Yellow vein mosaic disease symptoms occur frequently in pumpkin in India. Diseased plants show vein yellowing, which sometimes coalesces to form chlorotic patches. Infected plants are stunted and flowers drop prematurely, greatly reducing yields. Diseased plants are infected by a begomovirus, designated pumpkin yellow vein mosaic virus (PYVMV), which is transmitted readily and in a persistent manner by the whitefly, Bemisia tabaci. Transmission of PYVMV requires minimum acquisition and inoculation access periods of 30 min and 10 min, respectively. The minimum latent period in the insect is 6 h and the virus persists in the vector for at least 8 days. PYVMV has a narrow host range consisting of a small number of cucurbit species and some tobacco cultivars. It was detected serologically in diseased plants and in viruliferous B. tabaci using polyclonal antibodies in a double-antibody sandwich enzyme-linked immunosorbent assay. Reactions with monoclonal antibodies in a triple-antibody sandwich ELISA showed that PYVMV has an epitope profile distinct from those of other begomoviruses from the Indian sub-continent. Polymerase chain reaction amplified fragments from the putative viral coat and movement protein genes. Based on comparative phylogeny of complete coat protein gene sequences, PYVMV was most similar to the bipartite Tomato leaf curl New Delhi virus from India and appears to be a new strain of this virus.

Summary Sterility mosaic disease (SMD), an important biotic constraint on pigeonpea (Cajanus cajan) in the Indian subcontinent, is caused by Pigeonpea sterility mosaic virus (PPSMV) transmitted by the eriophyid mite, Aceria cajani. Distinct PPSMV isolates occur in different geographical regions and broad‐based resistance to all these isolates is scarce in cultivated pigeonpea germplasm. Wild relatives of pigeonpea, which are known to possess resistance to several pests and diseases, were evaluated for broad‐based SMD resistance. One hundred and fifteen wild Cajanus accessions from six species (C. albicans, C. platycarpus, C. cajanifolius, C. lineatus, C. scarabaeoides and C. sericeus) were evaluated against three PPSMV isolates prevailing in peninsular India. Evaluations were done under greenhouse conditions in endemic locations of each isolate through mite‐mediated virus inoculation. Fifteen accessions showed resistance to all three isolates: ICP 15614, 15615, 15626, 15684, 15688, 15700, 15701, 15725, 15734, 15736, 15737, 15740, 15924, 15925 and 15926. Most of the wild accessions did not support mite multiplication. The majority of the accessions resistant to PPSMV following inoculations with viruliferous mites were susceptible by graft inoculation, suggesting that vector resistance is conferring resistance to infection with PPSMV. The 15 accessions identified as being resistant to infection to all three virus isolates tested are cross compatible with pigeonpea by traditional breeding. They are therefore useful for exploitation in breeding programmes to increase both the level of SMD resistance and to diversify its genetic base in the cultivated pigeonpea gene pool.

Resistance to tomato leaf curl virus disease (ToLCVD) in tomato (Solanum lycopersicum) is scarce but was developed recently in three open pollinated (OP) varieties (Sankranthi, Nandi and Vybhav), which are now available for cultivation in South India. Hybrids with superior yield capabilities, however, are a preferred choice of cultivation by farmers but hybrids are highly susceptible to ToLCVD. In order to develop virus resistant tomato hybrids, the three OPs were crossed with 12 tomato genotypes with superior agronomic characteristics. From the crosses, 20 hybrids were selected (named BLRH-1 to BLRH-20, Bangalore leaf curl virus-resistant hybrid) and evaluated for their resistance to ToLCVD at the University of Agricultural Sciences, Bengaluru, South India, both through whiteXy-mediated inoculations in the glasshouse and natural infection in the Weld during summer 2005. Their growth and fruit yield parameters were compared against the popularly grown hybrids and OPs. DiVerences occurred between hybrids in disease incidence, spread, symptom severity and fruit yield. Of the 20 hybrids evaluated, 11 were found resistant to ToLCVD in the Weld, but only three (BLRH-3, BLRH-9 and BLRH-16) remained resistant when challenged with high virus inoculum pressure in the glasshouse through whiteXy-mediated inoculations. None of the six commercially available hybrids tested was found resistant to ToLCVD. An examination of the extent of heterosis in resistant hybrids for both quantitative and qualitative characters over the popularly grown hybrid, US-618, indicated a major improvement in virus resistance, yield and fruit quality. All the twenty hybrids yielded signiWcantly more than US-618, and of these, BLRH-3 and BLRH-16 were considered the best with yields over ca. 60 t/ha and resistant to virus both in the glasshouse and Weld.

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Bunchy top disease of banana caused by Banana bunchy top virus (BBTV, genus Babuvirus family Nanoviridae) is one of the most important constraints in production of banana in the different parts of the world. Six genomic DNA components of BBTV isolate from Kandy, Sri Lanka (BBTV-K) were amplified by polymerase chain reaction (PCR) with specific primers using total DNA extracted from banana tissues showing typical symptoms of bunchy top disease. The amplicons were of expected size of 1.0-1.1 kb, which were cloned and sequenced. Analysis of sequence data revealed the presence of six DNA components; DNA-R, DNA-U3, DNA-S, DNA-N, DNA-M and DNA-C for Sri Lanka isolate. Comparisons of sequence data of DNA components followed by the phylogenetic analysis, grouped Sri Lanka-(Kandy) isolate in the Pacific Indian Oceans (PIO) group. Sri Lanka-(Kandy) isolate of BBTV is classified a new member of PIO group based on analysis of six components of the virus.