Table_7_Natural Variation in Elicitation of Defense-Signaling Associates to Field Resistance Against the Spot Blotch Disease in Bread Wheat (Triticum aestivum L.).XLSX

Spot blotch, caused by the hemibiotropic fungus Bipolaris sorokiniana, is amongst the most damaging diseases of wheat. Still, natural variation in expression of biochemical traits that determine field resistance to spot blotch in wheat remain unaddressed. To understand how genotypic variations relate to metabolite profiles of the components of defense-signaling and the plant performance, as well as to discover novel sources of resistance against spot blotch, we have conducted field studies using 968 wheat genotypes at 5 geographical locations in South-Asia in 2 years. 46 genotypes were identified as resistant. Further, in independent confirmatory trials in subsequent 3 years, over 5 geographical locations, we re-characterized 55 genotypes for their resistance (above 46 along with Yangmai#6, a well characterized resistant genotype, and eight susceptible genotypes). We next determined time-dependent spot blotch-induced metabolite profiles of components of defense-signaling as well as levels of enzymatic components of defense pathway (such as salicylic acid (SA), phenolic acids, and redox components), and derived co-variation patterns with respect to resistance in these 55 genotypes. Spot blotch-induced SA accumulation was negatively correlated to disease progression. Amongst phenolic acids, syringic acid was most strongly inversely correlated to disease progression, indicating a defensive function, which was independently confirmed. Thus, exploring natural variation proved extremely useful in determining traits influencing phenotypic plasticity and adaptation to complex environments. Further, by overcoming environmental heterogeneity, our study identifies germplasm and biochemical traits that are deployable for spot blotch resistance in wheat along South-Asia.

由半营养型真菌（hemibiotropic fungus）平脐蠕孢菌（Bipolaris sorokiniana）引起的小麦斑点病，是小麦生产中危害最严重的病害之一。然而，目前决定小麦田间抗斑点病能力的生化性状表达的自然变异，仍未得到充分解析。为阐明基因型变异与防御信号通路组分代谢谱、植株生长表现之间的关联，并挖掘抗小麦斑点病的新抗病资源，本研究于两年内，在南亚5个地理区域开展田间试验，共纳入968份小麦基因型材料，最终筛选得到46份抗病基因型。在此基础上，研究团队在后续3年间开展了独立验证试验，覆盖5个地理区域，对55份基因型的抗病性进行了重新鉴定——其中包含上述46份抗病种质、已被充分表征的抗病基因型扬麦6号（Yangmai#6），以及8份感病基因型。随后，本研究针对这55份基因型，测定了小麦在斑点病诱导下的防御信号通路组分的时序代谢谱，以及防御通路酶类组分（如水杨酸（salicylic acid, SA）、酚酸类物质及氧化还原组分）的含量，并解析了这些性状与抗病性之间的共变异模式。研究发现，斑点病诱导的水杨酸积累量与病害进程呈显著负相关；在酚酸类物质中，丁香酸（syringic acid）与病害进程的负相关程度最强，提示其具有抗病防御功能，该结论已得到独立验证。综上，挖掘自然变异可为解析影响表型可塑性及复杂环境适应性的性状提供极具价值的研究路径。本研究通过克服环境异质性，鉴定出可用于南亚地区小麦抗斑点病育种的种质资源及生化标记性状。