . . . . 83
VITAE .......... .................................................................................. 89
v
Table 1
2
3
4
5
6
7
8
9
10
11
12
LIST OF TAB LES
Percentaf: o f CVMV Infected Plants b y Different orphological Forms and Different Acquisition Feeding Time of A. gossypii ................... A nalysis o f Variance (Vector Forms and AcquIsition Period) ... . . . . . . . , ......... . .. ......... . .... ................. Percentage Transmission of CVMV by Single
�ig�:;;�!e�!t��� .. ����.�.�.��.�.�.����.�.�.�.� .......... Percentafe Transmission of CVMV b y a G rouv 0 5 A. gossypi i Throu�h S e ria l Trans er a t 1 0 Minutes Interva with 15 Minutes Acquisition Feeding . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . .
Percentafe Transmission of CVMV b y a Group 0 10 A. Gossypii Throuyh Serial Transfer a t 1 0 Minutes Interva with 1 5 Minutes Acquisition Feeding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Percentaxe Transmission of CVMV by a S i n g l e . gossypii with 1 5 Seconds A cquis i t ion F e e d i� a t Various Post -acquisition Starvation Ime . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Percentaxe Transmission of CVMV b y a S ing le . gossypii with 1 5 Minu tes A cquis i t ion F e e d i¥t at Various Post -acquisition Starvation Ime . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . .
Variance Mean Ratio (VMR) Analysis and K-Values of Aphid Infested Plants Per Day . . . . . . . . . . . . . . . . .
Variance Mean Ratio (VMR) Analysis and K-Values of CVMV Spread Per Week . . . . . . . . . . . . . . . . . . . . . . . . . . .
Percenta6"e of CVMV Infected Plants Without any AphId Infestation for Treatment A, B, C and D ...................................... .................... ................... Host Range of Chilli Veinal Mottle Virus . . . . . . . . . . . . . . . . .
Comparison of Vector Efficiency of Aphid Vectors in Transmission of CVMV .. . . . . . . . . . . . . . . . . . . . . . . . . . .
VI
Pag e
12
13
18
20
21·
24
25
38
47
48
54
66
Table Page
13 Percen tare Transmission of CVMV by a Group 0 5 A. gossypii with 1 5 Minu tes A cquIs i t ion Feed i� a t Vari ous Pos t-
84 acquisition Starvation Ime ........................................ 14 Percen tape Transmission of CVMV by a
Groul? 0 1 0 A. gossypii with 1 5 Minutes A cquis i tion F e e d iti at Var ious Pos t -acquisition Starvation Ime . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
