Lobaton JD, Miller T, Gil J, Ariza D, de la Hoz JF, Soler A, Beebe S, Duitama J, Gepts P, Raatz B.

Plant Genome. 2018 Jul;11(2).

Abstract

Common bean ( L.) is the most important grain legume for human consumption and is a major nutrition source in the tropics. Because bean production is reduced by both abiotic and biotic constraints, current breeding efforts are focused on the development of improved varieties with tolerance to these stresses. We characterized materials from different breeding programs spanning three continents to understand their sequence diversity and advance the development of molecular breeding tools. For this, 37 varieties belonging to , (A. Gray), and L. were sequenced by whole-genome sequencing, identifying more than 40 million genomic variants. Evaluation of nuclear DNA content and analysis of copy number variation revealed important differences in genomic content not only between and the two other domesticated species, but also within , affecting hundreds of protein-coding genomic regions. A large number of inter-gene pool introgressions were identified. Furthermore, interspecific introgressions for disease resistance in breeding lines were mapped. Evaluation of newly developed single nucleotide polymorphism markers within previously discovered quantitative trait loci for common bacterial blight and angular leaf spot provides improved specificity to tag sources of resistance to these diseases. We expect that this dataset will provide a deeper molecular understanding of breeding germplasm and deliver molecular tools for germplasm development, aiming to increase the efficiency of bean breeding programs.

See: https://www.ncbi.nlm.nih.gov/pubmed/30025029

Figure 1: Variants discovery and diversity analysis. (A) Raw number of whole-genome sequencing (WGS) reads analyzed for each sample and the percentage of reads aligned to the reference genome (red line). The number of aligned reads corresponds to the bold segment of each bar. Reads from samples G35346 and G40001 were subjected to default and more sensitive alignment parameters in bowtie2 to increase the number of reads aligned to the reference. (B) Number of single nucleotide polymorphisms (SNPs) that could be reliably genotyped in each sample from a dataset of SNPs in nonrepetitive regions of the genome. Genotype calls are discriminated as homozygous for an alternative (nonreference) allele (blue), heterozygous or heterogeneous (red), and homozygous for the reference allele (gray). The percentage of nonreference genotype calls is displayed as a green line. (C) Neighbor-joining dendrogram of distances between the samples analyzed in this study based on genome-wide high-quality SNP markers.