Variations of Morphological Characters and Isozyme Patterns in Japanese Cultivars of Colocasia esculenta SCHOTT and C.gigantea HooK

Abstract

Morphological characters related to the vegetative organs, and peroxidase and esterase isozyme patterns were investigated for cluster analyses in 38 strains of taro and three of C.gigantea in Japan. Chromosome numbers of the strains were also determined. There were large variations in the morphological characters and the isozyme patterns among the taro strains. In contrast, few morphological variations and no zymographic variations were observed among the strains of C.gigantea. The small clusters based on the isozyme patterns corresponded more closely to the cultivar groups defined by KUMAZAWA et al. (1956) than those based on the morphological characters. Three strains were markedly distant from the clusters of their groups and they could have been included in the other cultivar groups. Diploid (2n=28) and triploid forms (2n=42) were found in taro, whereas only diploid ones (2n=28) in C.gigantea. These two forms could not be clearly separated by the method mentioned above. There are numerous discrepancies in the classification of the Japanese taro cultivars. KUMAZAWA et al. (1956) classified the largest number of strains based on the largest number of characters related to the morphology of the vegetative and flowering organs, on the texture of corms, and the chromosome number. In the present study, the classification by cluster analysis based on the isozyme patterns agreed well with that of KUMAZAWA's cultivar groups, unlike the classification based on the morphological characters. This finding suggests that KUMAZAWA's classification system for the cultivar groups is supported chemotaxonomically, and that cluster analysis based on two isozyme patterns is a suitable method for assigning the strains into the cultivar groups.