Quantitative trait loci analysis of brown blotch resistance in cowpea variety KN1

Erik W Ohlson,Michael P Timko,Paco Sérémé,Mahamadou Sawadogo,Gilles I Thio

doi:10.1007/s11032-018-0867-1

Abstract

Cowpea is one of the most important crops in West Africa and is essential for the region’s food and nutrition security and economic development. Consequently, improving its agronomic performance and yield is a desirable goal. Brown blotch disease, caused by the fungal pathogen Colletotrichum capsici, is an important constraint of cowpea productivity, and at present, only limited genetic resources are available for breeding improved brown blotch-resistant varieties. The current study has characterized the genetic basis for brown blotch resistance conferred by the cowpea cultivar KN1 and identified a major dominant quantitative trait locus (QTL) for resistance on chromosome Vu02. A segregating F2 population (n = 200), derived from a cross between KN1 and brown blotch-susceptible Tiligre (KVx775-33-2G), was developed and scored for disease severity following controlled inoculation. A subset of the population (n = 94) was genotyped with 99 newly developed allele-specific polymerase chain reaction (AS-PCR) markers, and multiple interval mapping was performed. One major and three minor QTL were identified. This is the first reported mapping of QTL conferring resistance to C. capsici in cowpea, and it is expected that the markers identified here will be a valuable resource for developing elite cowpea cultivars with resistance to brown blotch.

Highlights

Cowpea (Vigna unguiculata (L.) Walp.) is an important legume grown for food and fodder in the semi-arid tropics
Worldwide cowpea production is estimated at 6.5 million metric tons annually, with 80% of production occurring in West Africa (Boukar et al 2016)
The genetic map consisted of 99 markers and 11 linkage groups, corresponding to the 11 cowpea chromosomes (Vu01–Vu11)

Summary

Introduction

Cowpea (Vigna unguiculata (L.) Walp.) is an important legume grown for food and fodder in the semi-arid tropics. An increasing pool of genomic data (Timko et al 2008; Muñoz-Amatriaín et al 2016; Vigna unguiculata v1.0, NSF, UCR, USAID, DOE-JGI, http://phytozome.jgi.doe.gov/) has facilitated the identification of genetic markers and quantitative trait loci (QTL) associated with resistance to several important cowpea pests and diseases. These pests and diseases include Striga gesnerioides (Ouédraogo et al 2001, 2002b; Li and Timko 2009; Ouedraogo et al 2012), aphids (Huynh et al 2015; Kusi et al 2018), thrips (Omo-Ikerodah et al 2008; Muchero et al 2010), root-knot nematodes (Ouédraogo et al 2002a; Huynh et al 2016), Fusarium wilt (Ouédraogo et al 2002a; Pottorff et al 2012), Macrophomina phaseolina (Muchero et al 2011), Cercospora leaf spot (Duangsong et al 2016), bacterial blight (Shi et al 2016), and various mosaic viruses (Ouédraogo et al 2002a). Despite significant progress developing molecular breeding tools for cowpea breeders, economically important diseases still lack genetic markers including brown blotch disease, caused by the fungal pathogen Colletotrichum capsici [Syd.] Butler and Bisby

Methods

Results

Conclusion