玉米抗穗粒腐病QTL定位研究

QTL Mapping for Resistance to Fusarium Ear Rot in Maize

【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Mapmaker3.0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1396.3cM的连锁图谱,标记间的平均遗传图距9.43cM。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。

【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.