QUANTIFICATION AND CHARACTERIZATION OF NUCLEAR GENOMES IN COMMERCIAL RED SEAWEEDS (GRACILARIALES) FROM THE PHILIPPINES

Eight species of Gracilariaceae from the Philippines, representing the genera Gracilaria, Gracilariopsis and Hydropuntia, were investigated to quantify and characterize their nuclear genomes. DNA reassociation kinetics were used to determine nuclear genome organization and comple xity in six of these species. Results indicate the presence of three s econd order components corresponding to fast, intermediate and slow fr actions. Repetitive sequences varied from 13-74% and unique DNA ranged from 26-84%. Microspectrophotometry with the DNA-localizing fluorochr ome DAPI was used to quantify nuclear DNA contents. Comparisons of mea n nuclear DNA (I-f) values to chicken erythrocytes (RBC) resulted in a n estimate of 0.38-0.43 pg/2 C genomes for seven of the species invest igated. Preliminary analyses of agar content and quality confirm the e conomic potential of Gracilaria firma, Gracilaria sp. 2 from Sorsogon and Gracilariopsis bailinae. Nuclear genome profiles developed from da ta for genome size, organization and complexity are compared with data for agar quantity and quality. Gel quality and quantity do not appear to be correlated with either large repetitive fraction DNA or a high degree of genome complexity.