基于大白菜近等基因系的抗根肿病QTL QS_B3.1的验证

Validation of a Quantitative Trait Locus QS_B3.1 for Clubroot Resistance in Near-isogenic Lines of Chinese Cabbage

根肿病是影响大白菜生长发育及其产量的一个重要病害。本研究在前人定位出抗根肿病QTL QS_B3.1的基础上,以相同的抗根肿病芜菁自交系‘Siloga’为供体亲本,大白菜自交系‘91-12A’为受体亲本,通过对回交和自交群体的分子标记前景和背景选择,从BC4F3群体中筛选出遗传背景恢复为‘91-12A’,且只含有QS_B3.1位点的大白菜近等基因系。对BC4F3群体进行根肿病抗性鉴定,抗病植株与感病植株的分离比例为3:1,证明QS_B3.1抗病位点表现为显性单基因遗传。BC4F3群体的QS_B3.1连锁标记分析表明,抗病植株均含有QS_B3.1位点,不含QS_B3.1位点的植株均表现为感病,且QS_B3.1位点缩小在A3染色体的一个2.89 Mb区间内。这一发现为今后芸薹属作物的抗根肿病品种的选育以及该基因的精细定位和克隆提供了有力的依据。

Clubroot d isease is one of the most severe disease that can affect the growth and yield of Chinese cabbage. In the previous study, a QTL QS_B3.1 for clubroot resistance was identified in a turnip inbred line‘Siloga'.In this study,‘Siloga'was used as donor parent for integration of QS_B3.1 into Chinese cabbage inbred line‘91-12A'. Based on the advanced backcross program and marker-assisted selection, near-isogenic lines(NILs) of Chinese cabbage containing homozygous QS_B3.1 were selected from BC4F3 population. Clubroot resistant test and marker genotype assay of BC4F3 population indicated that individuals containing QS_B3.1 showed resistance to clubroot disease, while the individuals without QS_B3.1 were shown susceptible. The ratio of resistance to susceptible individuals was 3:1, indicating that the clubroot resistance locus QS_B3.1 was inherited as a single dominant gene. Eventually, QS_B3.1 was narrowed down in a range of 2.89 Mb in A3 chromosome. Our result provides a prerequisite for breeding clubroot resistant cultivars of Chinese cabbage and other Brassica crops, and map-based cloning of this gene.