裸燕麦SSR标记连锁群图谱的构建及β-葡聚糖含量QTL的定位

Construction of SSR Genetic Linkage Map and Analysis of QTLs Related to β-glucan Content of Naked Oat(Avena nuda L.)

【目的】构建裸燕麦分子遗传图谱,发掘燕麦β-葡聚糖基因紧密连锁的分子标记,为高β-葡聚糖含量燕麦种质资源的利用及裸燕麦分子标记辅助育种提供理论和实践依据。【方法】以高β-葡聚糖地方品种夏莜麦为父本,育成品种赤38莜麦为母本构建的包含215个F2:3家系为图谱构建群体,利用SSR分子标记进行遗传分析,构建分子遗传图谱。通过美国谷类化学会(AACC)发表的标准葡聚糖含量测定方法(AACC Method 32-23)测定各家系的β-葡聚糖含量,利用复合区间作图法进行燕麦β-葡聚糖含量性状进行遗传定位与分析。【结果】利用筛选出的231对SSR引物在F2后代群体上进行检测,共得到261个多态性标记位点,利用JoinMap 4.0软件对上述获得多态性分子标记进行遗传连锁分析,在LOD≥5.0情况下,构建遗传图谱,得到包含26个连锁群、182个标记位点的遗传图谱,覆盖基因组1 869.7 cM,标记间平均距离为10.6 cM,每个连锁群上的标记数在2—14个之间,连锁群长度在10.6—235.1 cM。对亲本及后代群体β-葡聚糖含量的测定结果表明,β-葡聚糖含量在后代群体中表现出明显的分离,且呈现为连续变异,变异系数为18.72%,说明β-葡聚糖含量性状是受多基因控制的数量性状,群体符合QTL定位的要求。利用QTL分析软件WinQTLCart 2.5对SSR数据进行分析,采用复合区间作图法(composite interval mapping,CIM)对全基因组进行QTL扫描,以LOD值5作为阈值对β-葡聚糖含量可能存在的QTL进行定位和效应估计,检测到4个与β-葡聚糖含量相关的QTL位点,其中qBG-1位于连锁群LG20上,与最近的标记AM591的距离10.0 cM。加性效应值为0.21,可以解释的表型变异为10.9%;qBG-2和qBG-3位于连锁群LG23上,其中qBG-2与最近的标记AM1823的距离4.6 cM,qBG-3与最近的标记AM641的距离1.9 cM,加性效应值分别为-0.23和-0.22,可以解释的表型变异分别为3.2%和2.7%;qBG-4位于连锁群LG25上,与最近的标记AM302的距离6.8 cM,加性效应为0.84,可以解释的表型变异为27.6%,其中存在的2个主效QTL qBG-1和qBG-4,都来自于高β-葡聚糖含量的父本夏莜麦。【结论】构建了大粒裸燕麦SSR分子标记连锁群图谱,并定位了4个控制β-葡聚糖含量的QTL位点。

[Objective] A molecular genetic linkage map for cultivated naked oat based on SSR markers was developed and Quantitative Trait Loci influencing β-glucan content were identified, in order to facilitate the utilization of high β-glucan content oat germplasm resources and provide a theoretical basis for oat molecular marker-assisted selection. [Method] Taken a segregation population of 215 F2：3 lines which originated from the cross with the high β-glucan content local cultivar Xiayoumai was used as the male parent and improved cultivar Chi38 Youmai as the female as mapping population, a molecular genetic linkage map of oats withSSR markers was developed. The β-glucan content of segregation population was determined by the standard β-glucan measure method （AACC Method 32-23） which was published by American Association of Cereal Chemists and the QTLs for β-glucan content of oat were analyzed and identified by Composite Interval Mapping method. [Result] After detection ofF2 progenies with 231 pairs of SSR primers, a total of 261 polymorphic markers were obtained. The polymorphic markers mentioned above were analyzed for their genetic linkage relationship by JoinMap 4.0 and finally the oat genetic linkage map was constructed. The map included 26 linkage group, 182 SSR markers and covers 1869.7cM of the whole genome. The average space between markers was 10.6 cM. The number of markers in each linkage group varied from 2 to 14 and the length of the linkage group varied from 10.6 to 235.1 cM. The results of the measurement of the parents and segregation population＇s β-glucan content showed that β-glucan content in the offspring groups presented as significant separation and continuous variation with variation coefficient of 18.72%, which indicated that J3-glucan content traits are controlled by multiple genes of quantitative traits and the segregation population meets the requirements of QTL mapping. The SSR data were analyzed by QTL analysis software WinQTL Cart 2.5 and whole genome were scanned by Composite Interval Mapping method to identify the possible QTLs for β-glucan content and estimate QTL effect with the LOD=5 as a threshold. Four QTLs correlative to β-glucan content were found, qBG-1 was on the twentieth linkage group and explained 10.9% of phenotype variation with the additive genetic effects value is 0.21 and the nearest marker AM591 showed a genetic distance of 10.0 cM to qBG-1, qBG-2 and qBG-3 were on the twenty-third linkage group and explained 3.2% and 2.7% of phenotype variations with the additive genetic effects values of-0.23 and -0.22, respectively, and the nearest marker AM1832 showed a genetic distance of 4.6cM to qBG-2 and 1.9 cM to qBG-3 by AM641, qBG-4 was on the twenty-fifth linkage group and explained 27.6% of phenotype variation with the additive genetic effects value of 0.84 and the nearest marker AM302 showed a genetic distance of 6.8 cM to qBG-4. The two main QTLs, qBG-1 and qBG-4, all originated from the high fl-glucan content male parent Xiayoumai. [ Conclusion ] A genetic linkage map was constructed, and four QTLs which affect β-glucan content of naked Oat were identified, thus providing a scientific basis for molecular marker-assisted selection in oat breeding.