First report of the natural occurrence of Tobacco streak virus on blackgram (Vigna mungo)

Abstract

; Fabaceae) is an important pulse crop in India,Nepal, Bangaladesh and Myanmar. Between June and September 2002, anew disease was observed in the majority of the blackgram-growing areasof India. Symptoms of the disease consisted of brown necrotic lesions onyoung leaves, with brown streaks on petioles and stems, with death ofplant in severe cases. Mechanical inoculation of plant sap from infectedplants onto various plant species – Vigna unguiculata cv. 152; Nicotianatabacum; Chenopodium amaranticolor and Gomphrena globosaproduced necrotic lesions on leaves and streaks on stems.Diseased leaf samples of blackgram tested positive for Tobacco streakvirus (TSV) by DAC-ELISA (Bhat et al., 2001) using a specific polyclonalantibody (a gift from G. Cook, Plant Protection Research Institute, SouthAfrica). Electron microscopic observations of negatively stained prepara-tions of purified virus from infected blackgram leaves revealed sphereswith a diameter of 27 nm, consistent with TSV infection. RT-PCR tests oftissue from diseased blackgram plants using primers specific for the coatprotein gene of TSV (Bhat et al., 2002) resulted in an amplicon of theexpected size: approximately 700 bp. TSV infects a wide range of hosts inIndia (Prasada Rao et al., 2003). Alternative hosts may also play a rolein disease epidemiology, since TSV infects many widely distributedweeds. For example, Parthenium hysterophorus probably plays a majorrole in the spread of TSV in peanut ( Arachis hypogaea ) (Prasada Rao et al.,2003).This is the first report of the natural occurrence of TSV on Vigna mungo.ReferencesBhat AI, Anil K, Jain RK, Chander Rao S, Ramiah M, 2001. Development of serological based assays for the diagnosis of sunflower necrosis disease.