Varietal resistance in haricot beans (Phaseolus vulgaris L.) to postharvest infestation by Zabrotes subfasciatus Boheman

Abstract

Fifty-six, 32, and 65 indigenous and exotic haricot bean genotypes were screened for their resistance against Mexican Bean Weevil Zabrotes subfasciatus (Boheman) (Coleoptera: Bruchidae) damage in 1996, 1997 and 1998, respectively, in the laboratory at Bako Agricultural Research Center, Western Ethiopia. Thirty of the genotypes were received from the Internationa! Center for Tropical Agriculture (CIAT) whereas the rest were obtained from Bako and Melkassa Research Centers. Data on the number of eggs laid per seed, median development time (MDT), number of progeny developing successfully into adults, percentage grain damage (%gd) and
susceptibility index were considered for evaluation. Variations were observed among the genotypes tested against attack byZabrotes. All of the 25 CIAT accessions (RAZ coded lines) were resistant (with low progeny emergence, low percentage of grain damage and longer MDT) to Zabrotes. From the commercial bean varieties, only Roba-1 exhibited resistance to the pest. The rest of the genotypes including bean progenies from the Bean Improvement Programme as well as materials from the bean stem maggot resistance breeding had high progeny weevil emergence, percent grain damage and indices of susceptibility. The overall result of this experiment indicated that except RAZ lines and Roba-1, all the other bean genotypes tested were found tobe susceptible to attack by Zabrotes.