玉米显性矮秆基因D11的精细定位及其育种潜势的研究

Dwarf stature is introduced to improve lodging resistance and harvest index in crop production. In many crops including maize, mining and application of "new" dwarf genes is urgent to overcome genetic bottleneck and vulnerability during crop improvement and breeding. To this end, we aimed at fine-mapping and unraveling breeding value of a newly identified maize dominant gene D11 (Dwarf11) in this project. The goals of this project are to: 1) evaluate breeding value of D11 gene based on agronomic traits investigation and combining ability estimation under different years and environmental conditions; 2) unravel cytological characteristics of organs and tissues of D11 plant in different developmental stages using scanning electron microscopy and paraffin sections techniques; 3) explore the possible relationship of dwarfism and phytohormone gibberellin (GA) by measuring endogenous GA content, exogenous GA application response, and activity of α-amylase triggered by GA induction. Finally, high saturated markers combined with large advanced backcross population were adopted to finely map of D11 gene. Results from this project will lay a foundation for the following D11 gene cloning and functional characterization. Additionally, results from this project will aid in crop genetic improvement and breeding, especially breeding for an ideal plant type.

矮秆基因被用来增强作物的抗倒性与提高收获指数，玉米矮秆基因的育种应用与基础研究工作亟待拓宽矮秆基因的种质来源，丰富矮秆基因的遗传基础。本申请项目在前期研究基础上，对一份新的玉米显性矮秆材料D11进行基因精细定位与育种潜势的研究：基于多年多点性状考察与配合力效应值估算，评价矮秆性状的育种潜势；不同发育时期、取样不同组织，扫描电镜、石蜡切片观察，解析矮秆系关键发育节点的细胞学特征；通过度量内源赤霉素含量、外源赤霉素施用响应、赤霉素诱导的籽粒α-淀粉酶活性等生理指标，探析D11显性矮秆性状与赤霉素通路的关联性；高世代回交大群体结合高密度分子标记，精细定位矮秆基因。本申请项目研究旨在为矮秆基因D11的克隆和功能分析工作奠定基础，也为作物株型改良等育种工作提供理论参考、技术支撑与实践素材。

矮秆基因被用来增强作物的抗倒性与提高收获指数，玉米矮秆基因的育种应用与基础研究工作亟待拓宽矮秆基因的种质来源，丰富矮秆基因的遗传基础。本项目对一份玉米显性矮秆材料D11进行了育种潜势评价、细胞学特征解析、基因精细定位、矮秆性状与赤霉素通路关联性的研究。主要结果如下：1）对矮秆材料D11与不同杂种优势群自交系杂交后代的表型进行鉴定，结果表明D11与郑58杂交后代突变体的株高未发生变化、果穗退化，D11与昌7-2 杂交后代突变体的株高变高、果穗发育正常。在D11与昌7-2杂交后代中已筛选出株型较好的材料，应用于玉米育种工作。2）徒手切片、扫描电镜技术解析矮秆材料D11的细胞学特征，结果表明D11茎秆细胞大小不一、排列散乱、相互挤压，呈无序状，茎秆维管束较少且分布散乱，茎秆高度木质化。D11的矮化表型是由于节间细胞纵向伸长受到抑制所导致。3）采用集团分离分析的方法，矮秆基因D11被初定位于玉米第2染色体的标记umc1516与phi101049之间。采用初定位使用的多态性标记、目标区域新发展的多态性标记筛选大的回交群体，鉴定交换株，进行D11的精细定位。D11被定位于分子标记M19与M20之间，物理距离约143 kb。4）矮秆材料D11的矮化表型与赤霉素通路关联性的研究结果表明，在赤霉素GA3诱导下，D11的籽粒能够产生α-淀粉酶，表明D11赤霉素的信号通路正常；D11的内源赤霉素GA3含量显著降低；外源赤霉素GA3处理，D11的株高、第二叶鞘长度显著增加，表明D11对外源赤霉素GA3的施用敏感。D11的矮化表型是由于赤霉素生物合成的缺陷所导致，而不是由于赤霉素信号转导通路的异常所造成。综合本项目表型观察、外源赤霉素施用响应、内源赤霉素含量测定、基因定位等结果，表明D11不同于已报道的3份玉米显性矮秆材料D8、D8-1023、D9，为一新的玉米显性矮秆材料。本项目研究所得结果为矮秆基因D11的克隆和功能分析工作奠定了基础，也能为作物株型改良等育种工作提供技术支撑与实践素材。