Genetic Diversity and Molecular Markers of Cupped Oysters (Genera Crassostrea, Saccostrea, and Striostrea) in Thailand Revealed by Randomly Amplified Polymorphic DNA Analysis

Genetic diversity and species-diagnostic markers of 5 oysters in Thailand, Crassostrea belcheri (Sowerby, 1871), Crassostrea iredalei (Faustino, 1932), Saccostrea cucullata (Born, 1778), Saccostrea forskali (Gmelin, 1791), and Striostrea (Parastriostrea) mytiloides (Lamarck, 1819), were investigated by randomly amplified polymorphic DNA (RAPD) analysis. In a total, 135, 127, and 108 genotypes were observed from primers OPA09, OPB01, and OPB08 (Operon Technologies Inc., kits A and B), and 131 and 122 genotypes from primers UBC210 and UBC220 (University of British Columbia), respectively. Two hundred fifty-four reproducible and polymorphic fragments (200–2500 bp in length) were generated across the 5 investigated species. The average number of bands per primer varied between 12.4 and 32.2. The percentage of polymorphic bands within Crassostrea (53.23%–77.67%) was lower than that within Saccostrea and Striostrea oysters (86.21%–99.36%). Nine, species-specific markers were found in C. belcheri, 4 in C. iredalei, and 2 in S. cucullata. The mean of a ratio between the number of genotypes generated by each primer and the number of investigated specimens of C. belcheri (0.58) was lower than that of the remaining species (0.90–1.00). Genetic distances between pairs of oyster samples were between 0.105 and 0.811. A neighbor-joining tree indicated distant relationships between Crassostrea and Saccostrea oysters, but closer relationships were observed between the latter and Striostrea mytiloides. Received June 6, 2000; accepted September 12, 2000