1National Bureau of Plant Genetic Resources Regional Station, Hyderabad-500030.
2National Bureau of Plant Genetic Resources, New Delhi-110012.
Abstracts of Research Papers Presented during the National Symposium of Indian Virological Society at Unit of Plant Virology, Division of Plant Pathology, Indian Agricultural Research Institute, New Delhi-110 012, October 14–1.
Millions of small farmers in the rainfed semi-arid tropics of Indian sub-continent depend on groundnut, sunflower, cotton, pulses and vegetable crops for their livelihood. A disease epidemic resulting in the death of young groundnut plants occurred in kharif 2000 in Anantapur district over an area of 2.25 lakh hectares out of 7 lakh hectares grown. Initially, the disease was suspected to be caused by Peanut bud necrosis virus (PBNV), because of the characteristic necrosis of terminal buds. In subsequent studies Tobacco streak virus (TSV) was found associated with the disease and was named as peanut stem necrosis disease (PSND). This was the first report on the occurrence of TSV on groundnut in India. TSV, a virus of quarantine importance, was recorded for the first time in India on sunflower. The virus is now known to infect economically important crops such as soybean, mungbean, urdbean, cotton, okra and marigold. The disease spreads by thrips in the presence of pollen from TSV-infected plants. Thrip transmission occurs through wounding of leaf tissue as well as infected pollen and their proximity during thrips feeding, rather than a specific virus-vector interaction. Parthenium, a symptom less carrier of TSV growing in fallow lands, roadsides and on field bunds produces several flushes during its life cycle, thus ensuing continuous supply of pollen which plays an important role in the perpetuation and spread of the disease. Seed transmission tests conducted on groundnut, sunflower, soybean, urdbean, mungbean, marigold and Parthenium indicated that the virus is not seed-transmitted in these crops. This, however, requires further testing using seeds from field-infected plants. Both PSND and PBNV occur simultaneously on groundnut under Anantapur conditions making it difficult to distinguish these two virus diseases based on field symptoms, but require assay on indicator hosts or Enzyme Linked Immunosorbent Assay. The favourable factors for PSND incidence under Anantapur conditions include rains either in late May or early June that encourages germination and growth of Parthenium; groundnut sowing in July by which time Parthenium is in full bloom; normal rains during the crop season with one or two dry spells for the thrip movement and disease spread. The above congenial conditions occurred during the current crop season. It was observed that PSND incidence ranged from 15–100% depending upon the proximity of Parthenium, and PBNV incidence ranged from 5–15% during these conditions.
