Genetic characterization of root architectural traits in barley (Hordeum vulgare L.) germplasm using SNP markers

Increasing attention is paid to providing tools to breeders to underpin targeted breeding for specific root traits that may be useful in low-fertility, drying soils; however, such information is not available for barley (Hordeum vulgare L.). We phenotyped 191 barley accessions from Australia for 26 root and shoot traits using the established semi-hydroponic system, and identified significant variation (CV >=0.25) for 16 of the traits evaluated. The population structure and marker-trait association (MTA) were assessed using 21,061 high-quality genotyping-by-sequencing (GBS)-based single nucleotide polymorphism (SNP) markers. The population structure analysis of the barley panel identified six distinct groups. A total of 435 significant (P <0.001) MTAs were detected with r2 values up to 0.18. The strongest marker-trait associations were found in root length and root dry weight in the top 20 cm, and root volume. Based on physical locations of these MTAs in the barley genome, 33 putative QTL were identified for the root traits, and nine QTL for shoot traits. Among these, seven major QTL shared the same physical regions in the barley genome. The genomic region 640-651 Mb on chromosome 7H was significant for three root traits (lateral root biomass, total root biomass and root biomass in the top 20 cm) and one shoot trait (shoot biomass) and included 440 candidate genes. The putative QTL for various root traits identified in this study would be useful for enhancing adaptation of new barley cultivars to suboptimal environments and abiotic stresses.Keywords: Barley, genotyping-by-sequencing, SNP markers, association mapping, root traits

当前学界愈发重视为作物育种者提供支撑工具，以开展针对低肥力、干旱土壤中具有应用价值的特定根系性状的定向育种；但目前针对大麦（Hordeum vulgare L.）的此类研究数据仍较为匮乏。本研究采用成熟的半水培（semi-hydroponic）系统，对来自澳大利亚的191份大麦种质资源开展26项根系与地上部性状的表型鉴定，结果显示16项被测性状存在显著变异（CV≥0.25）。本研究利用21061个高质量的基于测序分型（genotyping-by-sequencing, GBS）的单核苷酸多态性（single nucleotide polymorphism, SNP）标记，对该群体的群体结构与性状-标记关联（marker-trait association, MTA）进行解析。对该大麦种质集合的群体结构分析共鉴定出6个清晰的遗传类群。共计检测到435个显著（P<0.001）的性状-标记关联，其决定系数r2最高可达0.18。最强的性状-标记关联集中出现在0-20cm土层的根长、根干重以及根体积性状上。基于这些性状-标记关联在大麦基因组中的物理位置，本研究共鉴定出33个调控根系性状的潜在数量性状位点（quantitative trait locus, QTL），以及9个调控地上部性状的潜在QTL。其中7个主效QTL在大麦基因组中共享相同的物理区间。7H染色体上640~651 Mb的基因组区间对3项根系性状（侧根生物量、总根生物量以及0-20cm土层根生物量）以及1项地上部性状（地上部生物量）具有显著调控效应，该区间共包含440个候选基因。本研究鉴定得到的各类根系性状潜在QTL，可用于助力大麦新品种对非适宜环境与非生物胁迫的适应性改良。
关键词：大麦、测序分型（genotyping-by-sequencing, GBS）、单核苷酸多态性标记（SNP markers）、关联作图、根系性状