2010 Volume 60 Issue 3 Pages 195-202
Genetic variability and its spatial structure within and among Japanese populations of wild radish Raphanus sativus L. var. hortensis Backer f. raphanistroides Makino were surveyed at regional (<250 km) and local (<3.5 km) scales using eight microsatellite markers. A regional-scale survey was performed on seven populations from sandy coasts of the Sea of Japan. For local-scale survey, 10 subpopulations were sampled along the sandy seashore of Kumihama coast. The level of genetic variability was similar between regional (HT = 0.577) and local (HT = 0.604) samples. Local populations and subpopulations showed heterozygote deficiency as expressed by average inbreeding coefficient values of 0.206 and 0.179, respectively. The level of genetic differentiation among populations was low, with fixation index values of 0.048 and 0.034 for regional and local scales, respectively. Nonetheless, analysis of molecular variance showed significant genetic differentiation among populations/subpopulations. Spatial genetic analysis indicated a positive correlation between pairwise values of spatial distance and genetic differentiation both at regional and local levels. These results suggest that the wild radish populations surveyed are genetically structured and each population retains a unique genetic composition. Genetic heterogeneity among local populations provides the opportunity to obtain genetic resources with various useful traits by extensive exploration of different populations.
