NATURAL OCCURRENCE OF 5 SEED-BORNE COWPEA VIRUSES IN PAKISTAN

A total of 151 cowpea leaf samples with viruslike symptoms were collec ted from 13 districts of Punjab and North-West Frontier Province (NWFP ) of Pakistan during the summers of 1990 and 1991. Desiccated samples were tested by direct antigen coating (DAC) ot double antibody sandwic h (DAS) enzyme-linked immunosorbent assay (ELISA) for the presence of seven viruses known to be seedborne in cowpea: blackeye cowpea mosaic (BlCMV) and cowpea aphid-borne mosaic (CABMV) potyviruses, cucumber mo saic (CMV) cucumovirus, cowpea mosaic (CPMV) and cowpea severe mosaic (CSMV) comoviruses, cowpea motile carmovirus (CPMoV), and southern bea n mosaic sobemovirus (SBMV). One or more seedborne viruses were detect ed in 47% (71 of 151) of the symptomatic plant samples. The viruses de tected and the percent incidence were: CABMV, 29%; SBMV, 21%; CSMV, 17 %; BlCMV, 8%; and CPMoV, 4%. Neither CMV nor CPMV was detected. Seven cowpea seed lots representing two commercial seed types and seven loca tions in Punjab and NWFP were collected for tests of the same seven se edborne viruses. Only CABMV was seed-transmitted, and only in four of seven seed lots, at frequencies of <1 to 7%. Likewise, although leaf s amples collected from plants of a local Punjab cultivar contained four ELISA-detectable seedborne viruses (BlCMV, CABMV, CSMV, and SBMV), on ly CABMV was transmitted through seeds (7% frequency) from these plant s. None of the seven seedborne viruses tested for were detected in 80 of 151 virus-symptomatic samples, suggesting infection with other viru ses. This is believed to be the first record of the natural occurrence of BlCMV, CABMV, CPMoV, CSMV, and SBMV in Pakistan and the first repo rt of CPMoV outside of Africa.