Abstract: In order to understand the genetic structure of wild Sargassum thunbergii populations along Dalian coast, an inter-simple sequence repeat (ISSR) analysis was made on the genetic diversity and genetic relationships of six geographic populations of S. thunbergii, including five populations DC, DT, JJ, SC and YC from Dalian coast and one population PL from Penglai. 160 ISSR loci tested, 145 (90.62%) were polymorphic with 14 different ISSR primers. The values of percentage of polymorphic bands (PPB), Shannon’s index (I), and Nei’s gene diversity (H) were 41.25%-64.38%, 0.2321-0.3464, and 0.1585-0.2333, respectively. Dalian populations had higher genetic diversity than Penglai population. The analysis of molecular variance (AMOVA) showed that in the total genetic variation, the variation within populations was 35.66%, and the variation among populations was 64.34%. The value of gene flow (N_m) among the six populations was 0.7837, suggesting a limited gene flow among the populations. The UPGMA tree based on Nei’s genetic identity showed that population DC was clustered with populations DT and JJ, then with populations SC and YC, and finally with PL. All the results suggested that different reproductive mode and different growth environment might have critical roles in the genetic differentiation of S. thunbergii populations.

Key words: Artificial neural network, Genetic algorithm, Water stress, Root length density distribution, Prediction