Leaf rust (also called brown rust) in wheat, caused by fungal pathogen Puccinia triticina Erikss. (Pt) is one of the major constraints in wheat production worldwide. Pt is widespread with diverse population structure and undergoes rapid evolution to produce new virulent races against resistant cultivars that are regularly developed to provide resistance against the prevailing races of the pathogen. Occasionally, the disease may also take the shape of an epidemic in some wheat-growing areas causing major economic losses. In the recent past, substantial progress has been made in characterizing the sources of leaf rust resistance including non-host resistance (NHR). Progress has also been made in elucidating the population biology of Pt and the mechanisms of wheat-Pt interaction. So far, ∼80 leaf rust resistance genes (Lr genes) have been identified and characterized; some of them have also been used for the development of resistant wheat cultivars. It has also been shown that a gene-for-gene relationship exists between individual wheat Lr genes and the corresponding Pt Avr genes so that no Lr gene can provide resistance unless the prevailing race of the pathogen carries the corresponding Avr gene. Several Lr genes have also been cloned and their products characterized, although no Avr gene corresponding a specific Lr gene has so far been identified. However, several candidate effectors for Pt have been identified and functionally characterized using genome-wide analyses, transcriptomics, RNA sequencing, bimolecular fluorescence complementation (BiFC), virus-induced gene silencing (VIGS), transient expression and other approaches. This review summarizes available information on different aspects of the pathogen Pt, genetics/genomics of leaf rust resistance in wheat including cloning and characterization of Lr genes and epigenetic regulation of disease resistance.

中文翻译：

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小麦叶锈病研究进展

小麦中的叶锈病（也称为褐锈病），由真菌病原体 Puccinia triticina Erikss 引起。(Pt) 是全球小麦生产的主要制约因素之一。Pt 分布广泛，具有多样化的种群结构，并经过快速进化以产生针对抗性栽培品种的新毒性品种，这些品种定期开发以提供对病原体主要品种的抗性。有时，这种疾病也可能在一些小麦种植区形成流行病，造成重大经济损失。最近，在表征包括非寄主抗性 (NHR) 在内的叶锈病抗性来源方面取得了重大进展。在阐明 Pt 的种群生物学和小麦-Pt 相互作用机制方面也取得了进展。迄今为止，已经鉴定和表征了~80个叶锈病抗性基因（Lr基因）；其中一些还被用于开发抗性小麦品种。还表明，单个小麦 Lr 基因和相应的 Pt Avr 基因之间存在基因对基因的关系，因此除非病原体的主要种族携带相应的 Avr 基因，否则任何 Lr 基因都不能提供抗性。一些 Lr 基因也已被克隆并表征了它们的产品，尽管迄今为止尚未鉴定出与特定 Lr 基因相对应的 Avr 基因。然而，已经使用全基因组分析、转录组学、RNA 测序、双分子荧光互补 (BiFC)、病毒诱导的基因沉默 (VIGS)、瞬时表达和其他方法鉴定了 Pt 的几种候选效应物并对其进行了功能表征。