玉米抗穗粒腐病 QTL 定位研究

    QTL Mapping for Resistance to Fusarium Ear Rot in Maize

    • 摘要: 【目的】在连作程度高且更利于发病的广西等一年两熟玉米种植地区开展玉米穗粒腐病抗性数量性状位点(QTL)定位研究,揭示玉米穗粒腐病抗性遗传变异的基本规律,为这些地区玉米穗粒腐病抗性育种提供一定的理论依据。【方法】用 Mapmaker 3.0 软件对 148 个多态性 SSR 标记在 215 个 F2 单株间的基因型数据构建遗传图谱。在广西南宁用针刺法对由 215 个 F2 单株发展而来的 F2:3 家系抗病性进行田间接种鉴定,记录家系内各单株的病级,将家系内各单株的病级换算成家系的抗病指数。利用 winQTLCart2.5 软件中的复合区间作图法对各家系的抗病指数进行抗病 QTL 分析。【结果】148 个 SSR 标记构建了覆盖玉米 10 条染色体组总长度 1 396.3 cM 的连锁图谱,标记间的平均遗传图距 9.43 cM。抗病指数在 α= 0.05 显著水平下进行 500 次排列检验计算得到 LOD 阈值为 2.2。以 2.2 这个阈值为依据共检测到 3 个抗病指数 QTL 位点。这 3 个 QTL 的基因作用方式分别为超显性、超显性和部分显性。各 QTL 的加性效应值有正有负,说明抗感亲本中均含有微效抗病基因。【结论】检测到的 3 个穗粒腐病抗病 QTL 分别位于第 2、3、10 染色体上,可解释表型变异的 4.6%~6.6%,它们均为微效 QTL。未检测到较大效应值的主效 QTL。

       

      Abstract: 【Objective】In order to discover some basic regulations of maize’s resistance to Fusarium ear rot in Guangxi, where maize was planted by the cropping system of two crops a year and had beneficial occurrence conditions to Fusarium ear rot, the objectives of this study were to detect QTLs (quantitative trait loci) associated with resistance to F. verticillioides and to provide some theoretical basis for the resistance breeding of maize ear rot in these areas.【Method】 Based on the genotypic date of 148 polymorphic SSR markers among 215 F2 plants, a linkage map was constructed by using software Mapmaker 3.0. F2:3 lines, which developed from 215 F2 plants, were artificially inoculated to identify their resistance to Fusarium ear rot by using the needle-punch method in Nanning.The infected grade of every plant in a line was recorded after field investigation, then all the infected grades in a line were transformed into resistance index of corresponding line. The resistance QTLs were analyzed by composite interval mapping (CIM) method of software WinQTLCart 2.5.【Result】 A linkage map was constructed 148 SSR markers, covering 10 maize chromosomes with a total length of 1 396.3 cM and the average genetic distance of 9.43 cM. The obtained LOD threshold value was 2.2 after the permutation test calculation was conducted for 500 times with the disease resistance index at a significant level of 0.05. Based on this threshold value, 3 disease resistance QTLs were detected. The result of gene action showed that these 3 QTLs were over-dominant, over-dominant and partial dominant, respectively. These QTLs had both positive and negative effects on additive value, which reflected that there were minor resistance genes in both resistant and susceptible parents.【Conclusion】The 3 QTLs were located on chromosome 2, 3 and 10, explaining 4.6%-6.6% of the phenotypic variation and they were minor resistance QTLs. No major resistance QTL with large effect value was found in this study.