A study of selected species of Rosa using isozyme polymorphisms

Abstract

The genus Rosa has a wide distribution and a large number of variable species. It has more than 100 species classified into four subgenera. Three of the subgenera are monotypic. The species in the subgenus Rosa are classified into 11 sections. Forty seven Rosa species (116 total accessions) from subgenera Rosa and Platyrhodon were characterized for isozyme phenotypes using starch gel electrophoresis. Four enzymes (ACP, MDH, PGI, and 6PGD) were evaluated using three electrode buffer systems. Isozyme phenotypes were used to analyze the phylogenetic relationships among the selected Rosa species. Traditional taxonomy and crossing behavior were also used in evaluation of the isozyme data. Principal components and cluster analyses suggest that isozyme data can be applied to the classification of Rosa species at the section level. Cluster analysis was conducted at both the sectional and species levels. Three different methods of cluster analysis were performed for sectional level. Two of these cluster analyses had almost identical clustering, but the other showed differences in clustering sections. The cluster analysis method which explained the most variability for the first three eigenvalues was selected in performing cluster analysis at the species level. The clustering of Rosa using isozyme data generally supports the traditional classifications. Five Asian rose sections Synstylae, Pimpinellifoliae, Laevigatae, Banksianae, and Chinenses were more closely grouped than the North American and European roses. Section Cassiorhodon and Synstylae which have the most species and the widest distribution showed highly polymorphic isozyme phenotypes. Isozyme data indicates that the sections Cassiorhodon and Carolinae should be combined and that the subgenus Platyrhodon should not be classified as a separate subgenus, but rather as another section within the subgenus Rosa along with sections Bracteatae and Cassiorhodon.