关键词: 传统菊花, 表型性状, 核心种质, 取样策略, 评价参数

Abstract:

【Objective】Exploring the optimal sampling method of constructing the core collection of traditional chrysanthemum varieties and the resulted core collection would help to facilitate the collection and preservation of traditional chrysanthemum germplasm resources.【Method】A collection of 2 249 traditional chrysanthemum germplasm resources, recorded in the monograph “Chinese Chrysanthemum”, were divided into eight groups according to ligulate floret color. Sixteen alternative core collections, resulted from stepwise clustering method of four overall sampling scale (5%, 10%, 15%, and 20%) and four group sampling ratio (simple ratio, logarithmic ratio, square root ratio, and diversity ratio), were compared to find the best sampling strategy for constructing core collection of traditional chrysanthemum. Consequently, the construction effects of two intra-group sampling methods (cluster and random) were further studied. The representativeness of the core collection established under the optimal method was comprehensively tested by both multiple characteristic values (minimum, maximum, mean, standard deviation, coefficient of variation, and diversity index) and evaluation parameters (percentage of mean difference, percentage of variance difference, range coincidence rate, variable rate of coefficient of variation, and phenotypic retention ratio). 【Result】According to flower color, each group showed a normal distribution, ensuring the uniformity of sampling; Both logarithmic ratio method and diversity ratio method could make the sampling number of each group more balanced, and had a corrective effect. The parameter values of the core collection constructed under the logarithmic ratio method reached the maximum, showing the optimal sampling ratio method. With the increase of the overall sampling size, the genetic diversity index showed a trend of increasing first and then decreasing, the variation rate of coefficient of variation continued decreasing, and the range of coincidence rate and phenotypic retention ratio continued increasing. When the sampling size was greater than 10%, the genetic diversity index and the variation rate of coefficient of variation decreased, while the range coincidence rate and phenotypic retention ratio increased slightly, it was concluded that the most suitable overall sampling size was 10%. The parameter values of the alternative core collection constructed by cluster sampling were larger than those by random sampling, indicating the better richness and uniformity of core collection by the cluster sampling method. The eigenvalues of the core collection were consistent with those of the original collection, and the several evaluation parameters showed the expected uniformity and abundance of the core collection, reflecting the phenotypic diversity. By supplementing the “chasing hug” trait lost by clustering and improving the two traits of inflorescence height and outer petal length, the core collection of 228 traditional chrysanthemum varieties was finally constructed, accounting for 10.14% of the original materials.【Conclusion】Based on 15 phenotypic traits of 2 249 traditional chrysanthemum varieties, the best core collection construction method was determined after systematic comparison of alternative core collections constructed by various overall sampling size, sampling ratio method and sampling method in the group, and the representativeness of the core collection was analyzed and verified. The eigenvalues and evaluation parameters showed that the core collection constructed in this study was effective and capable of representing the genetic diversity of the original traditional chrysanthemum collection.

Key words: traditional chrysanthemum, phenotypic traits, core collection, sampling strategy, evaluation parameter