关键词: 宽皮柑橘, 表型鉴定, 遗传多样性, 重测序, 系统进化

Abstract:

【Objective】 In this study, the whole-genome resequencing data and phenotypic identification information were used to reveal the genetic variation and population structure of mandarin germplasm resources and to explore elite citrus germplasms with these information, the aim was to promote citrus variety improvement in the direction of high fruit quality and diversification. 【Method】 In 2021 and 2022, 25 phenotypic traits of fruits and flowers of 473 mandarin accessions were identified in two consecutive years, and the young leaves were collected for DNA extraction, library construction and sequencing. Diversity analysis of phenotypic information was carried out using the variation coefficient and Shannon-Wiener index. To screen out excellent mandarin germplasm, a comprehensive evaluation on mandarin germplasm resources was conducted using correlation analysis, cluster analysis, and principal component analysis. Phylogenetic tree analysis was performed based on resequencing data to analyze the characteristics of the group to which the excellent germplasm belongs. 【Result】 There are extensive variations and rich genetic diversity in 473 mandarin accessions. The variation coefficient of 21 quantitative traits ranges from 9.36% to 76.98%, with an average of 34.95%. and the genetic diversity index from 1.71 to 2.08, with an average of 1.93. The diversity index of the four qualitative traits ranged from 0.35 to 0.98, which was significantly lower than the quantitative traits. Among them, the variation coefficient of segment membrane and juice sac wall weight is the largest, and peel color have the largest genetic diversity index. Principal component analysis was performed on 17 fruit phenotypes, and the top five principal components have the cumulative contribution rate more than 70%. Factor analysis was used to conduct a comprehensive evaluation, it was used to select elite mandarin accessions with the comprehensive evaluation score which ranged from -1.23 to 1.59, the cultivar with the highest score was LP31 (Nishinokaori×Jin Kui), followed by LP45 (Nishinokaori×Jin Kui), LP18 (Benimadona×American Tang Ju), LP3 (Tarocco Blood Orange×Jin Kui). Both the phenotypic cluster analysis results and the phylogenetic tree analysis divided the tested mandarin germplasm resources into 7 groups, different groups can reflect the differences in the origin, variety type and hybrid combination derived from different genetic backgrounds. The germplasms with high comprehensive evaluation scores mostly are concentrated in Group Ⅳ, which showed that these excellent germplasms have similar genetic component. 【Conclusion】 The 473 mandarin accessions used in this study has extensive phenotypic variation and rich genetic diversity. The phenotypic cluster analysis results and phylogenetic tree gave similar classification results, and the excellent germplasm selected based on comprehensive evaluation score have high genetic similarity.

Key words: mandarin, phenotypic identification, genetic diversity, whole-genome resequencing, phylogenetic evolution