Characterization of a sex-determining locus and development of early molecular assays in Telfairia occidentalis, a dioecious cucurbit

Abstract Although there exist over 7’000 crop species, only a few are commercially valuable and grown on a large scale in monocultures worldwide. However, underutilised crops (also called orphan crops) have great potential for food security and Telfairia occidentalis (Cucurbitaceae) is one such orphan crop grown in West Africa for its nutritious leaves and oil and protein-rich seeds. In this dioecious crop, farmers like to eliminate male plants and mostly keep females to increase their yield but face the challenge of determining sex with limited morphological differences between females and males before flowering. This study used double digested restriction site-associated DNA sequencing data (ddRADseq) to examine the genetic diversity within and among landraces of T. occidentalis, identify common sex-determining loci, and establish reliable assays to characterize the sex of immature plants in the vegetative state. Two molecular assays for distinguishing males from females of T. occidentalis were thereupon developed based on polymerase chain reaction (PCR) to genotype sex-specific sequence variation either through restriction by Mfe1 or the direct use of sex-specific primers. Both assays require standard laboratory conditions to reach a certainty of 94.3% for females and 95.7% for males from studied samples. With the inclusion of additional landraces, medium to large scale farms growing T. occidentalis as a crop can readily benefit from an early determination of the sex of plants.