Genetic Diversity and Microsatellite Alleles Associated with Fruits Taste in Chrysophyllum albidum G. Don from the Valley of Ouémé Phytodistrict, Benin

Abstract

Chrysophyllum albidum is a fruit tree species of great socioeconomic importance in West Africa, particularly in Benin, where its fruits are widely consumed. Despite its importance to local communities, the molecular determinants of fruit flavour remain unknown. This study aimed to elucidate the genetic basis associated with the taste of C. albidum fruits. Fruit trees spaced at least 50 metres apart were selected in the Valley of Ouémé phytodistrict, and three ripe fruits per tree were used for sensory evaluation by a panel of three trained, permanent tasters. Only trees whose fruit flavour was unanimously judged to match the flavour previously described by consumers or consenting owners were selected for the final sample. Molecular analysis was conducted on young leaves using 15 nuclear microsatellite markers. Heatmap analysis and Fisher's exact test were used to identify alleles associated with fruit flavour. At the end of the selection process, 30 trees were retained: 17 (56.67 %) produced sweet-tasting fruit and 13 (43.33 %) produced tart-tasting fruit. High genetic diversity was also observed (mean PIC = 0.673; mean expected and observed heterozygosities = 0.70 and 0.51, respectively; mean number of effective alleles = 4.36; rare-allele rate = 32.71 %). Two main genetic groups were identified, each containing the two taste types (sour and sweet) reported by consumers and unanimously confirmed by the tasting panel. The A3 allele of marker CGON51JQ036328 and the A11 allele of marker CGON21JQ036326 were associated with sour taste, whereas the A7 allele of marker CGON21JQ036326 was linked to sweet taste. The high genetic diversity still observed in C. albidum, despite the species' advanced vulnerability, confirms that it constitutes a valuable genetic resource meriting conservation; the preliminary associations established, in turn, provide a basis for subsequent functional and biochemical validation in larger, independent populations, as well as for varietal selection aimed at improving the organoleptic quality of the fruits.