Identification of Causal Gene-Specific SNP Markers for the Development of Gynoecious Hybrids in Cucumber (Cucumis sativa L.) Using the PathoLogic Algorithm

Although the genome sequence of cucumber is publicly available, only a limited number of functional markers are in store for developing gynoecious hybrids using Indian genotypes. This study reported novel SNPs and InDels in the exonic regions of genes involved in gynoecy using two parents and their hybrid with genotyping-by-sequencing (GBS) by generating 3.547 Gb of raw data. Using NSDC reference genome GCA_000004075.2, a total of 40,143, 181,008 and 43,612 SNPs were identified, among which 514 were polymorphic between male and female parents but monomorphic between the male parent and the hybrid (confirming hybridity). We further identified that, out of those 514 SNPs, 74 were within the exonic regions of the sex-specific genes. The most interesting functional marker in this study was SNP 2,13,85,488, identified in the gene CsaV3_6G037780 G3I-38214 on chromosome 6, encoding 1-aminocyclopropane-1-carboxylate oxidase 1 (ACS1), which plays a key role in female flower production, as indicated in CuCyc with the PathoLogic algorithm. The InDel analysis also identified a variation inside the gene CsaV3_6G304050 G3I-37940, encoding histone lysine N-methyl transferase, involved in flowering and female gametophyte development. Thus, this study has identified gynoecy-specific functional markers; upon further validation, these markers will accelerate the evolution of gynoecious hybrids in India and global cucumber breeding programs.