玉米尾孢灰斑病抗性主效QTL精细定位与候选基因发掘

Gray leaf spot is a new maize disease infected by Cercospora zeina. Character of genetic resistance of this disease has not been reported so far. Preliminary QTL analysis was preformed through phenotype identification of F2:3 family generated by inbred line R225 (highly resistant to gray leaf spot) and inbred line YE478 (highly susceptible to gray leaf spot) selected by our research group at three locations during two years. Previous study showed that the resistance to gray leaf spot in southwest China is a quantitative trait controlled by polygenes. We have identified several resistance-related QTLs on different chromosomes. Among those QTLs identified, the “qRcz2” is a stable and major QTL on chromosome 2 and it has been verified by marker-assisted selection combined the field experiment. On the basis of previous work, further study of fine mapping for qRcz2 locus will be conducted by advanced backcross lines of BC1F7, develop molecular markers closely linked to resistance-related major QTL, obtain genomic sequence of the region of target genes, and determine the candidate genes by gene annotation. This study will provide supportive information for cloning and isolation of resistance genes and provide new approach and theoretical foundation for molecular breeding for disease resistance of gray leaf spot.

由尾孢菌(Cercospora zeina)侵染引起的玉米灰斑病是近几年发生的一种新病害。对于该病的抗性遗传研究前人尚无公开报道。课题组利用多年鉴定筛选的高抗灰斑病自交系R225与高感自交系掖478所组配的F2:3家系通过2年3点表型鉴定，进行QTL初定位，阐明了西南地区玉米灰斑病抗性是一个多基因控制的数量性状，并在不同染色体上定位了多个抗性QTL，尤其以第2染色体上的QTL“qRcz2”效应明显，表达稳定且已被标记辅助选择试验验证，是一个可靠的主效QTL。本研究将在已有工作的基础上，拟采用高世代回交分离群体BC1F7继续深入对qRcz2位点进行精细定位，发掘与抗病主效QTL紧密连锁的分子标记，获得目标基因区间的基因组序列，对其进行基因注释筛选获得候选基因。为进一步抗病基因的分离与克隆奠定基础，同时为抗灰斑病分子育种提供新的途径和理论依据。

由尾孢菌(Cercospora zeina)侵染引起的玉米灰斑病是近几年发生的一种新病害。种植抗病品种是防治该病害最有效的途径。课题组利用多年鉴定筛选的高抗灰斑病自交系R225与高感自交系掖478所组配的F2:3家系通过2年3点表型鉴定，进行QTL初定位，阐明了西南地区玉米灰斑病抗性是一个多基因控制的数量性状，并在不同染色体上定位了多个抗性QTL，尤其以第2染色体上的QTL“qRcz2”效应明显，表达稳定且已被标记辅助选择试验验证，是一个可靠的主效QTL。本研究将在已有工作的基础上，采用高世代回交分离群体继续深入对qRcz2位点进行精细定位，用回交后代验证的方法将目标QTL定位于umc1422~umc1265标记之间。同时以简化基因组测序技术SLAF-seq测序，在2号染色体检测到了主效QTL，与连锁群体进行定位的结果一致。获得189,966个SLAF 标签，559,927个单核苷酸多态(SNP)，最终获得49,488个进行后续关联分析，对其进行基因注释筛选获得候选基因。利用 SNP － index 方法定位关联区域，分析关联区域内的基因在两个亲本之间 SNP，对这些 SNP 进行变异的注释，发现 12个非同义突变的 SNP，对应到6个基因上。进行多个数据库（NR、Swiss-Prot、GO、KEGG、COG）的深度注释，注释为蛋白质激酶或者蛋白丝氨酸/苏氨酸激酶，这些基因有可能是与性状直接相关的功能基因，还需进一步对这6个候选基因进行功能验证分析。本研究为进一步抗病基因的分离与克隆奠定基础，同时为抗灰斑病分子育种提供新的途径和理论依据