Identification of a male-specific region (MSR) in Spinacia oleracea

Dioecy, the presence of male and female individual, has evolved independently from hermaphroditism in multiple flowering plant lineages. Spinach, an important leafy vegetable crop worldwide, is a dioecious species with an XY sex-determination system. Although some markers that are fully linked to male-determination locus were identified, the male-specific region (MSR) remained unclear. In this research, five male individuals and five female lines were resequenced to identify the male-specific region. We identified a region (∼21 kb) on chromosome 4 (putative sex chromosome) where the five females had a low reads coverage, while the five males had high coverage. A KASP marker, SponR, developed from a single nucleotide polymorphism (SNP) closely linked to the MSR was co-segregating with the sex determination gene in the population of 958 individuals, suggesting that the MSR might be specifically present in male spinach plants.