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【目的】分析细叶桉天然群体的多样性水平和遗传结构,为种质资源管理和育种利用提供有用信息;检测细叶桉与原产地气候因子显著关联的基因组位点,探索气候适应过程中趋异选择的分子证据。【方法】以细叶桉9个群体的77株样品为材料,基于覆盖巨桉全基因组的108个SSR位点(包括44个基因组SSRs和64个ESTSSRs),利用不偏离哈-温平衡、F_(ST)值非异常的25个中性的基因组SSRs进行群体多样性水平和遗传结构分析,利用所有位点进行F_(ST)异常值检测、再利用空间分析法查找与原产地气候因子关联的适应性位点,注释适应性位点的功能,并通过等位片段在各群体的频率与气候因子的一元线性回归进一步验证关联的显著性。【结果】25个中性的基因组SSR位点对细叶桉9个群体扩增,共检测到556个等位片段、平均每个位点22.2个等位片段,位点多态性较高;群体多样性水平都较高,期望杂合度为0.711~0.847(平均0.800)、基因丰富度为3.054~3.386(平均3.246),各群体特有等位片段数为6~26(平均14.4);群体间分化水平较低,25个中性位点平均F_(ST)仅0.012,分子方差分析中群体间方差分量仅占1.2%,表明细叶桉遗传变异主要存在于群体内;聚类分析也表明群体分化水平较低。所有108个位点中,共检测到78个F_(ST)值异常的位点,与年均气温、年均降水、最热月最高温度和季节性降水变异系数相关的F_(ST)值异常的位点数分别为27,10,51和42个,即为受选择位点;其中,4个F_(ST)值异常的位点各有1个等位片段在空间分析法中与1个或者2个气候因子显著关联,EUCe SSR485与季节性降水变异系数相关、为富含羟脯氨酸的蛋白家族基因,EUCe SSR0497与年均气温和年均降水均相关、与跨膜内切1,4-β-葡聚糖酶基因同源,而另外2个没有明确的功能注释;线性回归分析验证了1个等位片段(EUCe SSR485-140 bp)与季节性降水变异系数的回归显著性(P≤0.05)。【结论】细叶桉群体的遗传多样性高,育种利用的潜力大,种质资源管理应重视多样性较高和特有等位片段较多的群体;细叶桉群体的遗传分化较低,其适于关联遗传分析;受选择位点的鉴定有助于理解林木适应环境的分子机制和探索林木环境适应性的潜力。
【Objective】 The objective of this study was to analyze the diversity and genetic structure of Eucalyptus globulus natural populations and to provide useful information for germplasm resources management and breeding use. To detect the genomic loci that Eucalyptus globulus and climate elements of origin are significantly associated with, Molecular evidence of divergent selection. 【Method】 A total of 108 SSR loci (including 44 genomic SSRs and 64 ESTSSRs) covering the whole genome of E. grandis were collected from 77 samples from 9 populations of E. grandis. (ST) value of non-abnormal 25 neutral genomic SSRs for population diversity and genetic structure analysis, the use of all sites F_ (ST) outlier detection, and then use spatial analysis to find the origin of climate factors associated Adaptive sites, annotating the function of adaptive sites and further verifying the significance of the association by means of a univariate linear regression of the frequency of the allelic fragments in each population with climatic factors. 【Result】 The 25 neutral genomic SSR loci were amplified from 9 populations of Eucalyptus urophylla. A total of 556 alleles were detected, with an average of 22.2 alleles per locus, with a high locus polymorphism. The population heterogeneity was high, with expected heterozygosity ranging from 0.711 to 0.847 (average 0.800), gene abundance ranging from 3.054 to 3.386 (average 3.246), and the number of specific alleles in each population ranging from 6 to 26 (average 14.4) The average level of F_ (ST) was only 0.012 in 25 neutral loci and only 1.2% of the variance of variance in molecular variance analysis, indicating that the genetic variation of Eucalyptus urophylla mainly existed in the population. Cluster analysis also showed that the population The level of differentiation is low. In all 108 loci, 78 loci with abnormal F_ (ST) values were detected. The F_ (ST) values related to the annual mean temperature, the average annual precipitation, the warmest month maximum temperature and the coefficient of variation of seasonal precipitation were abnormal The number of loci was 27, 10, 51 and 42, respectively, which were selected sites. Among them, one locus of four abnormalities in F_ (ST) 2 climate factors, EUCe SSR485 is related to the coefficient of variation of seasonal precipitation and is a hydroxyproline-rich protein family gene. EUCe SSR0497 is correlated with annual mean temperature and annual precipitation, β-glucanase gene homology, while the other two did not have a clear functional annotation; linear regression analysis confirmed the regression significance of one allelic fragment (EUCe SSR485-140 bp) and seasonal precipitation variation coefficient (P ≤0.05). 【Conclusion】 Eucalyptus urophylla populations have high genetic diversity and potential for breeding and utilization. Germplasm resources management should pay more attention to groups with higher diversity and more unique allelic fragments. Eucalyptus globules have lower genetic differentiation, Appropriate for genetic analysis; Identification of selected sites can help to understand the molecular mechanism of forest adaptation to the environment and to explore the potential of forest adaptation.