1NBPGR Regional Station, Rajendra Nagar, Hyderabad-500030.
2Division of Plant Quarantine, National Bureau of Plant Genetic Resources, New Delhi-110012.
Abstracts of the papers presented at the 16th Annual Convention and International Symposium of Indian Virological Society on “Management of Vector-Borne Viruses” at International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru-502324, Hyderabad, India, February 7–10, 2006.
Tobacco streak virus (TSV) occurred at a high incidence in a short period of 2 weeks in nearly 2,50,000 ha of groundnut grown during the 2000 rainy season in Anantapur district of Andhra Pradesh, India. Its incidence was relatively high near the field bunds, fallow and wastelands indicating that the virus occurred in various weeds. The most commonly occurring weeds were Parthenium hysterophorus, Abutilon indicum, Legasca mollis, Cleome viscosa, Euphorbia hirta, Commelina benghalensis and Tridax procumbense, all of which were found infected by TSV. In experimental transmission tests, adults of all the four thrip species (Frankliniella schultzei, Scirtothrips dorsalis, Megalurothrips usitatus and Thrips palmI) were shown to transmit TSV in groundnut, sunflower and cowpea in the presence of pollen from TSV infected parthenium, sunflower or marigold. The thrips fed on infected leaves alone did not transmit the virus. Based on experimental results, it is presumed that thrips transmission under field conditions occur in 2 ways viz., 1) pollen carrying thrips from flowers of TSV infected weeds or crop plants when colonize groundnut plants transmit the virus, and 2) wind blown pollen from TSV infected weeds or crop plants settle on groundnut plants and when these plants are colonized by thrips transmit the virus. Thrips, during their feeding, cause injury to both leaf tissue and deposited pollen and thus facilitate virus infection of the plant. The mechanism of TSV transmission by thrips is mechanical rather than a specific virus-vector interaction as observed in peanut bud necrosis tospovirus. Parthenium is widely distributed. TSV infected parthenium do not produce any symptoms (symptomless carrier). Parthenium produces several flushes during its life cycle and thus ensures continuous supply of infected pollen. All the thrip species colonize parthenium. Considering these characteristics, the role of parthenium in perpetuation of TSV and favorable weather factors for its spread to groundnut will be discussed.
