Wheat blast, caused by Magnaporthe oryzae Triticum (MoT) pathotype, is a global threat to wheat (Triticum aestivum L.) production. Few blast resistance (R) genes have been identified to date, therefore assessing potential sources of resistance in wheat is important. The Brazilian wheat cultivar BR 18-Terena is considered one of the best sources of resistance to blast and has been widely used in Brazilian breeding programmes, however the underlying genetics of this resistance are unknown. BR 18-Terena was used as the common parent in the development of two recombinant inbred line (RIL) F6 populations with the Brazilian cultivars Anahuac 75 and BRS 179. Populations were phenotyped for resistance at the seedling and heading stage using the sequenced MoT isolate BR32, with transgressive segregation being observed. Genetic maps containing 1779 and 1318 markers, were produced for the Anahuac 75 × BR 18-Terena and BR 18-Terena × BRS 179 populations, respectively. Five quantitative trait loci (QTL) associated with seedling resistance, on chromosomes 2B, 4B (2 QTL), 5A and 6A, were identified, as were four QTL associated with heading stage resistance (1A, 2B, 4A and 5A). Seedling and heading stage QTL did not co-locate, despite a significant positive correlation between these traits, indicating that resistance at these developmental stages is likely to be controlled by different genes. BR 18-Terena provided the resistant allele for six QTL, at both developmental stages, with the largest phenotypic effect conferred by a QTL being 24.8% suggesting that BR 18-Terena possesses quantitative resistance. Haplotype analysis of 100 Brazilian wheat cultivars indicates that 11.0% of cultivars already possess a BR 18-Terena-like haplotype for more than one of the identified heading stage QTL. This study suggests that BR 18-Terena possesses quantitative resistance to wheat blast, with nine QTL associated with resistance at either the seedling or heading stage being detected. Wheat blast resistance is also largely tissue-specific. Identification of durable quantitative resistances which can be combined with race-specific R gene-mediated resistance is critical to effectively control wheat blast. Collectively, this work facilitates marker-assisted selection to develop new varieties for cultivation in regions at risk from this emerging disease.

中文翻译：

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剖析了巴西小麦品种BR 18-Terena中小麦瘟病抗性的遗传基础。

由稻瘟病菌（Magnaporthe oryzae Triticum）（MoT）致病型引起的小麦爆炸是对小麦（Triticum aestivum L.）生产的全球威胁。迄今为止，几乎没有鉴定出稻瘟病抗性（R）基因，因此评估小麦中潜在的抗性来源很重要。巴西小麦品种BR 18-Terena被认为是抗稻瘟病的最佳来源之一，已在巴西育种计划中得到广泛使用，但是这种抗性的基本遗传基因尚不清楚。BR 18-Terena被用作开发两个带有巴西品种Anahuac 75和BRS 179的重组自交系（RIL）F6群体的共同亲本。使用测序的MoT分离株BR32在育苗和抽穗期对群体进行抗性表型分析，并观察到过分的隔离。分别为Anahuac 75×BR 18-Terena和BR 18-Terena×BRS 179种群绘制了包含1779和1318标记的遗传图谱。在染色体2B，4B（2 QTL），5A和6A上鉴定了五个与幼苗抗性相关的数量性状基因座（QTL），以及与抽穗期抗性相关的四个QTL（1A，2B，4A和5A）。尽管这些性状之间的显着正相关，但苗期和抽穗期的QTL并没有共存，表明在这些发育阶段的抗性很可能由不同的基因控制。BR 18-Terena在两个发育阶段均提供了六个QTL的抗性等位基因，QTL赋予的最大表型效应为24.8％，表明BR 18-Terena具有定量抗性。对100个巴​​西小麦品种的单倍型分析表明，对于超过一个已确定的抽穗期QTL，已有11.0％的品种已经具有BR 18-Terena样单倍型。这项研究表明，BR 18-Terena对小麦瘟病具有定量抗性，其中有9个QTL与苗期或抽穗期的抗性有关。小麦瘟病抗性在很大程度上也是组织特异性的。鉴定可以与种族特异性R基因介导的抗性结合的持久定量抗性对于有效控制小麦瘟病至关重要。总的来说，这项工作促进了标记辅助选择，以开发新品种，以便在有这种新病风险的地区种植。0％的品种已经具有超过一个已确定的抽穗期QTL的BR 18-Terena样单倍型。这项研究表明，BR 18-Terena对小麦瘟病具有定量抗性，其中有9个QTL与苗期或抽穗期的抗性有关。小麦瘟病抗性在很大程度上也是组织特异性的。可以与种族特异性R基因介导的抗性相结合的持久定量抗性的鉴定对于有效控制小麦瘟病至关重要。总的来说，这项工作促进了标记辅助选择，以开发新品种，以便在有这种新病风险的地区种植。0％的品种已经具有超过一个已确定的抽穗期QTL的BR 18-Terena样单倍型。这项研究表明，BR 18-Terena对小麦瘟病具有定量抗性，其中有9个QTL与苗期或抽穗期的抗性有关。小麦瘟病抗性在很大程度上也是组织特异性的。可以与种族特异性R基因介导的抗性相结合的持久定量抗性的鉴定对于有效控制小麦瘟病至关重要。总的来说，这项工作促进了标记辅助选择，以开发新品种，以便在有这种新病风险的地区种植。在苗期或抽穗期检测到与抗性相关的9个QTL。小麦瘟病抗性在很大程度上也是组织特异性的。可以与种族特异性R基因介导的抗性相结合的持久定量抗性的鉴定对于有效控制小麦瘟病至关重要。总的来说，这项工作促进了标记辅助选择，以开发新品种，以便在有这种新病风险的地区种植。在苗期或抽穗期检测到与抗性相关的9个QTL。小麦瘟病抗性在很大程度上也是组织特异性的。可以与种族特异性R基因介导的抗性相结合的持久定量抗性的鉴定对于有效控制小麦瘟病至关重要。总的来说，这项工作促进了标记辅助选择，以开发新品种，以便在有这种新病风险的地区种植。