Indian Journal of Virology

Viruses are one of the most important yield-reducing factors in grain legumes. Many of these viruses are seed-transmitted and spread in the field through aphid vectors. Efforts have generally not been made to generate, compile and correlate data on epidemiology so as to develop disease management strategies based on seed certification and resistance. Initiatives were thus taken recently to work on certain epidemiological parameters of seed-transmitted viruses of grain legumes viz., Bean common mosaic virus (BCMV) and urdbean leaf crinkle disease of blackgram and greengram, Black eye cowpea mosaic virus (BlCMV now a strain of BCMV) and Cowpea aphid-borne mosaic virus of cowpea, Soybean mosaic virus (SMV) of soybean and Pea seed-borne mosaic virus of pea in order to develop a model system of seed certification for some of them. Extensive field surveys were carried out for three years in nine major legume-growing states in India. This was complemented by testing seeds collected from diverse agencies. Based on results of survey and seed testing, a national map on prevalence of seed-transmitted viruses of grain legumes was prepared. Studies on field spread of the viruses revealed correlation in viral disease incidence with aphid vector population, and appreciable losses in seed yield. Based on virus spread using a known level of initial seed/seedling infection, the seed standards for certification against viruses of cowpea and soybean were proposed to be 0.5% and for pea the standards proposed were 2%. Also the findings revealed the potential virus-free areas that can be eventually exploited for virus-free seed production.