A Semi-Quantitative Bulked Segregant Analysis Preliminarily Localizes a Maize Male-Sterility Gene

Bulked segregant analysis (BSA) assists in map-based cloning of mutant genes.However, a traditional BSA requires many high-density markers for successful linkage analysis which is labor-intensive and time-consuming.In this study, a semiquantitative DNA analysis program was optimized and combined it with BSA, resulting in a semi-quantitative BSA (sq-BSA).The sq-BSA approach allowed evaluation of the proportions of marker-defined individuals (dominant or recessive marker types) in bulks.The sq-BSA method was used to map a male-sterility (ms) gene, ms2016, in maize.Forty polymorphic markers were screened from one-third of each chromosome (from the head or tail) for mapping.Among these markers, seven were identified as candidate gene-linked markers, of which four markers (bnlg1046, umc1563, umc1171 and umc1722) were located on chromosome 5.Using group validation, ms2016 was anchored on chromosome 5 and was most closely linked to bnlg1046.Furthermore, four new InDel markers located near bnlg1046 were screened to map the preliminary location of ms2016.The ms2016 gene was mapped to an 8.7 Mb interval flanked by the InDel polymorphic markers I5-3 (chr5:14588060) and I5-12 (chr5:23308445).Thus, this improved BSA method (sq-BSA) requires only a small number of molecular markers to quickly localize a target gene, representing a high-efficiency tool for mutant gene mapping.