Clubroot is one of the most important diseases for many important cruciferous vegetables and oilseed crops worldwide. Different clubroot resistance (CR) loci have been identified from only limited species in Brassica, making it difficult to compare and utilize these loci. European fodder turnip ECD04 is considered one of the most valuable resources for CR breeding. To explore the genetic and evolutionary basis of CR in ECD04, we sequenced the genome of ECD04 using de novo assembly and identified 978 candidate R genes. Subsequently, the 28 published CR loci were physically mapped to 15 loci in the ECD04 genome, including 62 candidate CR genes. Among them, two CR genes, CRA3.7.1 and CRA8.2.4, were functionally validated. Phylogenetic analysis revealed that CRA3.7.1 and CRA8.2.4 originated from a common ancestor before the whole-genome triplication (WGT) event. In clubroot susceptible Brassica species, CR-gene homologues were affected by transposable element (TE) insertion, resulting in the loss of CR function. It can be concluded that the current functional CR genes in Brassica rapa and non-functional CR genes in other Brassica species were derived from a common ancestral gene before WGT. Finally, a hypothesis for CR gene evolution is proposed for further discussion.

中文翻译：

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R 基因三倍体赋予欧洲饲料萝卜以改善的根肿病抗性

根肿病是全世界许多重要的十字花科蔬菜和油料作物最重要的病害之一。仅从芸苔属的有限物种中鉴定出不同的根肿病抗性 (CR) 基因座，因此难以比较和利用这些基因座。欧洲饲料萝卜 ECD04 被认为是 CR 育种最有价值的资源之一。为了探索 ECD04 中 CR 的遗传和进化基础，我们使用从头组装对 ECD04 的基因组进行了测序，并鉴定了 978 个候选 R 基因。随后，将 28 个已发表的 CR 位点物理映射到 ECD04 基因组中的 15 个位点，包括 62 个候选 CR 基因。其中，两个CR基因，CRA3.7.1和CRA8.2.4, 进行了功能验证。系统发育分析表明，CRA3.7.1和CRA8.2.4在全基因组三倍体 (WGT) 事件之前起源于一个共同祖先。在根肿病易感的芸苔属植物中，CR 基因同源物受到转座因子 (TE) 插入的影响，导致 CR 功能丧失。可以得出结论，目前白菜中的功能性 CR 基因和其他芸苔属物种中的非功能性 CR 基因来源于 WGT 之前的共同祖先基因。最后，提出了CR基因进化的假设以供进一步讨论。