甘蓝抗根肿病4号生理小种抗性QTL定位

Recently, cruciferae clubroot, caused by Plasmodiophora brassicae Woron., has spread quickly and has been a serious threat to cabbage production, cultivating disease-resistant varieties is the most effective method to prevent clubroot. In the previous study, the system for evaluation of resistance to clubroot has been constructed in cabbage, 150 cabbage genotypes were subsequently evaluated for seedling resistance to P.brassicae race 4, one cabbage genotypes (7QN8) were identified as highly resistant. Inbred lines 7QN8 and 7Q239, resistance and susceptible respectively, were used to construct F2 and DH segregation populations. Inheritance analysis of F1 can be concluded that there are QTLs with dominant effect controlling clubroot resistance in 7QN8. In the current study, the genetic linkage map is constructed based on F2 and DH populations from cross 7QN8 and 7Q239, plants will be evaluated for clubroot resistance, and inheritance of clubroot resistance will be analyzed in cabbage. QTL-Seq will be used to map genes for clubroot resistance by detecting SNPs. Fine mapping using classical QTL mapping method by constructing secondary mapping populations. Using RNA-Seq, haplotypes analysis to confirm the candidate genes for clubroot resistance. Our research findings are believed to confirm the candidate genes for clubroot resistance, and developing molecular markers closely linked to clubroot resistance genes. These studies will be valuable for cloning of clubroot resistance genes, and also have significant theoretical guidance value towards clubroot resistance breeding in cabbage.

近年来由芸薹根肿菌引起的十字花科根肿病在我国迅速蔓延并严重威胁甘蓝的生产，培育抗病品种是防治根肿病最有效的方法。在此前的研究中，我们建立了一种准确、稳定的甘蓝根肿病鉴定技术体系，利用根肿菌4号生理小种对150份甘蓝的进行根肿病苗期抗性鉴定，鉴定出1份高抗的甘蓝自交系7QN8，并以抗病材料7NQ8和感病材料7Q239为亲本构建了F2群体和DH群体，对F1代进行遗传分析表明7QN8中存在显性的抗根肿病QTL。本项目拟以7QN8/7Q239的F2群体和DH群体为作图群体，鉴定群体的单株抗性，分析根肿病抗性遗传规律，利用QTL-Seq技术检测SNP差异位点进行QTL初定位，通过构建次级群体进行QTL精细定位，结合RNA-Seq表达分析、单倍型分析获得候选抗根肿病基因。预期研究结果可获得甘蓝抗根肿病候选基因，并开发与抗根肿病基因紧密连锁的分子标记，对于指导甘蓝抗根肿病育种有重要的意义。

甘蓝根肿病是由芸薹根肿菌引起的一种世界性的土传病害，严重威胁甘蓝的生产。在此前的研究中，我们鉴定出1份高抗的甘蓝自交系7QN8。本项目研究了7QN8的根肿病抗性遗传规律，对其抗根肿病QTL进行了定位，并利用细胞学与转录组学相结合的方法对7QN8抗根肿病的机理进行了研究。本项目通过对P1、P2、 F1、F2、BC1P1、BC1P2及F2：3群体进行接种鉴定和遗传分析，确定7QN8的抗性遗传模式为加性-显性-上位性多基因遗传。利用F2、F2：3及RIL群体对抗根肿病基因进行QTL定位。通过BSA，发现在C08染色体2~21 Mb的区段内存在控制甘蓝根肿病抗性的QTL位点。随后，在全基因组上开发了153个InDel和SSR标记并构建了9个连锁图谱，结合F2：3、RIL群体的抗性鉴定结果，在7QN8的2号和8号染色体上分别定位到一个抗病QTL，分别命名为qBoCR2.1和qBoCR8.1。它们的物理区间分别为645.7Kb和1.9Mb，贡献率分别为15.6%和7.5%。通过功能注释发现，在C2和C8染色体的QTL区间内分别存在4个和16个抗病相关基因。对7QN8和7Q239的基因组序列比较发现，C2的QTL区间内的候选基因Boc02g03437.1在编码区存在2个SNP的变异。此外，利用光学显微镜和透射电镜对根肿菌侵染7QN8和7Q239的过程进行了观察和比较，结果表明根肿菌的初级和次级侵染过程分别发生在3天和7天，且在整个侵染过程中7Q239中根肿菌的含量要高于7QN8中。利用RNA-seq对根肿菌侵染7QN8和7Q239的不同时间的根部进行转录组测序，结果表明，7天时是根肿菌侵染的关键节点；通过比较分析筛选得到65个可能与抗病相关的基因，并预测了14个根肿菌中的效应子。