15 Analysis of Variance (Patterns of Spread) . . . . . . . . . . . . . . . . 86
16 Percentage of Virus Incidence for Morpholo-gical Form in Pattern of Spread Experiment . . . . . . . . . . . 87
17 Percentage of Virus Incidence for Different
!r��r��T�����r���\�� .. �����.���.�.�.�.���.��� .......... 88
vii
LIST OF FIGURES
Figure Page
1 Percentage of CVMV Transmission for 1, 5 and 10 A . gossypi i p e r P lant i n S er ia l
22 Transfer ..........................................................................
2 P ercenta�e of CVMV Transmission with Post-a�qUlsition Starvation for 1, 5 and 10 A.
26 gOSSyp ll . .......................................................................... 3 Zoning Pattern (Zone 1, 2, 3 and 4)
(i) Treatment A and B (ii) Treatment C and D Shaded square (_) indicates initial source of inoculum. <1 Indicates healthy plant ....................... 30
4 G raphic Rehresen ta tion of the Rate o f Infestation: t e Number of Plant Colonised b y A . gossypi i. Each shaded s quare �II) r e p r e s e n ts a n aphid in fe s ted p la n t (Trea tment A - A p terous adul ts , in i t ia l inoculum at the centre) ...................... ........... .............. 33
5 Graphic R�resentation of the Rate of Infesta-tion: the umber of Plant Colonised by A. gossYT! ii. Each shaded s(¥are (_) reGresents an a8hid infested plant reatment - Alate adu ts, initial inoculum at the centre) ...................... 34
6 Graphic R�resentation of the Rate of Infesta-tion: the umber of Plant Colonised by A. gossypii. Each shaded square (_) represents an aphid infe s ted plant (Treatment C -Apterous adults, initial inoculum at the corner) ............................................................................ 35
7 Graphic representation of the rate of Infesta-tion: the number of II ant colonised by A. gossypii. Each shade sc;are (_) rebresents an f:hid infested plant reatment - Alate adu ls, initial inoculum at the corner) ....................... 36
8 �ll�:�r�a�e��: �:.��������.���.�.�����.��.��� .......... 37
viii
Figure Page
9 Pattern of Spread of CVMV for Apterous A. f!ssypii Released on Infected Plants in the entre (Treatment A). Each Shaded Square
(.) Represents an Infected Plant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
10 Pattern o f Spread of CVMV for Alate A . goss�t!/i Released on the Infected Plants in the entre (Treatment B). Each Shad ed Square (.) Represents an Infected Plant . . . . . . . . . . . . . . . . . . . 41
11 Pattern of Spread of CVMV for Aiterous A. goss�ii Released on the Infecte Plants in the entre (Treatment C). Each Shaded Square (II) Represents an Infected Plant . . . . . . .. . . . . . . . . . . . 42
12 Pattern of Spread of CVMV for Alate A . gossY6ii Released on the Infected Plants in the entre (Treatment D) . Each Shad ed Square (_) Represents an Infected Plant ................... 43
13 Effect of Distance from Source Plant (zone 1 = 7 cm, zone 2 = 14 cm, zone 3 = 21 cm and zone 4 = 28 cm) on Percentage of Proportion of CVMV Infected Plant �er Zone (zone 1 = 12 plants, zone 2 = 20 fa ants, zone 3 = 28 plants and zone 4 = 36 p ants) . . . . . .. . . . . . . . . . . . . . . . . .. . . . ... . . . . . 44
14 CVMV Progress Curves for Ala te and Apterous A. goss�ii with Initial Inoculum at the centre and orner (Treatment A, B, C and D for all the 3 replicates) ...................................... 46
15 Weekly Rate of Spread of CVMV by Alate and
�f�����:<!::��fi� .. ���.�.��.����� .. ���.����.�.�� .......... 50
ix
Plate
1
2
3
4
5
LIST OF PLATES
C. annuum var MC4 Systemically Infected wi th CVMV Showing Dark Mottl i n g , Malformation a�d Stunting . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . .
C. annuum var Ca l i fornia Won d e r Systemically Infected with CVMV Showing Stunting, Malformation, Blistering and Mosaic .. . . . .
Datu ra m e te l ( Solanaceae) Systemical ly Infected with CVMV Showing Blistering, Mottling and Malformation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Infected Heliotropium indicllm (Boraginaceae) A. Leaves from Infected Plant B. Infected Plant - Right Healthy Plant - Left . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cleome ru tidosperm a (Cal'paridaceae) Systemi-cally Infected with CVMV Showing Mottling . . . . . . . . .
x
Page
59
60
61
62
63
LIST OF ABBREVIATIONS
AzMV Arizona Mosaic Virus
CBRSV Cabbage Black Ring Spot Virus
CMV Cucumber Mosaic Virus
CVMV Chilli Veinal Mottle Virus
PeMV Pepper Mottle 'virus
PMMV Pepper Mild Mottle Virus
PMoV Pea Mosaic Virus
PLRV Potato Leaf-roll Virus
PRPMV Puerto Rico Pepper Mosaic Virus
PVMV Pepper Veinal Mottle Virus
PVY Potato Virus Y
SBM · Sugar Beet Mosaic
TEV Tobacco Etch Virus
TsEV Tobacco severe Etch Virus
YvSB Yellow virus infected Sugar Beet
min minutes
sec seconds
xi
Abstract of thesis rresented to the Senate of Universiti Pertanian Malaysia in fulfillment 0 the requirements for the degree of Master of Science
TR ANSMIS SION AND PATTERN OF S PRE A D OF CHILLI V EIN A L M OTTL E VIRUS BY APHIS GOSSYPII
GL OVER (H OMOPTERA: APHIDID AE)
by
LEE KUE MOl
June 1992
Supervisor: Associate Professor Norani Abdul Samad, Ph. D.
