Serological Screening of Cowpea Genotypes for Resistance against Cowpea Aphid Borne Mosaic Virus Using DAS-ELISA

Cowpea (Vigna unguiculata (L.) Walp), an important protein rich arid legume crop is susceptible to number of fungal, bacterial and viral diseases that severely limit the productivity. A set of 92 diverse cowpea genotypes including varieties, mutants, advanced breeding lines, exotic and indigenous collections were serologically screened for resistance against Cowpea Aphid Borne Mosaic (CABM) virus using DAS-ELISA. The genotypes grown in triplicate in a randomized block design at Trombay were mechanically inoculated with CABM virus and the resistance or susceptible reactions of each of the genotypes were recorded visually as well as serologically. Based on the extent of symptoms and serological reactions, the cowpea genotypes were classified as: highly resistant, plants without symptoms and negative for serology; resistant, plants with mild mosaic (<25%) and positive for serology; susceptible, plants with mosaic (26-75%) and positive for serology and highly susceptible, plants with severe mosaic (>75%) and other systemic symptoms and positive for serology. The study resulted in the identification of 13 highly resistant, 24 resistant, 50 susceptible and 5 highly susceptible genotypes. The chlorophyll index of susceptible genotypes as measured by SPAD chlorophyll meter was almost half that of resistant genotypes. The highly resistant genotypes against CABM virus identified in the present study after due confirmation would be incorporated in the breeding programme to develop resistance in elite genetic backgrounds.