Comparative susceptibility of Kenyan improved cowpea varieties to

Abstract

This study was conducted to determine whether any of 3 improved cowpea varieties: 419, K80 and M66 from a cowpea improvement programme at Katumani in the Eastern Province of Kenya had any advantages in terms of bruchid infestation that could be exploited in subsequent breeding work. The varieties were compared in the laboratory for susceptibility to the cowpea bruchid, Callosobruchus maculatus (F.). They were also exposed to field infestation by cowpea bruchid species that infest the crop at Katumani. In the laboratory, seeds and pods were used to compare: (i) number of eggs laid; (ii) duration of development; (iii) number, weight and longevity of adults; (iv) sex ratio; (v) fecundity of females and (vi) percent and weight loss caused by the bruchid larvae on the hosts. In the field, the varieties were planted during both the long and Short Rains. After harvesting, seed samples were incubated for emergence of adult bruchids. Laboratory investigation revealed that none of the Katumani improved cowpea varieties were resistant to C. maculatus. In the field all the 3 varieties were infested by 3 species of cowpea bruchids: Callosobruchus rhodesianus (Pic.), C. chinensis (L.) and C. maculatus. In addition, varieties, 419 and M66 were infested by the bean bruchid Acanthoscelides obtectus (Say) and M66 was infested by another cowpea bruchid, Bruchidius atrolineatus (Pic.). We conclude that there is need to search for bruchid resistance in other cowpea lines, which could be incorporated in these already improved varieties to enhance their storing qualities.