Cotton leaf curl virus

History, symptoms,systematic position, mode of spread, Favourable condition,management

1. COTTON LEAF CURL VIRUS COURSE TEACHER Dr. PARTHASARATHY S Asst. Professor (Plant Pathology) STUDENT Miss. SRIMATHI P ID. NO. 2015021124 COLLEGE OF AGRICULTURAL TECHNOLOGY (Affiliated to Tamil Nadu Agricultural University, Coimbatore-3) Kullapuram (Po), ViaVaigai Dam, Theni-625 562

2. Cotton leaf curl virus Common Name : leaf curl disease of cotton International Common Names : cotton leaf crinkle; cotton leaf curl disease; leaf crinkle of cotton. Virus In Pakistan & North India - Cotton leaf curl virus . In India (South India) - Tobacco streak virus .

3. History & its significance First time cotton leaf curl disease was reported in Nigeria during 1912 ( Farquarson , 1912). Later on reported from Tanzania and Sudan in 1926 and 1934 respectively (Bailey, 1934). In Pakistan cotton leaf curl virus was reported for the first time in 1967 near Multan ( Hussain , 1975).

4. CLCuVD is passed on by its vector whitefly ( Bemisia tabaci ) and belongs to the genus Begomovirus family Geminiviridae ( Hameed et al. , 1994). Cotton Leaf Curl Virus Disease ( CLCuD ) is the most destructive disease causing huge losses to cotton production. (Khan and Ahmad, 2005).

5. There were intermittent reports of increase in disease spread mostly around Multan, Khanewal and Vehari which reached an epidemic proportion in 1993 with 8.9 lakh hectares that comprised about one-third of Pakistan’s cotton area under the severe grip of the virus. The production was 128 lakh bales in 1991-92 but declined to 79 lakh bales during the epidemic years in 1994-95 indicating 30-40% losses due to the disease. This epidemic was caused by the ‘Multan species CLCuMuV ’.

6. LRA 5166 as a resistant donor and cultivate the resistant varieties especially in hot-spot districts. There was a second outbreak in the Burewala area of Punjab province during the 2001-02 season and reduced the production to 100 lakh bales in the years 2002 and 2003. A new ‘ Burewala CLCuBuV species’ had infected all the varieties that were resistant to the ‘Multan CLCuMuV species’.

7. India experienced the leaf curl virus outbreaks in 1993 & 1996 just concurrent to the occurrence of epidemics in Pakistan during 1992 and 1995 . The leaf curl virus damage in India during the years 1998 to 2006 declined due to the cultivation of resistant varieties and intensive measures to control the whitefly and weeds. The complete replacement of varieties with new Bt cotton hybrids after 2007 changed the scenario .

8. By 2011, the area under Bt cotton hybrids reached more than 90% in Punjab and Haryana but was less than 70% in Rajasthan . It is probable that the slow rate of adoption of the new Bt -hybrids in Rajasthan resulted in low to moderate levels of disease incidence in the state.

9. SYMPTOMS Cotton Leaf Curl Disease ( CLCuD ) infected plants may show a range of symptoms depending on the severity of disease , Typical symptoms include thickening and yellowing of small veins on the lower surface of young leaves . Under severe attack of the disease, leaves curl downward or upward with stunted plant growth due to reduction of inter-nodal distance.

10. The severity of disease also produces a cup shape outgrowth on the lower side of the curled leaves that is known as Enation . The appearance of the disease at seedling stage seriously retards the flowering , boll formation, maturation , seed cotton yield and fiber quality. SYMPTOMS

11. © Padil Infected plant

12. © Intechopen (a) Healthy Leaf (b) Infected Leaf

13. ©Australian journal of crop science Leaf enation

14. SYSTEMATIC POSITION OF LEAF CURL VIRUS Domain: Virus     Unknown: "DNA viruses"         Unknown: “ ssDNA viruses"             Family: Geminiviridae                 Genus: Begomovirus                     Species: Cotton leaf curl virus

15. SYSTEMATIC POSITION OF TSV Domain: Virus     Unknown: "RNA viruses"         Unknown: "Positive sense ssRNA viruses"             Family: Bromoviridae                 Genus: Ilarvirus                     Species: Tobacco streak virus

16. MODE OF SPREAD Through vector - Bemisia tabaci   (White fly)  Whitefly ( B. tabaci ) is a member of order Hemiptera and family Aleyrodidae . Virus is transmitted in a persistent and circulative fashion. The virus is not transmitted transovarially by the vector .  B. tabaci feeds on phloem sap by inserting its stylets into plant tissue and locating the vascular tissue.

