Data from: Ranking quantitative resistance to Septoria tritici blotch in elite wheat cultivars using automated image analysis

Quantitative resistance is likely to be more durable than major gene resistance for controlling Septoria tritici blotch (STB) on wheat. Earlier studies hypothesized that resistance affecting the degree of host damage, as measured by the percentage of leaf area covered by STB lesions, is distinct from resistance that affects pathogen reproduction, as measured by the density of pycnidia produced within lesions. We tested this hypothesis using a collection of 335 elite European winter wheat cultivars that was naturally infected by a diverse population of Zymoseptoria tritici in a replicated field experiment. We used automated image analysis (AIA) of 21420 scanned wheat leaves to obtain quantitative measures of conditional STB intesity that were precise, objective, and reproducible. These measures allowed us to explicitly separate resistance affecting host damage from resistance affecting pathogen reproduction, enabling us to confirm that these resistance traits are largely independent. The cultivar rankings based on host damage were different from the rankings based on pathogen reproduction, indicating that the two forms of resistance should be considered separately in breeding programs aiming to increase STB resistance. We hypothesize that these different forms of resistance are under separate genetic control, enabling them to be recombined to form new cultivars that are highly resistant to STB. We found a significant correlation between rankings based on automated image analysis and rankings based on traditional visual scoring, suggesting that image analysis can complement conventional measurements of STB resistance, based largely on host damage, while enabling a much more precise measure of pathogen reproduction. We showed that measures of pathogen reproduction early in the growing season were the best predictors of host damage late in the growing season, illustrating the importance of breeding for resistance that reduces pathogen reproduction in order to minimize yield losses caused by STB. These data can already be used by breeding programs to choose wheat cultivars that are broadly resistant to naturally diverse Z. tritici populations according to the different classes of resistance.

在防治小麦壳针孢叶斑病（Septoria tritici blotch, STB）方面，数量抗性相较于主效基因抗性往往更具持久性。过往研究提出假说：以病斑覆盖叶面积百分比衡量的、影响寄主受害程度的抗性，与以病斑内产生的分生孢子器密度衡量的、影响病原菌繁殖的抗性，二者存在显著差异。本研究依托一项重复田间试验，利用335份欧洲优良冬小麦品种组成的种质集合，在自然感染多样化小麦壳针孢菌（Zymoseptoria tritici）种群的条件下开展验证。通过对21420张扫描获取的小麦叶片进行自动化图像分析（automated image analysis, AIA），我们获取了精准、客观且可重复的条件性STB严重度量化指标。这些指标可明确区分影响寄主受害程度的抗性与影响病原菌繁殖的抗性，证实两类抗性性状在很大程度上相互独立。基于寄主受害程度的品种排名与基于病原菌繁殖水平的品种排名存在显著差异，这表明在旨在提升STB抗性的育种计划中，应分别考量这两类抗性形式。我们推测，这两类不同的抗性受独立的遗传调控，因此可通过基因重组培育出对STB具有高抗性的小麦新品种。本研究发现，自动化图像分析得到的品种排名与传统人工视觉评分的排名存在显著相关性，这说明自动化图像分析可作为以寄主受害程度为主要评估指标的传统STB抗性检测方法的补充手段，同时能更精准地测定病原菌繁殖水平。研究还表明，生长季早期的病原菌繁殖水平量化指标，可最佳预测生长季后期的寄主受害程度，这凸显了在育种中筛选可降低病原菌繁殖的抗性品种的重要性，以最大限度减少STB造成的产量损失。当前，上述数据集已可供育种项目使用，帮助育种者依据不同的抗性类别，筛选出对自然多样化的Z. tritici种群具有广谱抗性的小麦品种。