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

Abstract

Abstract Cowpea 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 F 2 lines from a cross between MU9 (susceptible) and WC42 (resistant) were genotyped with 2753 single nucleotide polymorphism markers. The F 2:3 seeds were screened for resistance to cowpea bruchids using a no‐choice experiment. Significant differences were observed among the F 2:3 lines for bruchid‐resistance traits, except on oviposition. The Dobie susceptibility index scale grouped the F 2:3 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 (MDP6.1 MW , R 2 = 25.9%) and a co‐localized QTL region on Vu09 for number of adult bruchid emergence (NEI9.1 MW , R 2 = 28.6%), number of eggs per 10 seeds (NE9.1 MW , R 2 = 18.8%), average number of exit holes on seeds (ANH9.1 MW , R 2 = 19.6%), and seed weight ( R 2 = 15.6%–16.3%), respectively. Therefore, markers linked to the QTL identified in this study including MDP6.1 MW , NEI9.1 MW , and ANH9.1 MW can be validated for marker‐assisted selection to fasten breeding for resistance to bruchid in cowpea.