Faculty Science and Environmental Studies
Chilli veinal mottle virus (CVMV) is a serious problem and h as
become a m ajor limiting factor in growing and production of chilli in
M al aysi a. This virus is transmitted non-persistently by aphid, Aphis
gossypii. CVMV control efforts h ave been unsuccessful due to l ack of
knowledge on the epidemiology of the virus.
S tudies on tr ansmission and spre ad of CVMV to chilli using
nymphs and adults of A. gossypii were conducted in the l aboratory and
glasshouse . Aphids and test plants (Capsicum annuum cv. Me 4) were
cultured and maintained in insect proof glasshouse.
Fifteen seconds and thirty seconds acquisition feeding time were
found to be the optimum time for A. gossypii to transmit CVMV. All
aphid forms were equally efficient in CVMV transmission.
xu
A single A. gossyp i i was able to transmit and retain CVMV
regardless whether it was fed or starved. A. gossypii lost CVMV infectivity
more rapidly in serial transfer (when feeding) than in post-acquisition
starvation (when starving). Transmission level decreased as the period of
serial transfer (0 - 60 min) and post-acquisition starvation time (1-120 min)
increased, however, the l evel of transmission increased with aphid
density.
Colony establishment of A. gossypii was faster when aphids were
initially released on healthy plants than on CVMV infected plants.
Apterous vectors spread CVMV more efficiently than alate vectors .
However, CVMV s pread faster when A. gossypii was placed on the
inoculum source. Apterous adults released near the inoculum source
achieved the highest �evel of transmission compared with the alates. In the
beginning, CVMV spread occurred mostly near the inoculum source and
moved outward thereafter.
Weeds species infected by CVMV included members of family
Amaranthaceae, Boraginaceae, Compositae and Solanaceae. CVMV failed
to infect plant species from the family Acanthaceae, Capparidaceae,
Chenopodiaceae, Convulvulaceae, Labiatae, Leguminosae, Malvaceae,
Onagraceae, Portulaceae, Rubiaceae, Scrophulariaceae and Sterculiaceae.
Amongst the non-colonising aphids, Aphis craccivora, was found to
be the most efficient in transmitting CVMV followed by Hys teneura
setariae, Rhopalosiphum maid is, Lipaphis erysimi and Toxoptera all1'alltii.
xiii
Abstrak tesis yang dikem�kakan kepada Senat Universiti Pertanian Malaysia sel)agal memenuhi syarat-syarat untuk Ijazah Master Sains
TRANSMISI DAN CORAK PENYEBARAN CHILLI VEINAL MOTTLE VIRUS OLEH APHIS GOssypn
GLOVER (H OMOPTERA: APHIDIDAE)
oleh
LEE KUE MOl
Jun 1992
Penyelia: Profesor Madya Norani Abdul Samad , Ph. D.
Fakulti: Sains dan Pengajian Alam Sekitar
Chilli veinal mottle virus (CVMV) merupakan satu masalah yang
serius dan m e n jadi satu faktor penghad d alam penanaman d an
pengeluaran ciIi di Malaysia. Virus itu ditransmit secara tidak kekal oleh
kutu daun, A. gossypii. Usaha-usaha untuk mengawal CVMV belum lagi
berjaya kerana kekurangan pengetahuan mengenai epidemiologi virus
tersebut.
Kajian penjangkitan dan penyebaran CVMV kepada ciIi telah
d ijalankan di dalam makmal dan rumah kaca dengan menggunakan
peringkat nimfa dan dewasa A. gossypii. Kutu daun dan tanaman kajian
(Capsicum al1l1uum cv. MC4) telah dikultur dan dipelihara di dalam rumah
kaca.
Keputusan kajian menunjukkan masa pemerolehan optimum
untuk A. gossypii mentransmit CVMV adalah 15 saat dan 30 saat. Semua
peringkat kutu daun adalah sarna cekap di dalam transmisi CVMV.
xiv
A. gossypii tunggal berkeupayaan menyebar dan mengekalkan
CVMV samada i a diberi makan atau dilaparkan. A. gossypii hHang
kejangkitan CVMV lebih cepat dalam pemindahan bersiri (semasa makan)
berbanding dengan kelaparan selepas pemerolehan (semasa dilaparkan).
