Powdery mildew isa major disease of barley (Hordeum vulgare L.) for which breeders have traditionally relied on dominant, pathogen race-specific resistance genes for genetic control. Directional selection pressures in extensive monocultures invariably result in such genes being overcome as the pathogen mutates to evade recognition. This has led to a widespread reliance on fungicides and a single broad-spectrum recessive resistance provided by the mlo gene. The range of resistance genes and alleles found in wild crop relatives and landraces has been reduced in agricultural cultivars through an erosion of genetic diversity during domestication and selective breeding. Three novel major-effect adult plant resistance (APR) genes from landraces, designated Resistance to Blumeria graminis f. sp. hordei (Rbgh1 to Rbgh3), were identified in the terminal regions of barley chromosomes 5HL, 7HS, and 1HS, respectively. The phenotype of the new APR genes showed neither pronounced penetration resistance, nor the spontaneous necrosis and mesophyll cell death typical of mlo resistance, nor a whole epidermal cell hypersensitive response, typical of race-specific resistance. Instead, resistance was localized to the site of attempted penetration in an epidermal cell and was associated with cell wall appositions and cytosolic vesicle-like bodies, and lacked strong induction of reactive oxygen species. The APR genes exhibited differences in vesicle-like body sizes, their distribution, and the extent of localized 3,3-diaminobenzidine staining in individual doubled haploid lines. The results revealed a set of unique basal penetration resistance genes that offer opportunities for combining different resistance mechanisms in breeding programs for robust mildew resistance.

中文翻译：

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大麦白粉病成虫抗性基因赋予与广谱抗性相关的基础穿透抗性

白粉病是大麦 ( Hordeum vulgare L.) 的一种主要病害，育种者传统上依赖显性的病原体种族特异性抗性基因进行遗传控制。广泛单一培养中的定向选择压力总是导致这些基因被克服，因为病原体发生突变以逃避识别。这导致了对杀菌剂的广泛依赖和mlo基因提供的单一广谱隐性抗性。通过驯化和选择性育种过程中遗传多样性的侵蚀，在野生作物近缘种和地方品种中发现的抗性基因和等位基因的范围在农业品种中已经减少。来自地方品种的三个新的主要影响成年植物抗性（APR）基因，命名为R对B lumeria g raminis f 的抗性。sp。h ordei ( Rbgh1至Rbgh3 ) 分别在大麦染色体 5HL、7HS 和 1HS 的末端区域中被鉴定。新的 APR 基因的表型既没有表现出明显的穿透阻力，也没有表现出mlo典型的自发坏死和叶肉细胞死亡抗性，也不是整个表皮细胞的过敏反应，典型的种族特异性抗性。相反，抗性局限于表皮细胞中试图穿透的部位，并与细胞壁附着和细胞溶质囊泡样体有关，并且缺乏对活性氧的强烈诱导。APR 基因在个体双倍单倍体系中表现出囊泡样体型、分布和局部 3,3-二氨基联苯胺染色程度的差异。结果揭示了一组独特的基础穿透抗性基因，这些基因为在育种计划中结合不同的抗性机制以实现强大的霉变抗性提供了机会。