Jamann Tiffany M, Poland Jesse A, Kolkman Judith M, Smith Laurie G, Nelson Rebecca J
School of Integrative Plant Science, Cornell University, Ithaca, New York 14853.
U.S. Department of Agriculture-Agricultural Research Service, Hard Winter Wheat Genetics Research Unit, Manhattan, Kansas 66502 Department of Agronomy, Kansas State University, Manhattan, Kansas 66506.
Genetics. 2014 Sep;198(1):333-44. doi: 10.1534/genetics.114.167486. Epub 2014 Jul 9.
Multiple disease resistance has important implications for plant fitness, given the selection pressure that many pathogens exert directly on natural plant populations and indirectly via crop improvement programs. Evidence of a locus conditioning resistance to multiple pathogens was found in bin 1.06 of the maize genome with the allele from inbred line "Tx303" conditioning quantitative resistance to northern leaf blight (NLB) and qualitative resistance to Stewart's wilt. To dissect the genetic basis of resistance in this region and to refine candidate gene hypotheses, we mapped resistance to the two diseases. Both resistance phenotypes were localized to overlapping regions, with the Stewart's wilt interval refined to a 95.9-kb segment containing three genes and the NLB interval to a 3.60-Mb segment containing 117 genes. Regions of the introgression showed little to no recombination, suggesting structural differences between the inbred lines Tx303 and "B73," the parents of the fine-mapping population. We examined copy number variation across the region using next-generation sequencing data, and found large variation in read depth in Tx303 across the region relative to the reference genome of B73. In the fine-mapping region, association mapping for NLB implicated candidate genes, including a putative zinc finger and pan1. We tested mutant alleles and found that pan1 is a susceptibility gene for NLB and Stewart's wilt. Our data strongly suggest that structural variation plays an important role in resistance conditioned by this region, and pan1, a gene conditioning susceptibility for NLB, may underlie the QTL.
鉴于许多病原体直接对天然植物种群以及通过作物改良计划间接施加选择压力，多病害抗性对植物适应性具有重要意义。在玉米基因组的1.06号染色体区域发现了一个对多种病原体具有抗性的位点，来自自交系“Tx303”的等位基因对北方叶斑病（NLB）具有数量抗性，对斯图尔特枯萎病具有质量抗性。为了剖析该区域抗性的遗传基础并完善候选基因假说，我们对这两种病害的抗性进行了定位。两种抗性表型均定位于重叠区域，斯图尔特枯萎病的区间被精细定位到一个包含三个基因的95.9 kb片段，北方叶斑病的区间被精细定位到一个包含117个基因的3.60 Mb片段。导入区域几乎没有重组，这表明精细定位群体的亲本自交系Tx303和“B73”之间存在结构差异。我们使用下一代测序数据检查了该区域的拷贝数变异，发现相对于B73的参考基因组，Tx303在该区域的读深度存在很大差异。在精细定位区域，对北方叶斑病的关联分析确定了候选基因，包括一个假定的锌指基因和pan1。我们测试了突变等位基因，发现pan1是北方叶斑病和斯图尔特枯萎病的感病基因。我们的数据有力地表明，结构变异在该区域介导的抗性中起重要作用，而pan1作为北方叶斑病的感病基因，可能是该数量性状位点的基础。
