中国西北地区天然胡杨群体遗传多样性及核心保护单元的构建

胡杨(Populus euphratica)是极端干旱荒漠区的珍稀乔木树种。为了确定天然胡杨群体遗传多样性保护单元并挖掘优异的种质资源, 本研究以中国西北地区新疆、青海、甘肃、宁夏、内蒙古的58个天然胡杨群体为研究对象, 利用120个位点的SNPs标记对这些胡杨群体进行群体遗传结构和遗传多样性分析, 并根据不同群体间Nei’s遗传相似度, 采用逐步聚类优先取样法对初始群体、遗传多样性保护单元和剩余群体进行t检验。群体结构和主成分分析表明, 胡杨群体可分为新疆南疆(SX)、新疆北疆(NX)、青海(QH)和混合群(甘肃、宁夏和内蒙古混合群, GNM) 4个分支, 遗传多样性分析表明新疆南疆(SX)遗传多样性高于其他群体。分子方差分析(AMOVA)表明天然胡杨群体的遗传变异主要分布在各个群体内。构建了天然胡杨群体一级核心保护单元3个群体(CU3), 二级核心保护单元33个群体(CU33)。南疆存在较多优异抗逆的天然胡杨古树资源, 南疆分布区的平均遗传多样性水平最高。综上所述, 南疆地区胡杨古树遗传多样性整体高于北疆及疆外地区, 结合新疆地区干旱严重指数等生境信息, 建议加大对南疆胡杨古树群体的保护力度, 重视北疆胡杨林的更新换代。

Genetic diversity and construction of core conservation units of the natural populations of Populus euphratica in Northwest China

Aims: Populus euphratica is a rare tree species in the extremely arid desert area of northwest China. The research on the germplasm genetic resources within the natural populations and the construction of a germplasm bank are helpful to protect the gene resources of P. euphratica.
Methods: In this study, according to the Nei’s genetic similarity among populations by using SNPs from 120 DNA fragments, the gradual clustering priority sampling method was used and t-test was performed to compare the genetic diversity within populations, the conservation units and the rest populations. A total of 58 natural P. euphratica populations from northwest China, including Xinjiang, Qinghai, Gansu, Ningxia, and Inner Mongolia, were used to obtain the different natural conservation units.
Results: The P. euphratica populations were divided into four distinct clades that demonstrated strong geographical distribution patterns (NX, SX, QH and GNM, with the GNM clade containing individuals from Gansu, Ningxia and Inner Mongolia individuals). PCA analysis confirmed the differentiation of populations, similar to population structure. Southern Xinjiang holds the major distribution of P. euphratica in China, and the higher genetic diversity than other distribution areas, and the analysis of molecular variance (AMOVA) showed that most of the variation within P. euphratica was distributed within population compared to the variation among populations. The primary core conservation units (CU3) contained three populations, and the secondary core conservation units (CU33) contained 33 populations. There may be natural ancient P. euphratica resources with putative resistance to stress in southern Xinjiang, and the average genetic diversity in southern Xinjiang was higher than that in northern Xinjiang.
Conclusion: The overall genetic diversity of P. euphratica and the number of ancient trees in southern Xinjiang were higher than those in northern Xinjiang. The priority protection of the first and second core conservation units was constructed. Combining comprehensively with habitat information, such as the severity of drought index in Xinjiang, it was recommended to increase the conservation of ancient P. euphratica trees in southern Xinjiang, and to pay more attentions to the regeneration of P. euphratica forests in northern Xinjiang.