Tahap transmisi berkurangan dengan penambahan tempoh pemindahan
bersiri (0-60 minit) dan masa kelaparan selepas memperolehan (0-120
minit), begitupun, paras kejangkitan bertambah dengan kepadatan kutu
daun.
Perkembangan koloni A. gossypii adalah lebih cepat apabila kutu
daun dilepaskan ke atas pokok yang sihat berbanding dengan pokok yang
dijangkiti CVMV. Penyebaran CVMV oleh vektor tidak berkepak adalah
l ebih berkesan berb anding d engan vektor yang berkepak. Wal au
bagaimanapun, penyebaran CVMV adalah lebih cepat apabila A. gossypi;
diletakkan di atas sumber inokulum. Tahap transmisi tertinggi diperolehi
dari kutu daun dewasa tidak berkepak yang dilepaskan berhampiran
dengan sumber inokulum berbanding dengan kutu daun berkepak. Pada
mulanya, CVMV disebarkan berdekatan dengan sumber inokulum dan
kemudiannya merebak ke arah Iuar.
Spesies rumpai yang dijangkiti CVMV termasuk ahli-ahli dari
famili Amaranthaceae, Boraginaceae, Compositae dan Solanaceae. CVMV
didapati gagal menjangkiti spesies dari famHi Acanthaceae, Capparidaceae,
Chenopodiaceae, Convulvulaceae, Labiatae, Leguminosae, Malvaceae,
Onagraceae, Portulaceae, Rubiaceae, Scrophulariaceae dan Sterculiaceae.
xv
Kutu -kutu daun tak berkoloni , Aphis craccivora didapati paling
cekap d alam penyebaran C VMV, diikut i o leh Hys teneura setariae,
Rhop alosip hum maidis, Lip aphis erysimi dan Toxoptera aura ntii.
xvi
CHAPTERl
INTRODUCTION
Chilli or Cayenne pepper (Capsicum annuum L.), is a lowland crop
grown throughout Peninsular Malaysia. Johore , Perak and Kelantan have
frequently been reported to have higher acreage compared to other states
(Anon, 1986). The acreage of C. annuum in 1979 was 913 hectares and in
1986 was approximately 1200 hectares . The obvious increase in Clcreage
indicates a high demand for chilli from year to year. The total acreage of
this crop is still small , although Malaysia's climate is favourable for the
growing of chilli and despite the high ex-farm price of the commodity. As
such, Malaysia's import of chilli has exceeded 25 million ringgit annually
(Anon, 1987).
One of the major problems limiting the production of chilli is the
high incidence of virus infection which could reached 100% when the crop
reached maturity (Abdul Samad , 1984). A survey conducted by Fujisawa
et al. (1986) reported that 80% of the cult ivated chill i crops manifested
infection by mosaic virus diseases in the field in Peninsular Malaysia.
The virus disease showing mosaic symptom in C. annuum was first
described by Ong (1975) and named it as CVMV. CVMV belongs to
potyvirus group with particles ranging from 750 to 900 mn and produces
the characteris t ic p inwheel inclusions in th in sections of leaf t issues
(Abdul Samad, 1986). CVMV is transmitted by aphids in a non-persistent
manner. Chemical control for vectors of non-persistent viruses had been
ineffective because these viruses could be transmitted during brief acquisi
tion and inoculation feeding, while insecticidal action comparatively takes
1
2
a longer period to kill the aphid vectors (Broadbent, 1956; Ribbands, 1964;
Gonzalex and Rawlins, 1969; Smith et al., 1969; Zitter and Simon, 1980) .
Informations on the epidemiology, in particular transmission, virus
vector relationship, epidemiology, host range and symptomatology of
CVMV and its vectors are still incomplete and badly needed to develop
new strategies for CVMV management.
The objectives of this research were:
1. To s tudy the efficiency of different forms of A. gossypii with
different acquisition period in transmitting CVMV.
2. To determine the influence of acquisition time and density of
A. gossypii on the retention and persistency of CVMV while
feeding (serial transfer) and when starving (post-acquisition
starvation).
3. To determine the pattern of spread of CVMV as related to A.
gossypii colonisation.
