Development of Female (F) Locus Specific Co-Dominant Marker from Cucumber

Cucumber is a typical monoecious plant with individual male and female flowers, and sex expression in cucumber is mainly determined by three major genes: F/f, M/m and A/a. Gynoecy plays an important role in cucumber hybrid breeding and use of gynoecious lines as maternal parent ensures high productivity. This study aimed to identify a co-dominant molecular marker linked to Female (F) locus to distinguish homozygous and heterozygous gynoecious lines for cucumber breeding. Firstly, we analyzed the sequence polymorphism of 5 gynoecious and 5 monoecious inbred lines to detect the polymorphism linked to F locus. A pair of specific primer based on insertion/deletion polymorphism on 3’ UTR of branched-chain amino acid transaminase (BCAT) gene was designed to examine the polymorphism in the parents, F₁ and F₂ segregating population and additional 56 divergent cucumber accessions. The result showed that the specific fragment amplified with Cs-BCAT-F/Cs-BCAT-R, was identified as a co-dominant marker and almost co-segregated with sexual phenotype in F₂ population. Furthermore, we present a new intensive linkage map for F locus using Indel markers. This is the first report for the development of F locus specific co-dominant marker which can distinguish homozygous and heterozygous gynoecious and it could be used in marker-assisted selection in cucumber breeding.