臺灣常見杜鵑花(Rhododendron spp.)栽培品種之葉部形態調查及遺傳歧異性分析

Abstract

Abstract In this study, we study on morphological variation and genetic diversity of 41 Rhododendron cultivars in Taiwan. During the analysis, We hope to establishment a rapid and accurate detection method. We also hope to use the molecular markers to analyze the relationships among 41 Rhododendron cultivars in Taiwan. We can usually see the 4 major groups of Rhododendron in Taiwan, they are Hirado azalea cultivars, Satsuki cultivars, Kurume azalea cultivars and Rhododendron native in Taiwan. In the past, most taxonomy work was based on morphological description, but lack in systematic investigation. In this study, we recorded the flower and leaf shapes by digital camera, together with leaf morphological analysis of the 4 major groups of Rhododendron in Taiwan. In view of morphological characteristics, leaf length, leaf mid width and leaf stalk ( petiole ) length can distinguish Hirado azalea cultivars, Satsuki cultivars and Kurume azalea cultivars into two groups, the one is Hirado azalea cultivars and the second group is Satsuki cultivars and Kurume azalea cultivars. Leaf morphological characteristics of Satsuki cultivars and Kurume azalea cultivars are very similar. We can distinguish between Satsuki cultivars and Kurume azalea cultivars and determined by the two axes on the basis of leaf mid width and leaf length/leaf mid width. We can usually distinguish between Hirado azalea cultivars, Satsuki cultivars, Kurume azalea cultivars and Rhododendron native in Taiwan by their leaves—the leaf of Rhododendron native in Taiwan are different from others. The leaf average length of Rhododendron native in Taiwan are between Satsuki cultivars and Kurume azalea cultivars. In this study, the pictures of flower records can be used as reference resources to distinguish the cultivars. The varieties ( lines ) of Rhododendron were not clearly classified in Taiwan. The objective of this study was to identify the genetic relationship among the 41 Rhododendron cultivars through numerical analysis of the leaf characters. Using cluster analysis of the 11 leaf characters, 41 cultivars were divided into six main groups. The ordination pattern of the principal component analysis was similar to the grouping pattern of the cluster analysis, and the first two principal components derived the principal component analysis explained 78.93% of the observed variation. The first group(Ⅰ) included Hirado azalea cultivars. Cultivars in the second group (Ⅱ) were Rhododendron kanehirai. The third group (Ⅲ) were Satsuki cultivars. The fourth group (Ⅳ) were Kurume azalea cultivars. The fifth group (Ⅴ) were Rhododendron oldhamii. The sixth group (Ⅵ) hybrid strains. A total of 41 cultivars of Rhododendron were evaluated by using random amplified polymorphic DNA ( RAPD ) marker. Objectives were to evaluate genetic distance within those 41 cultivars. Screening from 18 primers and 42 polymorphic DNA fragment were derived from 7 primers. A dendrogram generated by UPGMA ( unweighted pair-group method with arithmetic mean ) clusteranalysis. The results also show the similar varieties were cluster into the same subgroup. Similarity indexes among 41 cultivars were extremely from 0.36 to 1. The number 7, 9, 11 of Hirado azalea cultivars had 100% similarity indexes, indicating the closest relationship. Otherwise, the number 18 of Satsuki cultivars having 36% similarity indexes showed the farthest genetic relationship with other tested Rhododendron cultivars. In brief, that the RAPD markers is an effectively and reliably method for analysis of the genetic distance of Rhododendron cultivars. The entire internal transcribed spacer ( ITS ) region between 18S and 26S ribosomal RNA ( rRNA ) genes among 13 Rhododendron accessions in Taiwan were amplified by polymerase chain reaction ( PCR ). The primers of PCR, IT1: 5’-TCGTAACAAGGTTTCCGTAGGT-3’ and IT2: 5’-GTAAGTTTCTTCTCCTCCGCT-3’ were designed for amplification. Genetic relationship of 13 Rhododendron accessions in Taiwan was derived from the sequence analysis of the internal transcribed spacer ( ITS ) region of ribosomal DNA. Sequences of complete ITS region, including ITS1, 5.8S rDNA, and ITS2, were obtained by direct sequencing of polymerase chain reaction ( PCR ) amplified fragments. Aligned sequences of ITS1 and ITS2 , we found the ITS1 region contained 3 variable sites and the ITS2 region contained 6 variable sites. A distance matrix of sequence divergence was caculated using Kimura’s two parameter model. Divergene values among the accessions were extremely low ranging from 0.00 to 0.609%. A dendrogram generated by UPGMA ( unweighted pair-group method with arithmetic mean ) cluster analysis. According to the dendrogram, 1 main cluster were generated among 13 Rhododendron accessions in Taiwan.