一个新的玉米南方锈病主效抗病基因的精细定位和分离

Southern corn rust (SCR) is one of the most devastating foliar diseases in maize. Isolation of the resistance gene will play an important role in understanding the resistance molecular mechanism and utilization in maize breeding programs. In previous reports, a resistance gene cluster was identified on the short arm of chromosome10, However, no genes resistant to SCR have been cloned. In our previous study, one major gene, RppCML496, was identified in the resistant inbred line ‘CML496’ to confer resistance against SCR. In this study, based on the materials including linkage mapping population, mutant and association mapping population, isolating the RppCML496 will be carried out by map-based cloning strategy. The current project includes two parts: 1) For fine-mapping RppCML496, near isogenic lines (NILs) segregating at RppCML496 loci will be genotyped by molecular markers for screening recombinant lines. Combined with the resistance evaluation, the RppCML496 region can be expected to delimit to 50Kb, in which the candidate genes can be predicted based on B73 reference genome. 2) For verifying the target gene, the candidate genes will be re-sequenced in resistant line CML496, susceptible line Lx9801 and mutant line CML496S, by which the target gene can be screened based on the difference of sequence in candidate genes. Then, the expressional characteristic of target gene will be analyzed at RNA level in various maize tissues. Based on the re-sequencing analysis of target gene and the resistance evaluation of association mapping population, the functional variation of target gene can be identified by candidate gene association mapping. The information from cloning and functional analysis of RppCML496 can help to reveal the molecular resistance mechanism and molecular assisted breeding in maize resistance breeding programs.

玉米南方锈病是玉米生产上普遍发生的真菌性病害。已有研究表明，在玉米第10染色体短臂上存在一个抗病基因富集区。然而，由于该区域基因组结构的复杂性，迄今还没有克隆出抗病基因的报道。课题组在对该区域抗病基因RppCML496初步定位的基础上，拟以材料创新为切入点，利用已创建的连锁群体、突变体和关联群体等材料，采用图位克隆技术分离抗病基因。研究包括两个阶段：1.抗病基因精细定位：在初步定位的274Kb抗病区域内开发分子标记，采用近等基因系作图群体进行RppCML496的精细定位，把抗病基因限定在50Kb的范围内；2.抗病基因的分离：利用生物信息学方法对该区域进行基因预测，并结合预测基因在抗、感亲本和突变体间的序列差异筛选候选基因；通过候选基因关联分析和表达分析进行功能验证，最终实现RppCML496的分离。本项目的实施将为解析玉米南方锈病抗病的分子机制奠定基础，同时为抗病育种提供理论依据。

玉米南方锈病是玉米生产上普遍发生的真菌性病害。已有研究表明，在玉米第10染色体短臂上存在一个抗病基因富集区。然而，由于该区域基因组结构的复杂性，迄今还没有克隆出抗病基因的报道。课题组前期研究在对该区域鉴定到一个主效抗病QTL(RppCML496)，并初步定位在274Kb的范围内。本研究采用近等基因系作图群体，通过抗病区域内分子标记开发和交换单株筛选，把抗病基因限定在45Kb的范围内；在该抗病区域内，利用生物信息学方法对该区域进行基因预测，共鉴定出4个与抗病相关的候选基因；结合预测基因在抗、感亲本和突变体间的序列差异筛选，鉴定出NLR3是抗病QTL的候选基因；本项目的实施为解析玉米南方锈病抗病的分子机制奠定基础，同时为抗病育种提供理论依据。