Clubroot is a soil-borne disease in cabbage (Brassica oleracea L.) caused by Plasmodiophora brassicae, which poses a great threat to cabbage production. However, clubroot resistance (CR) genes in Brassica rapa could be introduced into the cabbage via breeding to make it clubroot resistant. In this study, CR genes from B. rapa were introduced into the cabbage genome and the mechanism of gene introgression was explored. Two methods were used to create CR materials: 1) The fertility of CR Ogura CMS cabbage germplasms containing CRa was restored by using an Ogura CMS restorer. After cytoplasmic replacement and microspore culture, CRa-positive microspore individuals were obtained. 2) Distant hybridization was performed between cabbage and B. rapa, which contained three CR genes (CRa, CRb and Pb8.1). Finally, BC2 individuals containing all three CR genes were obtained. Inoculation results showed that both CRa-positive microspore individuals and BC2 individuals containing three CR genes were resistant to race 4 of P. brassicae. Sequencing results from CRa-positive microspore individuals with specific molecular markers and genome-wide association study (GWAS) showed penetration at the homologous position of the cabbage genome by a 3.42 Mb CRa containing fragment from B. rapa; indicating homoeologous exchange (HE) as the theoretical basis for the introgression of CR resistance. The successful introduction of CR into the cabbage genome in the present study can provide useful clues for creating introgression lines within other species of interest.

中文翻译：

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基于同源交换的根肿病抗性基因渗入白菜甘蓝

根肿病是由甘蓝根肿菌引起的甘蓝土传病害，对甘蓝生产造成极大威胁。然而，白菜中的抗根肿病（CR）基因可以通过育种引入到卷心菜中，使其具有抗根肿病能力。本研究将白菜CR基因引入甘蓝基因组，并探讨基因渗入机制。使用两种方法来创建 CR 材料： 1) 使用 Ogura CMS 恢复剂恢复含有 CRa 的 CR Ogura CMS 甘蓝种质的育性。经过胞质置换和小孢子培养，获得CRa阳性小孢子个体。2)甘蓝与白菜进行远缘杂交，白菜含有3个CR基因(CRa、CRb和Pb8.1)。最终获得含有全部三个CR基因的BC2个体。接种结果表明，CRa阳性小孢子个体和含有3个CR基因的BC2个体均对甘蓝小种有抗性。具有特定分子标记的 CRa 阳性小孢子个体的测序结果和全基因组关联研究 (GWAS) 显示，含有来自白菜的 3.42 Mb CRa 片段渗透到卷心菜基因组的同源位置；表明同源交换（HE）是CR抗性基因渗入的理论基础。本研究中成功地将 CR 引入卷心菜基因组，可以为在其他感兴趣的物种中创建基因渗入系提供有用的线索。