A taxonomic study of the genus Rhizopus by isozyme patterns
Liou, Guey-Yuh; Chen, Chien-Cho; Yuan, Gwo-Fang; Chien, Chiu-Yuan
Isozyme patterns of esterase, malate dehydrogenase, hexokinase, glucose-6-phosphate dehydrogenase, 6-phosphate-gluconate dehydrogenase, phosphoglucose isomerase, and fumarase were used in this study to classify 61 selected strains of Rhizopus by polyacrylamide gel electrophoresis. The specific patterns of esterase manifested the intraspecific variation between the strains of Rhizopus. The electromorph of esterase had to be excluded from this study because of its extraordinary complexity. Cluster analysis of 61 selected strains using patterns of six other enzymes yielded a dendrogram with two clusters (cluster I had two subclusters). In the dendrogram, three distinct groups, the same as those obtained by traditional methods, are recognizable: R. stolonifer-group, R. oryzae-group, and R. microsporus-group. On the other hand, a number of specific taxonomic problems were addressed. Rhizopus azygosporus and R. homothallicus were grouped within the strains of R. microsporus. Rhizopus stolonifer var. reflexus is rather divergent from R. stolonifer var. stolonifer, and R. oryzae turned out a heterogeneous species. The results indicate that isozyme analysis can be effective in reevaluating the taxonomy of the genus Rhizopus.