Serological and Biological Comparisons of Blackeye Cowpea Mosaic and Cowpea Aphid‐borne Mosaic Potyvirus Isolates Seed‐borne in Vigna unguiculata (L.) Walp. Germplasm

Abstract

AbstractSerological and biological comparisons were made among 45 seed‐borne isolates of blackeye cowpea mosaic (BICMV) and 54 seed‐borne isolates of cowpea aphidborne mosaic (CAbMV) potyviruses derived from cowpea seedlots or young nursery‐grown seedlings comprising 2112 germplasm accessions or pre‐introduction seedlots of Vigna unguiculata. Isolates were identified by DAS‐ELISA using polyclonal immunoglobulin G specific for these viruses. Twenty isolates of BICMV and 32 isolates of CAbMV were also compared by ACP‐ELISA with selected monoclonal antibodies and by SDS‐immunodiffusion. By all approaches, isolates of BICMV were clearly distinguished from CAbMV isolates. Isolate comparisons on selected cowpea genotypes (TVu‐401, TVu‐1582, TVu‐2657, and TVu‐3433) partitioned most isolates into two distinct groups. A few isolates seed‐borne in Indian cv. Pusa Phalguni, however, were clearly BICMV by all serological tests, but behaved as CAbMV in definitive cowpea genotypes. Although BICMV is generally considered to be a ‘new world virus’, both BICMV and CAbMV occurred in V. unguiculata seedlots originating in ‘old‐world regions’, including Afghanistan, Botswana, Nigeria, Senegal, and South Africa. Seedborne CAbMV was isolated from 6 of 155 tested US V. unguiculata Germplasm accessions originating, respectively, in Afghanistan (2), Botswana (2), India (1), and Pakistan (1).