Identification of a Candidate Locus and Development of a Molecular Marker for Male Sterility in Watermelon

초록

Genic male sterility (GMS) is an important trait for watermelon breeding programs to produce F1hybrids without the laborious steps of emasculation and hand pollination; however, the inheritanceof GMS and the underlying molecular mechanisms remain unclear. Here, we aimed to identify thecausal genomic region for GMS in watermelon and develop single nucleotide polymorphism (SNP)markers linked to the trait. Two inbred lines harboring a male sterility gene were crossed to generateF2 and near-isogenic line (NIL) populations for mapping loci and evaluating SNP markers. Ourstudy showed that the inheritance of GMS was controlled by a single recessive gene followingMendelian inheritance models in the segregation population. We applied bulked segregant analysis(BSA) and Illumina whole-genome resequencing (BSA-seq) to identify a candidate causal genomicregion for GMS at 8.9–13.0 Mb on chromosome (Chr.) 6. Next, we selected seven high-resolutionmelting (HRM) markers by retrieving 1-Mb genomic sequences around SNPs located within thecausal genomic region. The identified polymorphic SNPs were tested via HRM analysis in the F2population. By further narrowing the putative causal region, we identified a deleted and frameshiftedgene, Cla97C06G117840, at Chr. 6. As a result, we developed allele-specific PCR and HRMmarkers, which completely cosegregated with the male-sterility phenotype of the F2 and NILpopulations. Overall, our results will help effectively use GMS in watermelon breeding programsand accelerate the production process of F1 hybrids.

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