Genetic Mapping of Gynoecy in Momordica charantia Using RAD-seq Analysis

Bitter melon (Momordica charantia) is a monoecious cucurbitaceous species, which is mainly grown from east to south Asia.  For its commercial production of F1 cultivars, we employed its gynoecious line  (OHB61-5) as a maternal parent. In order to identify this gynoecious gene in OHB61-5, we carried out genetic mapping by Restriction-Associated DNA tag sequence (RAD-seq) analysis.  OHB61-5 was crossed with a monoecious line (OHB95-1A), and male: female ratio was scored in its F1 and F2 plants. According to segregation of gynoecy and monoecy in F2 population, gynoecy was determined by a single recessive gene.  From RAD-seq analysis using PacI and AseI, polymorphisms between parental lines could be identified as specific tags in either parent. Subsequently, genomic DNA from segregated F2 plants were similarly applied to RAD-seq analysis for exploring tags closely linked to the gynoecious locus.  Several tags, carrying SNPs between the parents, showed linkage to the gynoecious locus. SNP in each tag was genotyped in individual F2 plant and its genetic distance was estimated to the target locus.  The present results demonstrated that RAD-seq analysis facilitated to genetic mapping of desired traits without previously known genome sequence, markers or linkage map.