RANGASWAMY, K. T.GURUDEVI, V. NAVALI2020-10-032020-10-032018-09-24Th-12185https://krishikosh.egranth.ac.in/handle/1/5810152259Tobacco leaf curl virus disease (TbLCVD) is one of the important viral diseases of tobacco. Survey of six major tobacco growing areas of the state was carried out to record the incidence of TbLCVD and to collect the virus isolates for the identification of viruses associated with the disease. Survey revealed occurrence of the disease in the range between 12.54 to 38.95 and 17.03 to 35.85 per cent during 2016-17 and 2017-18, respectively. The highest incidence of the disease recorded in Shivamogga district (31.81 %) followed by Belagavi district (24.88 %). Phylogenetic analysis of the complete genome sequence of the TbLCV-MYS, TbLCV-MAN, TbLCV-CHN, TbLCV-SHG, TbLCV-DVG and TbLCVBEL isolates revealed the association of five distinct begomoviruses viz., Tomato leaf curl Karnataka virus (ToLCKV), Tomato leaf curl Kerala virus (ToLCV-K5), Tobacco leaf curl Yunnan virus (TbLCYV-Y143), Sri Lankan cassava mosaic virus (SLCMV) and Chilli leaf curl Multan virus (CLCMV). TbLCV-MYS and TbLCV-DVG clustered with ToLCKV, TbLCV-BEL clustered with ToLCV-K5, TbLCV-CHN clustered with TbLCYV-Y143, whereas TbLCV-SHG and TbLCV-MAN clustered with the CLCMV and SLCMV, respectively. The transmission characters were determined for TbLCV-SMG and TbLCV-MAN isolates by using whitefly (Bemisia tabaci) with 12 h each of acquisition access period and inoculation access period. Minimum of ten adult whiteflies were required to transmit 100 per cent disease. All the six isolates were successfully transmitted to tobacco, tomato, chilli, datura, goat weed, sunflower, sesamum and milk weed by using whiteflies but TbLCV-MAN and TbLCV-SHG isolates closely related to CLCMV and SLCMV, respectively were able infect jatropha and cassava which were not infected by other four isolates. Nine Nicotiana species evaluated against TbLCV, N. stocktoni and N. rapanda showed resistant reaction. Four different SSR markers (PT52937, PT40035, PT60080 and TM10654) were identified based on the polymorphism which clearly resolved the Nicotiana species in to resistant and susceptible.EnglishThesis