17. Whiteflies require an acquisition threshold period ranging from 15 min to 4 h and an inoculation threshold period of 5 min to 1 h to successfully transmit the virus. Upto 8 h latent period is also required between the acquisition and inoculation periods for successful transmission of the virus to new plants .

18. ©Cotton association of I ndia Whitefly - Adult

19. FAVOURABLE CONDITION Cotton leaf curl virus disease ( CLCuD ) is affected by climatic conditions like rainfall, wind and Temperature. Disease infestation increased in the range of maximum and minimum temperatures of 33-45°C and 25-30°C respectively.

20. Maximum disease incidence % was recorded at 6 week old seedlings and it gradually decreased with increase in age of the plant. Rainfall prior to seedling may result in development of an increased population of vector due to abundance in food source.

21. MANAGEMENT Adjust sowing time (mid April to mid May results in decrease of disease incidence). Increased plant spacing in the case of early sowing and decreased plant spacing under late sown conditions is effective in management of CLCuD . Destroy infected plants , especially after harvest. Crop rotation with crops that are not host plants for whiteflies.

22. Destruction of off- season weeds and clean cultivation during the season to minimise sources of virus inoculum . Avoid cultivation of malvaceous crops such as okra ( bhendi ) or tomato especially in disease prone areas. The applications of organic oils (canola, sunflower and cotton seed) were done at 25% concentration (25% oil and 75% vinegar) on young cotton plants in order to create hurdle against insect vector infestation.

23. Insecticides ( Imidacloprid ( Imidacloprid 25% WP), Megamos ( Acetamparid 20% SC and Bifenthrin ( Bifenthrin 10% EC)) were sprayed at their standard doses in the field for maximum mortality of whitefly with 7 days interval. Grow resistant varieties like XL1 , L1530 , X1730A , X 1030, B 6 L, RS - 875, RS - 810, RS - 2013, F 1861, L H- 2076, H-1117, H-1226 and hybrids LHH-144, CSHH198, CSHH238 and CSHH243.

24. TOBACCO STREAK VIRUS Cotton necrosis disease caused by tobacco streak virus (TSV) is an emerging threat in India ( Rageshwari et al ., 2016). Tobacco streak virus (TSV) was first identified in tobacco in Brazil (Johnson 1936; Costa 1945).

25. In Tamil Nadu, Nakkeeran (AICRP report 2010) first reported the association of TSV in cotton . DISTRIBUTION Tamil Nadu, Telangana , Andhra Pradesh and Maharashtra.

26. SYMPTOMS Initial symptom includes, (a) chlorotic lesions, which may later turn into necrotic, purplish brown spots, surrounded by yellow halos. The spots may be ( b,c,d ) chlorotic or necrotic, small or large, (e) purplish or purplish brown or brownish black, irregular or ( f,g ) ring-like, confined at the interlobular region /apex or distributed all over the lamina. In cases of severe infection, (h) drying of squares, stems and stunting of plants were also observed.

27. © www.researchgate.net/publication/320507097

28. MODE OF SPREAD Through vector – Thrips ( Thrips tabaci ) TSV is transmitted by infected pollen from alternate hosts and the only know mechanism of insect transmission is ingress of the virus from the pollen through wounds made by the action of thrips feeding on the leaf. The thrips do not transmit the virus directly through feeding, as with most other insect-vectored viruses.

29. FAVOURABLE CONDITION Minimum temperature (22.81°C), relative humidity (81.42%), and leaf wetness (23.94 h). MANAGEMENT Remove plant debris after harvest or any plant material that may serve as a source of inoculum . Keeping fields free of weeds is a good control strategy. Spinosad is generally more effective against thrips . One common form of management for viruses is to plant a desirable host for thrips around the cropping system. The thrips will insert their stylet and “clean” off any virus on their stylet before moving to the target crop.

30. REFERENCES https://www.icac.org/tis/regional_networks/asian_network/meeting_5/documents/papers/papmongad.pdf https://www.plantwise.org/KnowledgeBank/Datasheet.aspx?dsid=16813 https://www.ncbi.nlm.nih.gov/pubmed/11137169 https://www.sciencedirect.com/science/article/pii/S0168170200001957 https://www.cabi.org/isc/datasheet/16813 https://agrihunt.com