Mapping of quantitative trait loci associated with resistance to bruchids (Callosobruchus maculatus) in cowpea (Vigna unguiculata)

Abstract

AbstractCowpea bruchid (Callosobruchus maculatus) is a major storage insect pest that reduces cowpea (Vigna unguiculata) yield and seed quality, making it unsafe for consumption. This study seeks to identify and map quantitative trait loci (QTLs) associated with resistance to cowpea bruchids. A total of 120 F2 lines from a cross between MU9 (susceptible) and WC42 (resistant) were genotyped with 2753 single nucleotide polymorphism markers. The F2:3 seeds were screened for resistance to cowpea bruchids using a no‐choice experiment. Significant differences were observed among the F2:3 lines for bruchid‐resistance traits, except on oviposition. The Dobie susceptibility index scale grouped the F2:3 lines from moderately resistant to highly susceptible, hence no highly resistant line was identified in this study. Ten QTL for resistance to bruchids were identified on chromosomes Vu02, Vu03, Vu04, Vu06, Vu08, Vu09, and Vu11. Two major QTLs were identified and mapped: on Vu06 for median development period (MDP6.1MW, R2 = 25.9%) and a co‐localized QTL region on Vu09 for number of adult bruchid emergence (NEI9.1MW, R2 = 28.6%), number of eggs per 10 seeds (NE9.1MW, R2 = 18.8%), average number of exit holes on seeds (ANH9.1MW, R2 = 19.6%), and seed weight (R2 = 15.6%–16.3%), respectively. Therefore, markers linked to the QTL identified in this study including MDP6.1MW, NEI9.1MW, and ANH9.1MW can be validated for marker‐assisted selection to fasten breeding for resistance to bruchid in cowpea.