Breeding common bean for resistance to common blight: A review

Abstract

Common blight [caused by Xanthomonascampestris pv. phaseoli Smith (Dye)] is a majorbacterial disease causing >40% seed yield andquality losses in common bean (Phaseolus vulgarisL.) worldwide. Use of resistant cultivars iscrucial for its effective, economical, and environmentfriendly integrated management andcontrol. Common blight resistant germplasmare found in the primary, secondary, and tertiarygene pools of the common bean. Substantialprogress has been made in understandingthe pathogenic variation, germplasm screeningmethods, identification of resistant germplasm,genetics of resistance, identifying and mappingmolecular markers linked with resistance quantitativetrait loci (QTL), introgressing resistancefrom the secondary and tertiary gene pools,transferring resistance from the Middle Americancommon bean landraces to Andean cultivarsand germplasm lines, and pyramiding orcombining resistance from diverse germplasmsources into common bean. Backcross, pedigree,gamete, and recurrent selection methodsor their modifications singularly or in combinationhave been used to introgress and pyramidresistance. Also, molecular markers withor without direct disease screening have beenused for breeding for resistance. However,Andean and Middle American common beancultivars with high levels of combined resistanceto less-aggressive and aggressive bacterialstrains in all aerial plant parts are not available.We will review progress achieved in breedingfor resistance, briefly describe problems faced,and discuss strategies for integrated geneticimprovement for common blight resistance forcultivar development.