Table_5_Multi-Location Evaluation of Global Wheat Lines Reveal Multiple QTL for Adult Plant Resistance to Septoria Nodorum Blotch (SNB) Detected in Specific Environments and in Response to Different Isolates.DOCX

The slow rate of genetic gain for improving resistance to Septoria nodorum blotch (SNB) is due to the inherent complex interactions between host, isolates, and environments. Breeding for improved SNB resistance requires evaluation and selection of wheat genotypes consistently expressing low SNB response in different target production environments. The study focused on evaluating 232 genotypes from global origins for resistance to SNB in the flag leaf expressed in different Western Australian environments. The aim was to identify resistant donor germplasm against historical and contemporary pathogen isolates and enhance our knowledge of the genetic basis of genotype-by-environment interactions for SNB response. Australian wheat varieties, inbred lines from Centro Internacional de Mejoramiento de Maiz y Trigo (CIMMYT), and International Center for Agricultural Research in the Dry Areas (ICARDA), and landraces from discrete regions of the world showed low to moderate phenotypic correlation for disease response amongst genotypes when evaluated with historical and contemporary isolates at two locations across 3 years in Western Australia (WA). Significant (P < 0.001) genotype-by-environment interactions were detected regardless of same or different isolates used as an inoculum source. Joint regression analysis identified 19 genotypes that consistently expressed low disease severity under infection with different isolates in multi-locations. The CIMMYT inbred lines, 30ZJN09 and ZJN12 Qno25, were particularly pertinent as they had low SNB response and highest trait stability at two locations across 3 years. Genome wide association studies detected 20 QTL associated with SNB resistance on chromosomes 1A, 1B, 4B, 5A, 5B, 6A, 7A, 7B, and 7D. QTL on chromosomes 1B and 5B were previously reported in similar genomic regions. Multiple QTL were identified on 1B, 5B, 6A, and 5A and detected in response to SNB infection against different isolates and specific environments. Known SnTox-Snn interactions were either not evident or variable across WA environments and SNB response may involve other multiple complex biological mechanisms.

提升小麦对颖枯病（Septoria nodorum blotch, SNB）的抗性时，遗传增益速率缓慢，这源于寄主、病原菌菌株与环境三者间固有的复杂互作关系。针对SNB抗性的育种工作，需要在不同目标生产环境中，持续筛选并鉴定出SNB响应水平较低的小麦基因型。本研究聚焦于对源自全球的232份基因型材料，在西澳大利亚的不同环境下评价其旗叶SNB抗性，研究目标为筛选可应对历史及当代病原菌菌株的抗性供体种质，并加深对SNB响应中基因型-环境互作遗传基础的认知。供试材料涵盖澳大利亚小麦品种、国际玉米小麦改良中心（Centro Internacional de Mejoramiento de Maiz y Trigo, CIMMYT）与国际干旱地区农业研究中心（International Center for Agricultural Research in the Dry Areas, ICARDA）的自交系，以及来自全球不同区域的地方品种。在西澳大利亚两地、连续3年使用历史及当代菌株开展接种评价时，各基因型间的病害响应表型相关性呈低到中等水平。无论接种源采用相同还是不同的菌株，均检测到极显著（P < 0.001）的基因型-环境互作效应。联合回归分析筛选出19份基因型，它们在多地点、不同菌株接种条件下均持续表现出较低的病害严重度。其中，CIMMYT的自交系30ZJN09与ZJN12 Qno25尤为突出，这两份材料不仅SNB响应水平较低，且在3年、两地试验中表现出最高的性状稳定性。全基因组关联研究（Genome Wide Association Studies）共检测到20个与SNB抗性相关的数量性状位点（Quantitative Trait Locus, QTL），分布于1A、1B、4B、5A、5B、6A、7A、7B染色体上。其中1B与5B染色体上的QTL，此前已有研究在相似基因组区域中报道。在1B、5B、6A与5A染色体上共鉴定到多个QTL，这些QTL可响应不同菌株接种以及特定环境下的SNB侵染。已知的SnTox-Snn互作在西澳大利亚的试验环境中要么未被观测到，要么表现出变异；SNB抗性响应可能还涉及其他多种复杂的生物学机制。