Evaluation of cowpea (Vigna unguiculata (L.) Walp.) landraces to bacterial blight caused by Xanthomonas axonopodis pv. vignicola

Hammed A Durojaye,Yonnelle D Moukoumbi,Victor O Dania,Ousmane Boukar,Ranajit Bandyopadhyay,Alejandro Ortega-Beltran

doi:10.1016/j.cropro.2018.10.013

Abstract

Cowpea is an important protein source for human populations in many nations across sub-Saharan Africa (SSA). However, cowpea production is constrained by bacterial blight (CoBB) caused by Xanthomonas axonopodis pv. vignicola (Xav), a disease affecting most cowpea-growing areas. A large proportion of smallholder farmers across SSA rely on traditional cowpea landraces (CLR) to produce the crop. The International Institute of Tropical Agriculture (IITA) possesses the largest collection of cowpea germplasm, including several CLR accessions. However, screening for resistance to CoBB in most of the CLR accessions maintained at IITA has not been conducted. CoBB severity was evaluated in 103 CLR accessions from five African countries, the US, The Philippines, and Sri Lanka by artificially inoculating a highly virulent Xav strain in plants grown in a screenhouse. Highly significant (P < 0.0001) differences in susceptibilities to the disease were detected among the evaluated germplasm. Resistance was detected in several CLR accessions with two accessions from Nigeria and one from the US developing no disease symptoms. Our results indicate that several CLR accessions are valuable sources of resistance to CoBB and those could be used to breed for improved varieties with superior resistance to the disease. The resistant CLR accessions and others in IITA collection should be further investigated to identify additional beneficial traits that may contribute to the development of improved, commercially acceptable varieties.

Highlights

Cowpea (Vigna unguiculata (L.) Walp.) is the most important legume native to Africa where is grown in the drier Savannas and Sahelian regions of sub-Saharan Africa (SSA)
From the great diversity of cowpea germplasm maintained at Institute of Tropical Agriculture (IITA) Gene Bank (Boukar et al, 2012), improved genotypes have been screened for resistance to constrained by bacterial blight (CoBB) and minor emphasis has been given to cowpea landraces (CLR) accessions (Agbicodo et al, 2010; Sikirou et al, 2001)
Our results identified several CLR accessions with superior genetic backgrounds that could lead to the identification of genes, quantitative trait loci (QTL), and/or single nucleotide polymorphisms (SNP) associated with resistance to CoBB

Summary

Introduction

Cowpea (Vigna unguiculata (L.) Walp.) is the most important legume native to Africa where is grown in the drier Savannas and Sahelian regions of sub-Saharan Africa (SSA). Those regions contribute circa 70% of global cowpea production (Boukar et al, 2012). Over 12 million ha are cropped to cowpea with an annual grain production of > 6.9 million tons. Leaves, and haulms of cowpea are valued for their nutritious content for humans and livestock. Grains are rich in protein—generally composed of 25% protein—and both macro and micronutrients; leaves and haulms contain valuable nutrients and are used primarily as fodder for livestock (Singh, 2006). In SSA, cultivation of cowpea provides social and economic benefits (e.g. market access, registration of cooperatives, cash for social functions) to smallholder farmers due to its many uses (Kristjanson et al, 2005; Langyintuo et al, 2003; Langyintuo and LowenbergDeBoer, 2006)

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