Intra-Specific Ploidy Variations in Cultivated Chinese Yam (Dioscorea polystachya Turcz.)

抄録

Chinese yam (Dioscorea polystachya Turcz.) is an edible tuber crop cultivated mainly in temperate regions of Japan and China. Chinese yam cultivars in Japan are classified into the following three groups: Nagaimo, Tsukuneimo, and Ichoimo, which produce cylindrical, round, and flattened tubers, respectively. In the present study, the chromosome numbers of cultivated Chinese yams from Japan were estimated. The chromosomes of the cultivar ‘Kagamaruimo’ were observed, and the chromosome number was estimated to be 2n = approximately 100. Flow cytometry using ‘Kagamaruimo’ as an internal reference standard revealed that the number of chromosomes in the 11 cultivars belonging to the Nagaimo group was 2n = approximately 140, while in the remaining 10 cultivars classified in the Tsukuneimo or Ichoimo group, the chromosome number was 2n = approximately 100. Based on data from shape analysis of leaves, Chinese yam cultivars could be divided mainly into two groups: a group that includes cultivars of Nagaimo and a group that includes cultivars of Tsukuneimo and Ichoimo. A high correlation was also found between stomatal traits and chromosome number. Based on the length, width, and size of the stoma, chinese yam cultivars were divided into two groups: cultivars with the chromosome number 2n = 100 and those with 2n = 140. Based on the results obtained in the present study, chinese yam cultivars can be divided into two genetic groups: a group containing cultivars of Nagaimo and a group containing cultivars of ‘Tsukuneimo’ and ‘Ichoimo’.