4. To investigate the possibility of CVMV transmission from
common weed species found in chilli growing areas.
5. To determine the ability of other non-colonising aphids in
transmitting CVMV.
CHAPTER 2 LITERATURE REVIEW
Non-persistent Chilli (Capsicum annuum) Viruses
Non-persistent viru s es, also known as s tylet-borne or non
circulative viruses, are the most common type of viruses transmitted by
aphids and causing great losses to crops (Bradley, 1964). These viruses can
be acquired and transmitted during probing of less than 60 sec (Swenson,
1969; Harris, 1977; Markham et ai., 1987).
The non-persistent viruses of chilli reported in Malaysia are chilli
veinal mottle virus (CVMV) and cucumber mosaic virus (CMV) (Fujisawa
et ai., 1 986) . Other non-persistent viruses of chilli which belong to the
potyvirus group have also been reported in Florida (Simon,1956; Zitter,
1971, 1972, 1973; Pieczarka and Zitter, 1981), India (Raychaudhuri, 1969),
Israel ( Cohen and Marco, 1 973), Ari zona (Nelson and Wheeler, 1972),
Nigeria (Lana et al., 1975), North Carolina (Lapp and Gooding, 1976) and
Texas (Mclean, 1962). Seth and Dhanraj (1972) also reported other groups
of viruses on chilli in India. The tobamovirus in Sicily, Italy (Wetter et nl., 1984) and pepper yellow vein virus are some of the other more recent
viruses reported on chilli (Fletcher et ai., 1987).
Chilli Viruses in Malaysia
In Malaysia a mosaic disease on chilli was first described by Ong
(1975) and named it chilli veinal mottle virus (CVMV). The virus belongs
to the potyvirus group with particles ranging from 750 - 900 nm and
produces the characteristic pinwheel inclusions (Abdul Sam ad, 1986). The
3
4
CVMV could be transmitted'in a non-persistent manner by several aphid
species, namely A. craccivora (Koch), A. gossypii (Glover), A. spiraceola
(Patch), Myzus pers icae (Sulz), Toxoptera citricidus (Kirk), Hys tel'Olleura
setariae (Thos) and Rhopalosiphum maidis (Fitch) (Ong, 1975). The disease is
endemic, affecting C. annuum and C. fru tescens grown in Peninsular
Malaysia (Abdul Samad, 1984) . CVMV produces a symptomatic mosaic on
the leaves and causes stunting of the plants. Yield could be markedly
reduced if the plants were infected at an early stage of growth. Other
viruses namely tomato spotted wilt virus (TSWV) (Abdul Sam ad, 1986),
cucumber mosaic virus (CMV) and tobacco mosaic virus (TMV)(Fujisawa
et al., 1986) had also been reported to infect chilli.
Transmission of Plant Viruses by Aphids
Worldwide, it has been estimated that more than half of the plant
viruses are transmitted by aphids (Eastop, 1977), where both the viruses
and aphid vectors are found on crops and weeds (Bos, 1981). In Malaysia
and other parts of the world where chilli is grown, chilli viruses are
frequently transmitted by aphids. M. persicae and A. gossypii are the two
aphid species which have been reported to be the vectors frequently
transmitting non-persistent viruses (Eastop, 1977).
The process of virus transmission covers uptake, carry over and
inocula tion of the virus ( S torey, 1 9 3 9; Bradley, 1 964) . Success of
transmission depends on several factors (Eastop, 1977) which directly or
indirectly influence the process of transmission. Amongst thes e, the
abiotic factors (eg. environmental condition) may affect vector's behaviour
which in turn may affect transmission efficiency (Pirone and Harris, 1977;
5
Harris, 1983). For example, abiotic factors such as light intensity, exposure
time and temperature had been found to influence aphid's behaviour
(Cook and Sylvester, 1964; Sylvester and Richardson , 1966;Wyatt and
Brown, 1977; Kemp and Troup, 1978). On the other hand, the biotic factors
such as v ector distribution and v ec tor-plant interaction play ed an
important role in virus transmission (Gill, 1 970; Zitter, 1977; Zitter and
S imons, 1 980; Raccah, 1 986; Markham et al. , 1 987), whil e virus titre
affected virus transmission. Watson and Plumb (1972) and Altieri (1981)
reported that very low virus titre would decrease uptake and carry over
resulting in an unsuccessful transmission of the virus.
