Mango genetic diversity analysis and pedigree inferences for Florida cultivars using microsatellite markers

Mango (Mangifera indica L.) germplasm can be classified by origin with the primary groups being cultivars selected from the centers of diversity for the species, India and Southeast Asia, and those selected in Florida and other tropical and subtropical locations. Accessions have also been classified by horticultural type: cultivars that produce monoembryonic seed vs. cultivars that produce polyembryonic seed. In this study we used 25 microsatellite loci to estimate genetic diversity among 203 unique mangos (M. indica), two M. griffithii Hook. f., and three M. odorata Griff. accessions maintained at the National Germplasm Repository and by Fairchild Tropical Botanic Garden in Miami, Fla. The 25 microsatellite loci had an average of 6.96 alleles per locus and an average polymorphism information content (PIC) value of 0.552 for the M. indica population. The total propagation error in the collection (i.e., plants that had been incorrectly labeled or grafted) was estimated to be 6.13%. When compared by origin, the Florida cultivars were more closely related to Indian than to Southeast Asian cultivars. Unbiased gene diversity (H-nb) of 0.600 and 0.582 was found for Indian and Southeast Asian cultivars, respectively, and both were higher than H-nb among Florida cultivars (0.538). When compared by horticultural type, H-nb was higher among the polyembryonic types (0.596) than in the monoembryonic types (0.571). Parentage analysis of the Florida cultivars; was accomplished using a multistage process based on introduction dates of cultivars into Florida and selection dates of Florida cultivars. In total, 64 Florida cultivars were evaluated over four generations. Microsatellite marker evidence suggests that as few as four Indian cultivars, and the land race known as 'Turpentine', were involved in the early cultivar selections. Florida may not represent a secondary center of diversity; however, the Florida group is a unique set of cultivars selected under similar conditions offering production stability in a wide range of environments.