Analysis of BAC-end sequences in common bean (Phaseolus vulgaris L.) towards the development and characterization of long motifs SSRs

Abstract

The increasing volume of genomic data on the Phaseolus vulgaris species have contributed to its importance as a model genetic species and positively affected the investigation of other legumes of scientific and economic value. To expand and gain a more in-depth knowledge of the common bean genome, the ends of a number of bacterial artificial chromosome (BAC) were sequenced, annotated and the presence of repetitive sequences was determined. In total, 52,270 BESs (BAC-end sequences), equivalent to 32 Mbp (~6 %) of the genome, were processed. In total, 3,789 BES-SSRs were identified, with a distribution of one SSR (simple sequence repeat) per 8.36 kbp and 2,000 were suitable for the development of SSRs, of which 194 were evaluated in low-resolution screening. From 40 BES-SSRs based on long motifs SSRs (≥trinucleotides) analyzed in high-resolution genotyping, 34 showed an equally good amplification for the Andean and for the Mesoamerican genepools, exhibiting an average gene diversity (HE) of 0.490 and 5.59 alleles/locus, of which six classified as Class I showed a HE ≥ 0.7. The PCoA and structure analysis allowed to discriminate the gene pools (K = 2, FST = 0.733). From the 52,270 BESs, 2 % corresponded to transcription factors and 3 % to transposable elements. Putative functions for 24,321 BESs were identified and for 19,363 were assigned functional categories (gene ontology). This study identified highly polymorphic BES-SSRs containing tri- to hexanucleotides motifs and bringing together relevant genetic characteristics useful for breeding programs. Additionally, the BESs were incorporated into the international genome-sequencing project for the common bean.