甜玉米小斑病抗性的遗传分析与主效QTL定位

为培育抗病品种,利用抗小斑病甜玉米自交系T14和感小斑病自交系T18为亲本配制杂交组合,对玉米抗小斑病性状进行遗传分析和抗病基因分子标记定位,用主基因＋多基因混合遗传模型和P₁、P₂、F₁、B₁、B₂、F₂ 6世代联合分析的方法对单位叶面积病斑数量进行遗传分析,并应用复合区间作图法检测抗小斑病QTL。结果表明,单位叶面积病斑数量受2对加性-显性-上位性主基因控制,自交系T14的抗病性在各个分离世代都以主基因遗传为主。在第4染色体上检测到4个相互连锁的小斑病抗性QTL,解释表型变异的7.7%、30.9%、14.8%和11.5%;在第6染色体上定位了1个抗病QTL,可解释表型变异的37.7%。检测到的小斑病抗性主效QTL位于第4和第6染色体的特征与2对主基因的遗传模型相吻合。

Genetic analysis and main QTL mapping for resistance to Bipolaria maydis in sweet corn

For breeding broad-spectrum resistant cultivars to southern corn leaf blight (SCLB), a resistant corn inbred (T14) was crossed with a susceptible inbred (T18) to identify markers for Bipolaria maydis resistance genes and validate the mode of its inheritance. Genetic segregation analysis for B.maydis resistance was evaluated based upon lesion number per leaf area in the seedling stage using major gene-polygene mixed inheritance models and joint analysis of P₁, P₂, F₁, B₁, B₂ and F₂ populations obtained from the cross T14×T18. The result showed that resistance of sweet corn inbred T14 to B.maydis was controlled by two major genes with additive-dominance-epistatic effects, and the inheritance of the major gene was dominant. Furthermore, we carried out QTL screening with the method of multiple interval mapping (CIM). Four linked resistance QTLs to B.maydis were found on chromosome 4, counting for 7.7%, 30.9%, 14.8% and 11.5% of phenotypic variance. One resistance QTL was screened on chromosome 6, controlling 37.7% of variation. The genetic model of two major genes in T14 is consistent with QTL screening result that all resistance main QTL found in this research were distributed on only two chromosome.