The bread-making quality of wheat depends on the viscoelastic properties of the dough in which gluten proteins play an important role. The quality of gluten proteins is influenced by the genetics of the different wheat varieties and environmental factors. Occasionally, a near complete loss of gluten strength, measured as the maximum resistance towards stretching (R_max), is observed in grain lots of Norwegian wheat. It is hypothesized that the loss of gluten quality is caused by degradation of gluten proteins by fungal proteases. To identify fungi associated with loss of gluten strength, samples from a selection of wheat grain lots with weak gluten (n = 10, R_max < 0.3 N) and strong gluten (n = 10, R_max ≥ 0.6 N) was analyzed for the abundance of fungal operational taxonomic units (OTUs) using DNA metabarcoding of the nuclear ribosomal Internal Transcribed Spacer (ITS) region ITS1. The DNA quantities for a selection of fungal pathogens of wheat, and the total amount of fungal DNA, were analyzed by quantitative PCR (qPCR). The mean level of total fungal DNA was higher in grain samples with weak gluten compared to grain samples with strong gluten. Heightened quantities of DNA from fungi within the Fusarium Head Blight (FHB) complex, i.e. Fusarium avenaceum, Fusarium graminearum, Microdochium majus, and Microdochium nivale, were observed in grain samples with weak gluten compared to those with strong gluten. Microdochium majus was the dominant fungus in the samples with weak gluten. Stepwise regression modeling based on different wheat quality parameters, qPCR data, and the 35 most common OTUs revealed a significant negative association between gluten strength and three OTUs, of which the OTU identified as M. majus was the most abundant. The same analysis also revealed a significant negative relationship between gluten strength and F. avenaceum detected by qPCR, although the DNA levels of this fungus were low compared to those of M. majus. In vitro growth rate studies of a selection of FHB species showed that all the tested isolates were able to grow with gluten as a sole nitrogen source. In addition, proteins secreted by these fungi in liquid cultures were able to hydrolyze gluten substrate proteins in zymograms, confirming their capacity to secrete gluten-degrading proteases. The identification of fungi with potential to influence gluten quality can enable the development of strategies to minimize future problems with gluten strength in food-grade wheat.

小麦的面包制作质量取决于面团的粘弹性质，其中面筋蛋白起着重要的作用。面筋蛋白的质量受不同小麦品种的遗传和环境因素影响。有时，在挪威小麦的籽粒中观察到面筋强度几乎完全丧失，以最大抗拉伸性（R _max）衡量。假设面筋质量的损失是由真菌蛋白酶降解面筋蛋白引起的。为了鉴定与面筋强度丧失相关的真菌，从面筋弱（n = 10，R _max  <0.3 N）和面筋强（n = 10，R _max）的小麦籽粒中选择样品 使用核糖体内部转录间隔子（ITS）区域ITS1的DNA元条形码，对≥0.6 N）的真菌操作分类单位（OTU）进行了分析。通过定量PCR（qPCR）分析了用于选择小麦真菌病原体的DNA量以及真菌DNA的总量。与具有强筋蛋白的谷物样品相比，具有弱筋蛋白的谷物样品中总真菌DNA的平均水平更高。在面筋弱的谷物样品中，与面筋强的谷物样品相比，镰刀镰刀菌（Fusarium avenaceum），禾谷镰刀菌，细小球藻和微短孢子霉的真菌中的真菌DNA含量增加。桃金娘是面筋弱的样品中的主要真菌。基于不同小麦品质参数，qPCR数据和35个最常见OTU的逐步回归模型显示，面筋强度与三个OTU之间存在显着的负相关性，其中OTU被确定为Ma。majus最丰富。相同的分析还显示，通过qPCR检测到的麸质强度与燕麦曲霉之间存在显着的负相关关系，尽管该真菌的DNA水平低于毛果分支杆菌。。对某些FHB种类的体外生长速率研究表明，所有测试的分离株都能够以面筋作为唯一的氮源生长。此外，这些真菌在液体培养物中分泌的蛋白能够水解酶谱图中的面筋底物蛋白，从而证实了它们分泌降解面筋的蛋白酶的能力。鉴定具有潜在影响面筋质量的真菌，可以开发出策略，以最大限度地减少食品级小麦中面筋强度的未来问题。