NODULATION AND YIELD OF BUSH AND CLIMBING BEANS INOCULATED WITH RHIZOBIA STRAINS

摘要

Bean crops depend on symbiotic fixation to meet part of their nitrogen requirements. The balance is obtained from the soil. Nitrogen deficiency is the most important constraint to bean production in sub-Saharan Africa causing annual losses of more than 389,000 t per year. N is deficient in bean producing areas of Madagascar, South Africa, Zimbabwe, Malawi, Tanzania, Rwanda, Burundi, DR Congo, Uganda, Angola, Kenya and Ethiopia (Wortmann et al, 1998). Most smallholder farmers in eastern Africa do not apply fertilizers to their bean crops. This implies that productivity of bean cultivars developed for smallholder farmers in Africa depends on their ability to produce in soil low in N, and on symbiotic fixation. Although several bush and climbing beanvarieties have been developed for smallholder production in eastern Africa, the effectiveness of their symbiosis with available inoculants and native rhizobia species is not well known. Moreover, the effect of inoculation on grain yield of the new varieties and advanced lines has not been determined. Our objectives were: i) to determine variation for nodulation and nitrogen fixation in bush and climbing bean lines, and ii) study the effect of inoculating bean genotypes with rhizobia strains on grain yield.