Chloroplast DNA variability in Japanese and Korean populations of wild radishes Raphanus sativus var. hortensis f. raphanistroides (Brassicaceae)

Genetic variability within and among wild radish populations in Japan and Korea was investigated using a PCR-RFLP-based examination of chloroplast DNA (cpDNA) regions. A total of 319 individuals from seven Japanese populations and one Korean population were surveyed. PCR-RFLP analyses of three regions (a total of 4.0 kb) using 94 individuals from four populations revealed three cpDNA haplotypes. Because the three haplotypes were distinguishable by the restriction pattern generated following digestion of the psaA-ycf3 region with DdeI, only the psaA-ycf3 region of the remaining samples was surveyed. Seven out of the eight investigated populations were polymorphic in this region and four populations contained all three of the haplotypes. Gene diversity for all of the samples was 0.567, and diversity values within single populations ranged from zero to 0.665 with an average of 0.345. The coefficient of gene differentiation among the populations was 0.392, which is higher than estimates made using allozymes and morphological genes. The pollen-to-seed flow ratio was estimated to be 1.142. This result indicates that differences between the dispersal distances of pollen and seeds did not cause the higher level of genetic differentiation in the cpDNA. Rather, genetic differentiation in the cpDNA may have been caused by the smaller effective population size of the maternally inherited organellar genome.