摘要：
[Objective]The aim of this study was to identify simple sequence repeat (SSR) loci associated with fall dormancy in alfalfa (Medicago sativa L.) for understanding its inheritance pattern and molecular mechanism.[Method]The association population was composed of a total of 321 tetraploid genotypes from 75 alfalfa accessions,and each of the Chinese accessions was represented by six to eight genotypes,while the remaining ones included three to four genotypes.All the 321 materials were genotyped using 85 SSR markers randomly distributed on alfalfa genome.The phenotyping data of fall dormancy trait of these alfalfa accessions was obtained in 2014 and 2015,and used together with the SSR genotyping results for an association mapping by using General Line Model (GLM) and Mixed Line Model (MLM) models.[Result] It was showed that the fall dormancy trait in alfalfa was significantly influenced by genotypes,years,and genotype × year interactions.The fall plant heights ranged between 5.1 cm and 55.1 cm,and between 3.5 cm and 44.9 cm,averages of 22.4 cm and 15.2 cm,and coefficients of variation at 45.5％ and 43.7％ in 2014 and 2015,respectively.This trait showed a normal or nearly normal distribution in both 2014 and 2015 and had a relatively high broad-sense heritability at 0.71.The MLM model which adequately controlled false positives identified a total of 12 and 11 significant associations accounting for 2.42％ to 6.73％ and 2.45％ to 4.81％ of the phenotypic variances in 2014 and 2015,respectively.Among them,four loci of m83_157 on Chr.2,m525_230 and m525_231 on Chr.3,and m429_245 on Chr.4 were detected in the two years by using the two models.[Conclusion] It was concluded that the four association loci related to fall dormancy in alfalfa were identified,and would be subjected to functional verification so that they could be eventually used for alfalfa marker assisted selection breeding.%[目的]发掘紫花苜蓿秋眠性关联位点,为揭示紫花苜蓿秋眠性状的遗传规律和分子机制提供理论依据.[方法]紫花苜蓿关联群体由7 5份321个四倍体紫花苜蓿基因型构成,其中中国紫花苜蓿品种每份材料选取6-8个基因型;其余材料每份选取3-4个基因型.利用紫花苜蓿基因组均匀分布的85对SSR (Simplesequence repeats)标记,对321个紫花苜蓿基因型进行扫描.于2014-2015年连续两年对紫花苜蓿秋眠性开展调查,并利用一般线性模型(GLM)及混合线性模型(MLM)2种方法,开展秋眠性与SSR分子标记的关联分析.[结果]紫花苜蓿秋眠性表现出极显著的基因型、年际及基因型×年际互作效应.2014年,表型变异幅度为5.1-55.1 cm,平均值为22.4 cm,变异系数为45.5％.201 5年,变异幅度在3.5-44.9 cm,平均为15.2 cm,变异系数为43.7％.秋季株高两年均呈现接近正态分布特征.广义遗传力为0.71. MLM模型很好的控制了紫花苜蓿秋眠性的假阳性关联.基于MLM模型,在2014年共找到1 2个显著关联的SSR位点,表型贡献率为2.42％6.73％.2015年共找到11个,表型贡献率为2.45％-4.81％.在这些关联位点中,分布于Chr 2的m83_157、Chr 3的m525_230和m525_231、及Chr 4的m429_245,在两种模型及两年内均被重复检测到.[结论]通过两种模型发掘到4个与紫花苜蓿秋眠性显著相关的位点,经过验证后可以用于紫花苜蓿秋眠性分子标记辅助选择育种.
