Sichuan Key Laboratory of Ecological Restoration and Conservation for Forest and Wetland, Sichuan Academy of Forestry, Chengdu, China.
Forestry Ecological Engineering in the Upper Reaches of the Yangtze River Key Laboratory of Sichuan Province, National Forestry and Grassland Administration Key Laboratory of Forest Resource Conservation and Ecological Safety on the Upper Reaches of the Yangtze River, College of Forestry, Sichuan Agricultural University, Chengdu, China.
BMC Plant Biol. 2024 Nov 18;24(1):1091. doi: 10.1186/s12870-024-05810-1.
Phoebe zhennan, commonly known as "golden-thread nanmu," is one of the most valuable and protected tree species in China. An accurate understanding of the population genetic structure and its environmental factors is of significance for the protection and selection of new P. zhennan varieties.
Sixteen nSSR and six cpSSR markers were used to determine the genetic diversity and population structure of P. zhennan and the effect of environmental factors on the genetic structure. The nSSR markers identified a total of 451 number of alleles (Na), while cpSSR markers detected 20 Na. A relative high level of genetic diversity was observed in the P. zhennan population evidenced by high Shannon's information index (I) of 0.671 and 2.294 based on cpSSR and nSSR datasets. The low value of fixation index (F) observed from the nSSR dataset indicated low breeding within the population. The genetic differentiation was mainly detected within populations (only 28% and 13% of the variance being between populations according to the nSSR and cpSSR datasets). Among them, the HNSZX (H = 0.469) and SCSZZ (I = 1.943) populations exhibited the highest level of genetic diversity, while the HNXXT (H = 0.041) and SCLJS (I = 0.943) populations exhibited the lowest level of genetic diversity. The average genetic differentiation coefficient (Fst) and gene flow (Nm) were 0.022-0.128 and 1.698-11.373, respectively, which indicated a moderate level of genetic differentiation and a high level of gene flow. STRUCTURE, neighbor-joining clustering, and principal coordinate analysis divided 543 individuals into two or three categories based on the nSSR or cpSSR datasets. Four temperature, three precipitation, five chemical, five physical, and one soil texture variable showed significant effects on the genetic structure and distribution of P. zhennan populations. Compared to nSSR, the genetic differentiation among populations based on cpSSR datasets conformed to the geographic isolation model, suggesting that geographic and genetic distances should be considered for further genetic conservation and breeding utilization. The importance of in situ conservation units, such as populations with a high level of genetic diversity, more private alleles, and haplotypes (e.g., population SCGTS, SCYFS, and YNYJX), should be emphasized. Additionally, breeding, along with artificially assisted population regeneration and restoration, should also be carefully planned, taking into account climate and soil properties at the same time.
In conclusion, this study provided genetic background information for the genetic conservation, management, and utilization of P. zhennan.
桢楠俗称“金丝楠木”，是中国最有价值和受保护的树种之一。准确了解种群遗传结构及其环境因素对于保护和选择新的桢楠品种具有重要意义。
利用 16 个核 SSR 和 6 个叶绿体 SSR 标记，研究了桢楠的遗传多样性和种群结构，以及环境因素对遗传结构的影响。核 SSR 标记共鉴定出 451 个等位基因（Na），而叶绿体 SSR 标记检测到 20 个 Na。基于叶绿体 SSR 和核 SSR 数据集，桢楠种群表现出较高的遗传多样性，Shannon 信息指数（I）分别为 0.671 和 2.294。核 SSR 数据集的固定指数（F）值较低，表明种群内的繁殖能力较低。遗传分化主要发生在种群内（根据核 SSR 和叶绿体 SSR 数据集，只有 28%和 13%的方差存在于种群间）。其中，HNSZX（H=0.469）和 SCSZZ（I=1.943）种群遗传多样性最高，HNXXT（H=0.041）和 SCLJS（I=0.943）种群遗传多样性最低。平均遗传分化系数（Fst）和基因流（Nm）分别为 0.022-0.128 和 1.698-11.373，表明遗传分化程度中等，基因流水平较高。STRUCTURE、邻接聚类和主坐标分析根据核 SSR 或叶绿体 SSR 数据集将 543 个个体分为两类或三类。四个温度、三个降水、五个化学、五个物理和一个土壤质地变量对桢楠种群的遗传结构和分布有显著影响。与核 SSR 相比，基于叶绿体 SSR 数据集的种群间遗传分化符合地理隔离模型，表明在进一步的遗传保护和育种利用中应考虑地理和遗传距离。应强调具有高水平遗传多样性、更多特有等位基因和单倍型的种群（如种群 SCGTS、SCYFS 和 YNYJX）等原地保护单元的重要性。此外，还应仔细规划繁殖以及人工辅助种群再生和恢复，同时考虑气候和土壤特性。
综上所述，本研究为桢楠的遗传保护、管理和利用提供了遗传背景信息。
