Alleles that confer multiple disease resistance (MDR) are valuable in crop improvement, although the molecular mechanisms underlying their functions remain largely unknown. A quantitative trait locus, qMdr_9.02, associated with resistance to three important foliar maize diseases-southern leaf blight, gray leaf spot and northern leaf blight-has been identified on maize chromosome 9. Through fine-mapping, association analysis, expression analysis, insertional mutagenesis and transgenic validation, we demonstrate that ZmCCoAOMT2, which encodes a caffeoyl-CoA O-methyltransferase associated with the phenylpropanoid pathway and lignin production, is the gene within qMdr_9.02 conferring quantitative resistance to both southern leaf blight and gray leaf spot. We suggest that resistance might be caused by allelic variation at the level of both gene expression and amino acid sequence, thus resulting in differences in levels of lignin and other metabolites of the phenylpropanoid pathway and regulation of programmed cell death.

中文翻译：

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编码玉米咖啡酰-CoA O-甲基转移酶的基因赋予对多种病原体的定量抗性。

赋予多重抗病性（MDR）的等位基因在作物改良中很有价值，尽管其功能所基于的分子机制仍然未知。在玉米9号染色体上鉴定了一个定量性状基因座qMdr _9.02，它与三种重要的叶面玉米病抗性相关：南方叶枯病，灰色叶斑病和北部叶枯病-通过精细定位，关联分析，表达分析，插入诱变和转基因验证，我们证明ZmCCoAOMT2是qMdr _9.02中的基因，它编码与苯丙氨酸途径和木质素产生相关的咖啡酰-CoA O-甲基转移酶赋予对南方叶枯病和灰色叶斑的定量抗性。我们建议耐药性可能是由于基因表达和氨基酸序列水平上的等位基因变异引起的，从而导致木质素和苯丙烷途径的其他代谢产物水平的差异以及对程序性细胞死亡的调节。