Developing cowpea and bean genotypes with tolerance to bruchid beetle

Cowpea and beans are important grain legume pulses in sub-Saharan Africa, but yields have been characteristically low as a result of both abiotic and biotic stresses. Among the biotic stresses infestation by the bruchid beetles Callosobruchus maculatus and Acanthoscelides obtectus are major problems which cause yield losses of up to 100% in cowpea and bean, respectively. To address this problem a collaborative research is being undertaken between University of Zambia (Zambia) and the Department of Agricultural Research Services (DARS) in Malawi whose objectives are to develop cowpea genotypes with tolerance to Callosobruchus maculatus and to improve efficiency of selection through identification of molecular markers linked to Acanthoscelides obtectus in beans. In Zambia eight cowpea genotypes (mutants and their parents) and two other popular susceptible genotypes (Musandile and Namuseba) are being evaluated. These were planted in January 2015 in three locations (University of Zambia (UNZA), Golden Agriculture Research Trust (GART) and Msekera in Zambia using a randomised complete block design (RCBD) with three replications. Storage evaluations were done in the Laboratory at the University of Zambia. In Malawi, similar trials were conducted in January 2016 and evaluations are yet to be done. For molecular mapping, a cross involving a susceptible and resistant bean genotype [Lyambai x Carioca] is now being advanced to F4. The results obtained so far showed that they were significant differences (p< 0.05) among genotypes with regards to mean bruchid adults’ emergence across locations in Zambia. The interaction between genotype x location was not significant. The locational mean genotypic performance was significant (p< 0.05) at UNZA and GART. From the experiment the mutant LT 11-5-2-2 and BB 14-16-22 were identified to be tolerant to bruchid attack in and across both locations and they outperformed their parental genotypes. For Malawi field characterization has been done and lab storage evaluations are yet to be done