Abstract
Nearly all mungbean cultivars are completely susceptible to seed bruchids (Callosobruchus chinensis and Callosobruchus maculatus). Breeding bruchid-resistant mungbean is a major goal in mungbean breeding programs. Recently, we demonstrated in mungbean (Vigna radiata) accession V2802 that VrPGIP2, which encodes a polygalacturonase inhibiting protein (PGIP), is the Br locus responsible for resistance to C. chinensis and C. maculatus. In this study, mapping in mungbean accession V2709 using a BC11F2 population of 355 individuals revealed that a single major quantitative trait locus, which controlled resistance to both C. chinensis and C. maculatus, was located in a 237.35 Kb region of mungbean chromosome 5 that contained eight annotated genes, including VrPGIP1 (LOC106760236) and VrPGIP2 (LOC106760237). VrPGIP1 and VrPGIP2 are located next to each other and are only 27.56 Kb apart. Sequencing VrPGIP1 and VrPGIP2 in “V2709” revealed new alleles for both VrPGIP1 and VrPGIP2, named VrPGIP1-1 and VrPGIP2-2, respectively. VrPGIP2-2 has one single nucleotide polymorphism (SNP) at position 554 of wild type VrPGIP2. This SNP is a guanine to cystine substitution and causes a proline to arginine change at residue 185 in the VrPGIP2 of “V2709”. VrPGIP1-1 has 43 SNPs compared with wild type and “V2802”, and 20 cause amino acid changes in VrPGIP1. One change is threonine to proline at residue 185 in VrPGIP1, which is the same as in VrPGIP2. Sequence alignments of VrPGIP2 and VrPGIP1 from “V2709” with common bean (Phaseolus vulgaris) PGIP2 revealed that residue 185 in VrPGIP2 and VrPGIP1 contributes to the secondary structures of proteins that affect interactions between PGIP and polygalacturonase, and that some amino acid changes in VrPGIP1 also affect interactions between PGIP and polygalacturonase. Thus, tightly linked VrPGIP1 and VrPGIP2 are the likely genes at the Br locus that confer bruchid resistance in mungbean “V2709”.
Highlights
Mungbean [Vigna radiata (L.) Wilczek] is an important legume crop of Asia
Seeds of “V2709” were free from damage by C. chinensis and C. maculatus, while seeds of “KPS1” were all damaged by both bruchid species
The resistance was determined based on the percentage of seeds damaged by bruchids. aPhenotypic variance explained by the Quantitative Trait Locus (QTL)
Summary
Mungbean [Vigna radiata (L.) Wilczek] is an important legume crop of Asia. It is cultivated on ∼6 million hectares, mainly in Asia (Somta et al, 2007). Bruchids or seed weevils (Coleoptera: Bruchidae) are serious pests that damage legume seeds after harvest. Azuki bean weevil (Callosobruchus chinensis L.) and cowpea weevil (Callosobruchus muculatus F.) are the major bruchid species that feed on seeds of mungbean and other food legumes, including cowpea (Vigna unguiculata L.), black gram [Vigna mungo (L.) Hepper], Bambara groundnut [Vigna subterranea (L.) Verdc.], azuki bean [Vigna angularis (Willd.) Ohwi and Ohashi], soybean [Glycine max (L.) Merr.], chickpea (Cicer arietinum L.) and pigeon pea [Cajanus cajan (L.) Millsp.]. Bruchids are controlled by chemical fumigation and dusting. These chemicals are harmful to humans and the environment, and increase production costs. A major goal in mungbean breeding programs is to develop bruchid-resistant cultivar(s) (Somta et al, 2007; Srinives et al, 2007)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
