Genetic diversity of Calycanthaceae accessions estimated using AFLP markers

In Calycanthaceae, all species are attractive flowering shrubs bearing high ornamental value. Especially, Chimonanthus praecox is a famous traditional fragrant flower plant in China. It has been extensively cultivated for over one thousand years and also appreciated as potted landscapes and cut flowers. In this project, silver-stained amplified fragment length polymorphism (AFLP) was applied to detect the genetic relationships among 83 Calycanthaccae accessions, including 76 genotypes from C. praecox and 7 accessions from the other species. Eight primer combinations yielded a total of 387 polymorphic bands, with an average of 48.4 per assay. The results obtained with the analysis of genetic similarities among accessions according to Jaccard's similarity coefficient and the clusters constructed based on the UPGMA indicated that: (1) Chimonanthus zhejiangensis was highly differentiated from the other species and detected the closest relationship with C. salicifolius, which possibly supported that C. zhejiangensis was a distinct species rather than the synonym of C. nitens. Besides, C. praecox was much more closely related with Chimonanthus campanulatus than the other species. (2) Extensive genetic differentiation existed among C. praecox genotypes. The Jaccard's similarity coefficient among the accessions ranged from 0.70 to 0.96, and 76 accessions were divided into seven main groups based on the UPGMA dendrogram. The genotypes from two different areas were clustered, respectively, suggesting genetic divergence between the two local cultivated populations. However, the clusters did not match well with the floral morphological characters, perhaps conforming that the floral phenotypic characters (flower type and size, medium and inner tepal color, and medium tepal shape) of C. praecox were quantitative traits controlled by multi-genes rather than qualitative traits. In addition, the results also demonstrated AFLP markers were useful for evaluating the genetic relationship among species in Calycanthaceae and the genetic variation of C. praecox genotypes, and may serve as efficient fingerprinting technique for further identification and classification of germplasms. (c) 2006 Elsevier B.V. All rights reserved.