MOLECULAR CHARACTERIZATION OF TOSPOVIRUSES AND IDENTIFICATION OF HOST RESISTANCE IN CAPSICUM SP.
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Date
2016-12-27
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UNIVERSITY OF AGRICULTURAL SCIENCES GKVK, BENGALURU
Abstract
Survey was conducted in different districts of Karnataka, Andhra Pradesh and
Tamil Nadu indicated GBNV incidence of 3 to 21 per cent and the infected plants
exhibited chlorotic and necrotic ringspot symptoms. The virus was transmitted
mechanically and infects systemically to groundnut, beans, soybean, pea, watermelon,
potato, marigold and local lesions on cowpea, tobacco, datura, petunia, chenopodium and
sunhemp. The electron microscopic observation of virus infected chilli samples showed
presence of spherical particles of 80-120 nm in diameter. In DAC-ELISA, the virus
showed positive reaction to GBNV specific antisera. Using overlapping primers specific
to GBNV, complete genome was amplified and sequenced for three isolates of GBNV. The
S RNA has 3057 nt length with two ORFs (NSs and N gene) separated by intergenic region
(IGR), the M RNA contains 4815 to 4817 nt in length with two ORFs (NSm and Gp)
separated by IGR and the L RNA of 8911 nt has single ORF which codes for RNA
dependent RNA polymerase. Among 102 germplasm screened, eight genotypes are highly
resistant, eight genotypes are resistant, seven genotypes are moderately resistant. Using
RGA primers specifically amplified a DNA fragment of 0.5kb from resistant chilli
genotypes but not from susceptible genotypes. After cloning and sequencing, out of 81
clones, 60 clones showed 69.5 to 100 per cent similarities with known RGAs. Eighteen
clones of Non TIR-NBS-LRR type of RGAs had similar homology with putative late blight
resistance genes of Nicotiana tabacum, N. tomentosiformis, Solanum lycopersicom, S.
pennelli, S. tuberosum and PVr9 potyvirus resistance protein. Twelve clones of TIR-NBSLRR
type of RGAs had similar homology with TMV resistance protein N like gene of
Capsicum annuum, Nicotiana tabacum, N. tomentosiformis, Solanum aculeatissimum, S.
bulbocastanum, S. esculentum, S. pennelli and S. tuberosum. RGAs identified will be
useful in marker-assisted breeding for GBNV resistance in chilli.
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