Detection and identification of the blackeye cowpea mosaic strain of Bean common mosaic virus in seeds of Vigna unguiculata sspp. from North Vietnam

Twenty-seven seed samples of catjang bean and yard long bean (Vigna unguiculata sspp.) collected from different provinces of North Vietnam were tested for the presence of the blackeye cowpea mosaic strain of Bean common mosaic virus (BCMV-B1CM), Cowpea aphid-borne mosaic virus, Cowpea mosaic virus, Cucumber mosaic virus and Southern cowpea mosaic virus using a growing-on test, ELISA, bioassay and electron microscopy. Among the 27 seedlots tested, eight catjang bean and five yard long bean seedlots were found to be infected with BCMV-B1CM serotype B. The identity of one of these isolates as BCMV-B1CM was further supported by nucleotide sequencing in the 3′ region of the genome. The incidence of seeds carrying transmissible virus ranged from 0.8 to 12.4%. In most cases, only symptomatic seedlings in a growing-on test were found infected with the virus. This is the first record of BCMV-B1CM in catjang bean and yard long bean grown in North Vietnam.