PAPAYA GENETIC DIVERSITY ASSESSED WITH MICROSATELLITE MARKERS IN GERMPLASM FROM THE CARIBBEAN REGION

Papaya genetic diversity was investigated in a sample of 72 accessions from 13 geographic origins, including Costa Rica (wild and cultivated materials), Colombia, Venezuela, and Antillean islands, using 15 microsatellite markers, computing allelic richness and frequency, expected heterozygosity (He) and genetic distances, and performing a principal coordinate analysis (PCO). A total of 99 alleles were identified. The samples from Guadeloupe, Venezuela, Colombia and Barbados showed the highest diversity, with He values between 0.69 and 0.50, contrasting with those of Costa Rica (He values of 0.37 and 0.44). On the other hand, this country shows the highest number of specific alleles. In the PCO principal plan, genotypes cluster according to their geographic origin, with few exceptions. This structure and the genetic distances between samples show correspondence with geographic distances among Costa Rica, Colombia, Venezuela and Guadeloupe, but not with those among the Antillean islands. The two natural populations of Costa Rica show differentiation neither between the Caribbean Coast and the Pacific Coast nor between wild and cultivated genotypes. As expected, microsatellite markers revealed more polymorphism in papaya than AFLPs or RAPDs. The results obtained with this powerful tool lead to renew efforts of characterization and conservation of American papaya germplasm. (Resume d'auteur)