First report of the natural occurrence of Tobacco streak virus on blackgram (Vigna mungo).
Between June and September 2002, a new disease was observed in the majority of the black gram-growing areas of India. Symptoms of the disease consisted of brown necrotic lesions on young leaves, with brown streaks on petioles and stems, with death of plant in severe cases. Mechanical inoculation of plant sap from infected plants onto various plant species (Vigna unguiculata cv. 152, Nicotiana tabacum, Chenopodium amaranticolor and Gomphrena globosa) produced necrotic lesions on leaves and streaks on stems. The pathogen was identified as Tobacco streak virus (TSV) based on electron microscopic observations and molecular investigations. This is thought to be the first report of the natural occurrence of TSV in black gram.