Effects of soil management and cropping options on yields of drought tolerant bush bean varieties in two agro-ecologies in central Malawi

United States Agency for International Developmen

Inheritance of resistance to common bacterial blight in common bean

The common bean (Phaseolus vulgaris L.) is an important grain legume crop in Malawi where it is grown by small holder farmers for food as well as for sale. Among the many diseases that limit crop productivity is the common bacterial blight caused by Xanthomonas axonopodis pv phaseoli (Xap). Effective breeding for resistance to Xap requires understanding of the model of inheritance for resistance. A study to determine the inheritance of resistance to Xap in common bean was carried out in Malawi. Two established bean varieties originating from local landraces in Malawi (Chimbamba and Nasaka), plus one line (RC 15) from the breeding programme at Bunda College of Agriculture, were used as recipient (susceptible) parents; while Vax 6 from CIAT was the donor (resistant) parent. The progenies were advanced to F2 generations in greenhouses. The F2 populations were evaluated for resistance to Xap. The results showed that one recipient parent, Chimbamba, which is supposedly homogeneous, behaved like a segregating population and, therefore, modified the phenotypic ratios of the progenies. A Chi-square test using data generated from populations resulting from the three recipient parents showed that the inheritance of resistance to Xap was controlled by two major genes with possible minor genes involvement. The same was true when a Chi-square test was used to analyse the pooled data across populations generated from the three recipient parents (Chimbamba, Nasaka and RC 15), suggesting that inheritance of resistance to Xap was controlled by two major gene

Inheritance of halo blight resistance in common bean

Halo blight caused by (Pseudomonas syringe pv. phaseolicola (Burkh) (Psp)) is an important disease of common bean (Phaseolus vulgaris L.) world-wide. Several races of the Psp exist and likewise some sources of resistance in common bean have been identified. CAL 143, is a CIAT-bred common bean line, which was released as a variety in Malawi and several other countries in southern Africa. It possesses good resistance to Psp. However, the mode of inheritance for resistance to Psp in CAL 143, which is essential for devising a proper breeding strategy for developing bean varieties with durable resistance, has not been established. A study was conducted on the mode of inheritance for resistance to Psp using populations generated from crosses between three susceptible female parents (Chimbamba, Nasaka, and RC 15) and CAL 143 as a resistant male parent. The progenies were advanced to F2 and F3 generations in greenhouses at Bunda College of Agriculture and Bvumbwe Research Station. The F2 and F3 populations were evaluated for resistance to Psp in the field at Dedza and Ntchenachena. The results from both F2 and F3 populations indicated that there was a single dominant gene mode of inheritance for resistance to Psp in CAL 143. This monogenic resistance can be utilised easily and quickly in breeding for resistance to Psp. CAL 143 is, therefore, an ideal source of resistance and a valuable parent in breeding for resistance to Psp in Malawi

Performance of parental genotypes and inheritance of Angular Leaf Spot Phaeosariopsis griseola) resistance in the common bean (Phaseolus vulgaris)

Two studies, one on performance of six common bean parental genotypes and another on inheritance of resistance to Phaeosariopsis griseola (Pg) in the common bean were carried out in Malawi. Common bean entries namely; Chimbamba, Nasaka, RC 15, CAL 143 and Mexico 54 were evaluated on station in the 2004/2005 growing season at Bunda, Dedza, Ng'onga and Ntchenachena sites. The second study started by generating F1s and then F2 and F3 seeds in greenhouse at Bunda College. CAL 143 and Mexico 54 were sources of Pg resistance genes while Chimbamba, Nasaka and RC 15 were susceptible recipient parents. Following green house trials, Pg resistance was evaluated on station in the same sites. CAL 143 was highest yielding but unstable across sites. RC 15 was stable and gave the highest yield at the dry-spell-stricken Ng onga whereas Mexico 54 was superior at Ntchenachena but highly unstable across sites. Yield was strongly correlated to number of effective pods per plant in all genotypes. The inheritance study showed that resistance to Pg in the common bean is controlled by one gene using both CAL 143 and Mexico 54 as resistant parents