Development of a molecular maker for sex identification in Thai commercial date palm (Phoenix dactylifera L.)

Date palm (Phoenix dactylifera L.) is a dioecious plant, with male and female plants having distinct characteristics. Female plants are responsible for fruit production, and only approximately 10% of male plants are necessary for effective pollination. The determination of plant sex occurs during the first flowering, a process that typically spans 3-7 years. However, this extended timeframe results in significant time and valuable plantation resources being expended in the maintenance of trees. To address this issue, the study focused on sex identification of date palms using DNA markers. The research aimed to develop sex-specific markers for certain date palm cultivars, employing the high annealing temperature random amplified polymorphic DNA (HAT-RAPD) technique for accurate and reliable sex identification. In this investigation, 45 RAPD primers underwent screening in both male and female date palm plants to pinpoint sex-specific markers. Out of the total primers tested, only one, OPW-18, exhibited a correlation with sex. OPW-18 produced a distinct band of approximately 400 bp, consistently present in all male plants but absent in all female plants. The male-specific fragment from OPW-18 was cloned and sequenced to facilitate the development of sex-specific sequence-characterized amplified region (SCAR) primers. The outcomes revealed that the newly crafted SCAR primer pair, mspW18-2F and mspW18-2R, successfully amplified a unique fragment of 283 bp exclusively in male plants. This capability allowed the identification of 100% of male plants in the KL1 and Barhi cultivars. These markers prove to be efficient, reliable, and reproducible for early-stage sex identification in plants.