Construction of High-Density Genetic Map and Identification of a Bruchid Resistance Locus in Mung Bean (Vigna radiata L.)

Abstract

Mung bean (Vigna radiata L.) is an economically important grain legume cultivated in Asian countries. High-density genetic linkage is a valuable and effective tool for mapping quantitative trait loci (QTL). In the current study, a high-resolution genetic map containing 4,180 single-nucleotide polymorphisms (SNPs) was assigned to 11 linkage groups (LGs) and spanning 1,751.39 cM in length was constructed for mung bean, and the average distance between adjacent markers was 0.42 cM. Bruchids (Callosobruchus spp.) cause significant damage to and loss of legume seeds. A locus for bruchid resistance was detected. The gene Vradi05g03810, encoding a probable resistance-specific protein, was found to be the most likely key candidate gene in mung beans. A 69-bp sequence deletion was identified in the coding region by comparing the cDNA sequences of bruchid-resistant and bruchid-susceptible lines. This SNP-based high-density linkage map is one of the first to be constructed across the mung bean genome. This map will not only facilitate the genetic mapping of genes or complex loci that control important agronomic traits but also offer a tool for promoting future genetics and comparative genomic studies in Vigna.

Keywords: SLAF-seq; SNP; bruchid resistance; genetic map; mung bean (Vigna radiata L.).

FIGURE 1

Distribution of SLAF markers on 11 LGs of mung bean. A black bar indicates a marker. The x-axis represents linkage group number and the y-axis indicates genetic distance (cM).

FIGURE 2

Frequency distribution of the percentage of seeds damaged.

FIGURE 3

Results of genetic association analysis to identify regions of the mung bean genome associated with resistance to bruchid infestation. The x-axis shows the physical positions of the SLAF marker in different chromosomes. The y-axis shows the Δ (SNP-index) of the SLAF marker. Every color dot represents Δ(SNP-index) of the SLAF marker in every chromosome. The black lines are the loess fitting curve of Δ(SNP-index) based on smooth values. The grey dotted line is the threshold of the smooth value of Δ (SNP-index).

FIGURE 4

Sequence analysis of RSP1 gene. (A) Comparison of the amino acid sequences of bruchid-resistant and susceptible lines. (B) PCR detection of InDel marker in bruchid-resistant lines (TC1966 and VC6089A) and susceptible lines (VC 1973A, VC2778A, and Zhonglv No.1).