Male‐specific DNA markers provide genetic evidence of an XY chromosome system, a recombination arrest and allow the tracing of paternal lineages in date palm

Abstract

SummaryWhether sex chromosomes are differentiated is an important aspect of our knowledge of dioecious plants, such as date palm (Phoenix dactylifera). In this crop plant, the female individuals produce dates, and are thus the more valuable sex. However, there is no way to identify the sex of date palm plants before reproductive age, and the sex-determining mechanism is still unclear.To identify sex-linked microsatellite markers, we surveyed a set of 52 male and 55 female genotypes representing the geographical diversity of the species.We found three genetically linked loci that are heterozygous only in males. Male-specific alleles allowed us to identify the gender in 100% of individuals. These results confirm the existence of an XY chromosomal system with a nonrecombining XY-like region in the date palm genome. The distribution of Y haplotypes in western and eastern haplogroups allowed us to trace two male ancestral paternal lineages that account for all known Y diversity in date palm.The very low diversity associated with Y haplotypes is consistent with clonal paternal transmission of a nonrecombining male-determining region. Our results establish the date palm as a biological model with one of the most ancient sex chromosomes in flowering plants.

Genetic diversity analysis of date palm (Phoenix dactylifera L.) in the Kutch<br>region of India using RAPD and ISSR markers

“…Similarly, 3 female specific markers were identified in date palm by Younis et al (2008). Male specific alleles were identified by Cherif et al (2012) in 52 male genotypes of date palm using microsatellite markers. They found three genetically linked loci which were heterozygous only in males.…”

Synthesis and assessment of date palm genetic diversity studies

“…The oases agroecosystems, perfectly adapted to the specific constraints of the environment, is largely shaped by the genetic diversity of the date palm. Cherif et al (2013) reported on male-and female-specific DNA markers and presented secondary statistics including number of alleles (A), H o , H e and F is (Table 4). Significant differences were found between FA (0.468) and MS (1.00) for Ho and between MS (-0.304) and each of MA (-0.012), and FA (-0007) for F is .…”

“…The difference between the magnitude of the r-values between Ne and each of Fis and PPL is worth further exploration in date palm. The observed heterozygosity estimates reported by Cherif et al (2013) on male-and female-specific DNA markers included secondary statistics on the fixation index of all four combinations of male and female autosomal and sex chromosomes. The relationships based on these four combinations were used to estimate Fis as a function of Ho, and plot the distribution of the four loci combinations (Figure 7).…”

Novel Set of Sex-Specific PCR-Based Markers Reveals New Hypothesis of Sex Differentiation in Date Palm

“…They identified two SCoT and four RAPD sex-specific markers. While, [12] employed the microsatellites marker system for the first time to identify three male-specific SSR markers tested on date palm genotypes collected from different geographic origin (Tunisia, Morocco, Italy, Djibouti, Oman, Syria and Iraq) with clearly ignoring for Egyptian genotypes (which produce about 20% of global dates). While, [11] identified male-linked markers, but this markers still requires confirmation, as the markers were validated only in a small sample and with an unsatisfactory accuracy of 90% [12].…”

“…This studies included the uses of isozymes [7], peroxydases [8], molecular marker tool such random amplified polymorphic DNA (RAPD) [9,10], PCR-based restriction fragment length polymorphism (PCR-RFLP) approach [11], microsatellites [12], and recently; PCR-based approaches (RAPD and SCoT) [13].…”