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A survey for Peanut bud necrosis virus (PBNV), Watermelon bud necrosis virus (WBNV), Capsicum chlorosis virus (CaCV), and Iris yellow spot virus (IYSV) was conducted between 2002 and 2009 in the major vegetable-growing areas in India. PBNV was documented widely in tomato and chili peppers in 14 states representing southern, north-western, north-eastern, and central regions and WBNV was predominantly detected in watermelons and cucurbits in all except north-eastern regions. In addition, the expanded host range of PBNV to watermelons and other cucurbits and WBNV to tomato and chili peppers was observed leading to natural mixed infection of the two viruses. IYSV was found in onion in southern, central, and north-eastern regions and CaCV in tomato and chili peppers in northern and southern regions, respectively. Phylogenetic analysis of the nucleocapsid gene revealed segregation of field isolates of PBNV and WBNV into two distinct subclades, whereas isolates of CaCV and IYSV each clustered into a single clade. A proposal for establishing WBNV as a distinct tospovirus species is made based on the molecular characterization of small- (S) and medium- (M) RNA segments.

During 2002-03, field-infected onion ( Allium cepa ) plants, exhibiting characteristic symptoms of chlorotic spindle-or diamond-shaped lesions on the leaves and scapes with twisting or bending flower-bearing stalks, were observed in the Jalna and Nasik regions of Maharashtra, India. In the advanced stages, single spindle-shaped chlorotic lesions coalesced, leading to withering of leaves and flower-bearing stalks. The disease was transmitted to a number of virus-indicator plants by mechanical inoculation using phosphate buffer (0·01 m sodium sulfate, pH 7·0, containing 0·1% sodium sulfite). Inoculated Nicotiana benthamiana plants produced systemic necrotic lesions, eventually resulting in dieback and wilting of the plants, while Nicotiana tabacum (varieties Xanthi NC, White Burley, Samsun and GT-4) and Nicotiana clevelandii produced local chlorotic ring spots 3-6 days after inoculation. In Vigna unguiculata , necrotic local lesions developed 3-4 days postinoculation, while Nicotiana rustica failed to produce any symptoms and did not become infected.Field-infected onion samples and glasshouse-inoculated plants were tested by ELISA using the following antisera: Tobacco streak virus (DSMZ AS-0615); Watermelon silver mottle virus (DSMZ AS-0118); Iris yellow spot virus (DSMZ AS-0528); Tomato spotted wilt virus (DSMZ AS-0105); Impatiens necrotic spot virus (DSMZ AS-0115); Chrysanthemum stem necrosis virus (DSMZ AS-0529); Peanut bud necrosis virus (ICRISAT); and Potato virus Y (DSMZ AS-0573), utilizing the respective positive control samples. Field-infected onion samples and the respective mechanically inoculated tobacco plants reacted strongly with Iris yellow spot virus (IYSV) antisera, but failed to react with any of the other antisera tested. RT-PCR using primers designed to the capsid gene and flanking sequences of IYSV (GenBank accession number AF001387) produced the expected 925-bp amplicon from infected but not healthy onions. The results of symptomatology, host range, ELISA and RT-PCR indicate that the causal agent is a strain of IYSV, which is a new report from an important oniongrowing region of Maharashtra State, India. This virus has been reported as a potentially devastating pathogen of onion in Europe (Cortes et al ., 1998), Israel (Gera et al ., 1998 and the USA (Gent et al ., 2004).

A survey conducted in pepper-growing tracts of Karnataka State, covering 165 fields in 33 villages, revealed the occurrence of many pepper mosaic diseases. Based on reactions on selected test plants, the viruses were identified as pepper vein banding virus (PVBV), pepper veinal mottle virus, potato virus Y, cucumber mosaic virus, and tobacco mosaic virus. Among these, PVBV was the most prevalent. PVBV was purified from infected leaves of Capsicum annuum cv. California Wonder. Electron microscopy revealed flexuous rod-shaped particles in the purified preparations. The coat protein (CP) molecular weight was 35,000, which is similar to members of the Potyvirus group. As in other potyviruses, the CP underwent proteolytic degradation to a fragment with a molecular weight of 31,000. Both of these bands cross-reacted with antibodies against tobacco etch virus in Western blots. Polyclonal antibodies were produced against PVBV. Cross-reactivity studies with other potyviral antisera showed that PVBV is serologically closer to peanut mottle virus than to peanut stripe virus or sorghum potyvirus. N-terminal sequence analysis of the intact CP and trypsin-resistant core revealed that PVBV is a distinct member of the Potyvirus group.

Two isolates of Capsicum chlorosis virus (CaCV, genus Tospovirus) from tomato (CaCV-To-Ind) and chilli (CaCV-Ch-Pan), collected from Haryana and Uttar Pradesh states of northern India respectively, were compared. A comparison of the amino acid sequences of their N genes revealed more than 96% identity, confirming that the virus isolates in India have a high degree of sequence conservation and are closely related to Australian isolates. Analysis of the host range of CaCV revealed no biological difference between the isolates, but they differed from CaCV-Australia. The nucleotide sequences of S, M and L RNA of CaCV-Ch-Pan were determined. The S RNA contains 3,105 nucleotides (nt), with NSs and N genes of 1,320 and 828 nt, respectively. The M RNA consists of 4,821 nt, with an NSm gene of 927 nt and a Gn/Gc gene of 3,366 nt. The intergenic regions of S and M RNA contain 824 and 425 nt, respectively. The L RNA consists of 8,912 nt, with an RNA-dependent RNA polymerase gene of 8,634 nt.