Comparative estimates of genetic divergence in dahlia

摘要

The performance of 18 dahlia varieties was evaluated for 36 metric characters in RBD with five replications during 1998-99 winter to assess genetic divergence among them through multivariate analysis following Mahalanobis' D~2 statistic, canonical analysis and numerical taxonomic approach. Analysis of variance showed significant differences among the test entries for all the characters except bloomlife of flower and tuber number per plant. Based on 36 characters, the genotypes were grouped into six clusters following D2 analysis where three single-variety clusters were distinguished for their high number of small flowers as compared to three multi-variety clusters possessing less number of large sized flowers. This classification was in broad agreement with the two-dimensional representation of the entries using the first two canonical vectors. The characters having major contribution to genetic divergence were stalk diameter of secondary flower, number of ray florets in main flower, petal length and number of ray florets in secondary flower in order of merits. In numerical taxonomic approach, the dendrogram showing clusters at appropriate phenon levels indicated that the entries were broadly classified into four clusters at 70 and 75% phenon levels, they were grouped into nine clusters. Although there was 66.7% correspondence between dendrogram clustering at 70% phenon and D~2 clustering, the subtle differences between genotypes in a cluster could further be assessed through dendrogram clustering at 75 and 80% phenon levels. Late flowering genotypes Croydon Monarch Red, Thelma Davidson, Kenya White, Kenya Gerua and Kenya Bicolor with less number of large sized flowers and short ornamental crop duration in one hand and early flowering, GloriosaSamalatal with more number of small flowers and longer ornamental crop duration on the other hand were identified as distinct types for direct use as commercial varieties and at the same time for use as parents in developing commercial hybrids by combining desirable features from both the types.