Fine mapping of a novel male-sterile mutant showing wrinkled-leaf in sesame by BSA-Seq technology

Abstract

Genic male sterility (GMS) is a very important approach of heterosis exploitation in sesame (Sesamum indicum L.). Visible marker-trait linked to GMS is necessary since it can facilitate the breeding of new GMS lines and the production of F1 hybrid seeds. We have successfully developed such a GMS line showing wrinkled-leaf (JQA) from a mutant identified in a multiple-cross population in sesame. However, the underlying genetic basis for this JQA line is unclear. To understand the inheritance patterns, near-isogenic line (NIL) together with F2 and BC1 populations segregating for both pollen-fertility and leaf-shape was constructed. Morphology investigation indicated that the JQA line was controlled by a single recessive gene, Sims5. By combining bulk-segregant analysis and next-generation sequencing technology (BSA-Seq) in the NIL population, seven and four chromosome regions putatively associated with traits variation were identified by SNP and InDel markers, respectively. A 1,817.6-kb consensus region on chromosome 12 was obtained by intersecting these intervals, which was most likely the target region containing the candidate gene(s) responsible for pollen-fertility and leaf-shape. The consensus region was further narrowed down to only 219.7 kb by fine mapping in a BC1 population using SSR and InDel markers. Real-Time qRT-PCR analysis of genes within this region showed that four (XM_011097706.2, XM_011097714.2, XM_020698411.1 and XM_011097719.2) and one (XM_020698321.1) genes were highly suppressed in the anther and leaf of mutant plant, respectively, suggesting their important role in pollen and leaf development. These findings not only lay a solid foundation for the isolation and functional analysis of genes for pollen-fertility and wrinkled-leaf but also provided valuable genetic resources and molecular markers for the breeding of new sesame hybrid varieties.