Screening Cowpea (<I>Vigna unguiculata</I> (l) walp) lines for infection responses to some Cowpea Viruses in Nigeria

Abstract

Thirty-three cowpea varieties were screened in a screen-house in Ibadan, Nigeria for responses to four cowpea viruses; namely, Bean common mosaic potyvirus - blackeye cowpea strain (BCMV-BlC), Cowpea aphid-borne mosaic potyvirus (CABMV), Cowpea Mottle Carmovirus (CMeV) and Southern bean mosaic sobemovirus (SBMV). 33 x 5 factorial experiment in completely randomised design was used, disease severity was measured at the second and sixth weeks after mechanical inoculation of the viruses and scored from 1 (no infection) to 5 (very severe infection). Symptomless plants were serologically tested with Protein – A sandwich enzyme linked immunosorbent assay (PAS-ELISA) to distinguish lines with latent infection from none infected lines. The yield in 2000 was not significantly (p < 0.05) different from the yield in 1999, similarly, the symptoms expressed in 1999 were not significantly (p < 0.05) different from those expressed in 2000. Nine cowpea lines were severely or very severely infected by the four viruses. Three viruses; BCMV-BlC, CABMV and SBMV did not infect two lines (IT90k-284-2 and IT82D-889). In addition, CABMV and BCMV-BlC did not infect IT85F-2687 and Futo Coiled. SBMV and BCMV-BlC did not cause infection in IT86D-371, similarly, CMeV and SBMV did not cause infections CP-VAR8. CMeV and BCMV-BlC significantly (p < 0.05) reduced cowpea yield in 27 varieties, CABMV in 23 and SBMV in 14. Incidence of BCMV-BlC infection was 100% in 13 varieties, CABMV infection in 9, CMeV in 15 and SBMV in 3 varieties. IT82D-889, IT86D-880, CP-VAR8, IT85F-2687, IT86D-1010, IT90K-284-2 and Futo coiled were resistant or tolerant to the virus strains; these lines are potential breeding materials for cowpea viruses' resistance.


KEY WORDS: Cowpea viruses, Disease incidence, Cowpea, Vigna, ELISA.


Global Jnl Pure and Applied Sciences Vol.10(4) 2004: 473-478