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.在防控小麦壳针孢叶斑病（Septoria tritici blotch, STB）方面，数量抗性（Quantitative resistance）相较主效基因抗性（major gene resistance）往往更具持久性。此前有研究提出假说：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（pycnidia）密度衡量的、影响病原菌繁殖的抗性，二者存在显著差异。本研究利用335份欧洲优质冬小麦品种组成的种质群体，在设置重复的田间试验中，让其自然侵染多样化的小麦壳针孢菌（Zymoseptoria tritici）种群，以此验证上述假说。本研究对21420张扫描后的小麦叶片开展自动图像分析（automated image analysis, AIA），获取了精确、客观且可重复的条件性STB发病强度定量指标。这些指标使我们能够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，证实这两类抗性性状在很大程度上相互独立。以寄主受害程度为依据的品种排名，与以病原菌繁殖水平为依据的品种排名存在显著差异，这表明在旨在提升STB抗性的小麦育种项目中，应当分别考量这两类抗性。我们提出假说：这两类不同的抗性分别受不同的遗传机制调控，因此可以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，基于自动图像分析的品种排名与传统目视评分的品种排名之间存在显著相关性，这表明自动图像分析可作为传统STB抗性测定方法（主要基于寄主受害程度）的补充手段，同时能够更精准地测定病原菌繁殖水平。本研究证实，作物生长季早期的病原菌繁殖水平测定指标，是预测生长季后期寄主受害程度的最佳指标，这阐明了在育种中选择可降低病原菌繁殖的抗性性状的重要性，以最大限度减少STB造成的产量损失。目前，该数据集已可用于育种项目，研究人员可依据不同的抗性类别，筛选出对自然存在的多样化Z. tritici种群具有广谱抗性的小麦品种。