Abstract
Over 400 genetically diverse lines of cowpea were planted at three locations in West Africa, with or without fertilizer N applied. At all locations many of the cultivars responded positively to N fertilization as shown by shoot fresh weight at five to six weeks after planting, indicating inadequate infectivity or efficacy of indigenous rhizobia and a potential for improvement by use of inoculant. From a selection of the cowpeas, rhizobia have been isolated and are being characterized to identify effective and competitive strains for use in inoculant trials, and to gain an understanding of strain diversity within and between locations. The diversity of rhizobia has been investigated in terms of colony type, ability to grow at 37°C, ability to nodulate groundnut, soya bean, pigeon pea and mung bean, intrinsic antibiotic resistance and serological properties using the enzyme linked immunosorbent assay.
