BIOLOGICAL AND MOLECULAR CHARACTERIZATION OF BEGOMOVIRUSES CAUSING TOBACCO LEAF CURL VIRUS DISEASE IN KARNATAKA
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Date
2018-09-24
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University of Agricultural Sciences, GKVK Bengaluru
Abstract
Tobacco 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.