Spread of Non-Persistent Viruses by Aphids
Three conditions, namely the presence of a vector, a sufficient level
of inoculum and mobility of vector must be fulfilled before a virus could
be spread (Broadbent, 1956; Irwin and Ruesinks, 1986). The interrelation
ship of these three conditions will then determine the level of the spread
(Broadbent, 1956).
The source of inoculum is of prime importance in virus spread . For
instance, the spread may be faster if the source of inoculum is near the
target crops as compared to a more distant source of inoculum (Garrett
and Mcl ean, 1 983) . The tim e of onset of the initial inoculum is also
important in spreading the virus (Thresh, 1986). The vector has a greater
chance of acquiring the virus if the onset of initial inoculum occurs in the
early part of the crop growth period. The age of the infected plants in the
entire crop may also determine the severity and spread of the disease;
younger plants not only serve as a source of infection but they are more
6
susceptible and may become stunted while infection on older plants may
cause less damage to the crop (Conroy, 1965; Sievert, 1971; Eastop, 1977;
Rose, 1978; Ong et al., 1980; Francki, 1984).
The presence of vectors, especially migrant alate vectors coming
from outside a crop provides the initial spread of the virus, whereas the
nymphs and apterous vectors are later responsible for the secondary
spread within the crop (Taylor, 1986) . Muniyappa (1983) and Sigvald
(1986) showed that the time of migrant aphid entering the crop correlated
stronger with virus spread than with the aphid numbers.
Host Range of Viruses and Vectors
Infected weeds and other wild plants which thrive near the crops
are important sources of inoculum during the primary spread of the virus
(Thresh, 1978) . Crop plants other than chilli also b ecome the host of the
vectors. These plants are important for survival, spread, establishment of
the virus as well as being the refuge for the vectors (Bos, 1981). Therefore,
i t is important to know the host range of vectors and the virus for the
development of effective control measures.
Plants of the families such as Solanaceae, Compositae, Chenopodia
ceae and Convolvulaceae have been reported to be hosts of chilli viruses
in Malaysia and elsewhere. Natural infection on weeds (eg. Datura ferox,
Physalis mendocina) by CMV, PVY and TMV had also been reported in
Mandoza, Argentina (Feldman and Gracia, 1972). This is anticipated since
most aphid pests spend part of the time colonising wild plants or weeds
which in some instances became alternative hosts of the virus (Eastop, 1981) .
7
Most aphids have a restricted range of host plants. However,
eleven species of aphids have been reported to be polyphagous; namely
Aphis citricola, A. craccivora, A. fabia, A. gossypii, AulacortllUm circumflexllm,
A. solani, Macrrosiphum euphorbia, Myzus persicae and Toxoptera aurantii
(Eastop, 1981). Amongst these M. persicae, A. gossypii and A. cracci'llora
have been reported to be the maip vectors of CVMV in Malaysia (Ong,
1975).
CHAPTER 3
GENERAL MATERIALS AND METHODS
Virus Isolate
An isolate of CVMV was collected from infected C. fl1111l111m in the
field at Universiti Pertanian Malaysia, Serdang, Selangor, Malaysia. The
virus was propagated in chilli plants by mechanical inoculation at two
leaf stage and maintained in an insect-proof glasshouse. The leaves that
developed mosaic symptoms were used as virus sources.
Aphid Culture
Colonies of A. gossypii were started from a single apterous adult
aphid collected in the field. The aphids were continuously reared on C.
annuum cv. MC4 in an insect-proof cage mad e of nylon m esh ( 1444
mesh/ cm2) in a glasshouse. The colonies were transferred fortnightly to
fresh host plants to prevent accidental infection by viruliferous aphids
from outside and to ensure healthy condition of the aphids. Alate aphids
used in certain experiments were obtained from overcrowded colonies. To
ensure that the aphid colonies were virus free, transmission tests were
carried out from time to time.
Al l s ix s tages of A. gossypii were us ed in al l the exp erim ents,
namely 1st, 2nd, 3rd and 4th nymphal ins tars and apterous and alate adult
forms, unless otherwise stated.
B
