Jiangsu Key Laboratory of Crop Genetics and Physiology, Jiangsu Co-Innovation Center for Modern Production Technology of Grain Crops, Key Laboratory of Plant Functional Genomics of the Ministry of Education, Jiangsu Key Laboratory of Crop Genomics and Molecular Breeding, Yangzhou University, Yangzhou 225009, China.
International Maize and Wheat Improvement Center (CIMMYT), 06600 Mexico DF, Mexico.
Plant Dis. 2020 Aug;104(8):2210-2216. doi: 10.1094/PDIS-12-19-2584-RE. Epub 2020 Jun 8.
Fusarium head blight (FHB) caused by species is a globally important wheat disease. Host resistance to FHB is composed of multiple mechanisms, including resistance to initial infection (type I), disease spread (type II), toxin accumulation (type III), kernel infection (type IV), and yield loss (type V), of which the last three have been less studied. Traditionally, the -damaged kernel rate (FDK; percentage of -infected grains) from point- or spray-inoculated experiments was used as the parameter for type IV resistance, which may be problematic because of the influence of type II resistance. Here we propose a new definition for type IV resistance: that is, the resistance against infection expressed in wheat grains that have the same chance in contact with the pathogen, under favorable temperature and humidity for infection. confers strong type II resistance, leading to significantly reduced FHB severity and FDK. To investigate the role of in type IV resistance, a pair of near-isogenic lines, R22W ( carrier, resistant in terms of type II resistance) and S22V (non-, susceptible), along with eight wheat genotypes differing at were inoculated at different grain development stages with macrospores both in vivo and in vitro. The in vivo experiments with all florets inoculated demonstrated a significant reduction in thousand kernel weight (TKW) in inoculated grains, regardless of their status and developmental stages. Surprisingly, R22W showed more TKW reduction than S22V, which was supported by the scanning electron microscopy observation that confirmed the more severe degradation of starch granules in R22W grains. The in vitro experiments demonstrated that grains from both R22W and S22V promoted fungal colonization, but no significant difference was found between the two lines. In summary, our results indicated that the proposed type IV evaluation system is effective in determining different grain resistance levels, providing novel tools for FHB resistance breeding. The finding that is not associated with type IV resistance enriches our understanding of this gene.
镰刀菌穗腐病（FHB）由 种引起，是一种全球性重要的小麦病害。宿主对 FHB 的抗性由多种机制组成，包括对初始感染（I 型）、病害扩散（II 型）、毒素积累（III 型）、籽粒感染（IV 型）和产量损失（V 型）的抗性，其中后三种抗性研究较少。传统上，点或喷雾接种实验中 -损伤籽粒率（FDK；受感染籽粒的百分比）被用作 IV 型抗性的参数，但由于 II 型抗性的影响，这可能存在问题。在这里，我们提出了一个新的 IV 型抗性定义：即在有利于感染的温度和湿度下，接触病原菌的小麦籽粒中表达的对 感染的抗性。 赋予了强烈的 II 型抗性，导致 FHB 严重度和 FDK 显著降低。为了研究 在 IV 型抗性中的作用，我们使用了一对近等基因系 R22W（载体，在 II 型抗性方面具有抗性）和 S22V（非载体，敏感），以及 8 个在 位点不同的小麦基因型，在体内和体外用 大型孢子接种不同的籽粒发育阶段。所有小花接种的体内实验表明，无论其 状态和发育阶段如何，接种籽粒的千粒重（TKW）均显著降低。令人惊讶的是，R22W 的 TKW 降低幅度大于 S22V，扫描电子显微镜观察结果证实了 R22W 籽粒中淀粉颗粒的降解更为严重。体外实验表明，来自 R22W 和 S22V 的籽粒均促进了真菌定殖，但两系之间没有发现显著差异。综上所述，我们的结果表明，所提出的 IV 型评价系统在确定不同籽粒抗性水平方面是有效的，为 FHB 抗性育种提供了新的工具。发现 与 IV 型抗性无关丰富了我们对该基因的认识。
