植栽年代の異なるクヌギ人工林の遺伝的組成 : 大陸産種苗植栽の可能性植栽年代の異なるクヌギ人工林の遺伝的組成 : 大陸産種苗植栽の可能性AN00162451 Genetic composition of Quercus acutissima stands between two planted ages in Japan : Possibility of usage of seeds from the Continent
The number of Quercus acutissima plantations increased after the 1960s due to rising demand for logs for shiitake mushroom cultivation. To clarify the genetic differences among stands before and after the 1960s, we analyzed six old plantations and 13 mature plantations in Shizuoka, Yamaguchi, and Oita, one population in Korea, and two continental populations in China, (a total of 990 individuals), using seven nuclear microsatellite markers and six chloroplast microsatellite markers. The genetic diversity of nuclear DNA was high in Chinese populations and no clear differences were detected between old and mature plantations in Japan. The results of STRUCTURE analysis showed three genetic clusters, one each for the Chinese populations and Japanese plantations and the Korean populations were an admixture of the other two clusters. Sixteen chloroplast haplotypes were detected and one specific haplotype dominated all Japanese plantations; however, its frequency was low among continental populations. The proportions of plantations in which the frequency of the dominant haplotype exceeded 90% for old and mature plantations respectively, were 4/5 in Shizuoka, all 3 in Yamaguchi, and 4/11 in Oita. The neighbor-joining dendrogram showed two clades, one for Japanese populations and the other for continental populations, with several Japanese plantations between the two clades. Holotypic diversity was higher in mature plantations than in old ones. The genetic characters of Q. acutissima plantations in Japan changed after the 1960s, perhaps due to the influence of Korean seeds and seedlings.