芥菜型油菜苗期氮效率相关性状全基因组关联分析

Genome-Wide Association Study of Nitrogen Efficiency Related Traits at Seedling Stage in Brassica juncea

【目的】通过对芥菜型油菜苗期氮效率相关性状进行全基因组关联分析,挖掘与油菜氮效率相关性状显著关联的SNP位点,预测相关候选基因,为揭示油菜氮高效分子机制和创制氮高效种质提供理论依据。【方法】以153份芥菜型油菜品系作为关联群体,设置低氮和正常氮2个处理,每个处理设置3个重复,并在2年(2021和2022年)进行2次完全重复的营养液培养试验。计算植株根冠比和地上部氮含量的相对值(低氮/正常氮),以此作为氮效率相关性状进行全基因组关联分析(genome-wide association study,GWAS),挖掘氮效率相关候选基因。【结果】芥菜型油菜氮效率相关性状表现出丰富的变异,变异幅度为0.21—2.44,变异系数为22.92%—26.19%。全基因组关联分析检测到45个显著关联的SNP位点,其中,第一次根冠比相对值(relative root-shoot ratio 1,RRSR1)和第二次根冠比相对值(relative root-shoot ratio 2,RRSR2)共同关联到的显著SNP位点有16个,这些位点可解释的表型变异率为10.69%—15.39%。第一次地上部相对氮含量(relative shoot nitrogen concentration 1,RSNC1)和第二次地上部相对氮含量(relative shoot nitrogen concentration 2,RSNC2)共同关联到的显著SNP位点共有29个,可解释的表型变异率为13.22%—23.96%。在显著SNP位点上下游200 kb范围内共筛选出15个与氮效率相关候选基因,包括5个与硝酸盐转运相关的基因(BjuNPF5.8、BjuNRT2.7、BjuNPF2.3、BjuCLCb和BjuNRT1.3)、3个与氮代谢相关的基因(BjuASN3、BjuGLU2和BjuADCS)、4个与生长发育相关的基因(BjuCOBL8、BjuPYL6、BjuSAUR72和BjuUP3)和3个与逆境响应相关的基因(BjuNTP7、BjuJUB1和BjuPYL6)。【结论】共检测到45个与氮效率相关性状显著关联的SNP位点,筛选出15个可能与芥菜型油菜氮效率相关的候选基因。

【Objective】The genome-wide association analysis was performed to identify SNP loci significantly associated with nitrogen use efficiency(NUE)traits in Brassica juncea at seedling stage and to predict the relevant candidate genes,providing a theoretical basis for revealing the molecular mechanism of nitrogen use efficiency in rapeseed and creating nitrogen-efficient germplasm.【Method】The population of 153 Brassica juncea resources was used as the analysis population.Two treatments,low N and normal N,were established using three replicates for each treatment,and two replicated nutrient culture trials were conducted over a two-year period(2021 and 2022).The relative values of root-shoot ratio and shoot nitrogen concentration(low/normal N)were calculated and utilized as NUE traits for a genome-wide association study(GWAS)aimed at exploring candidate genes for NUE.【Result】NUE traits of Brassica juncea resources exhibited abundant variation,ranging from 0.21-2.44 with coefficients of variation of 22.92%-26.19%.The GWAS identified 45 significant SNP loci,among which 16 overlapped between the first relative root-shoot ratio(RRSR1)and the second relative root-shoot ratio(RRSR^(2)),accounting for a phenotype variance range of 10.69%-15.39%.Additionally,29 significant SNP loci were shared between the first relative shoot nitrogen concentration(RSNC1)and the second relative shoot nitrogen concentration(RSNC2),explaining a phenotype variance range of 13.22%-23.96%.15 candidate genes for NUE were identified within 200 kb upstream and downstream regions of significant SNP loci,including 5 genes related to nitrate transport(BjuNPF5.8,BjuNRT2.7,BjuNPF2.3,BjuCLCb and BjuNRT1.3),3 genes associated with nitrogen metabolism(BjuASN3,BjuGLU2 and BjuADCS),4 genes involved in plant growth and development(BjuCOBL8,BjuPYL6,BjuSAUR72 and BjuUP3)and 3 genes participated in stress response(BjuNTP7,BjuJUB1 and BjuPYL6).【Conclusion】45 SNP loci were detected significantly associated with NUE traits and 15 candidate genes for NUE were identified in this study.