Powdery mildews are obligate biotrophic fungal pathogens causing important diseases of plants worldwide. Very little is known about the requirements for their pathogenicity at the molecular level. This is largely due to the inability to culture these organisms in vitro or to modify them genetically. Here, we describe a mutagenesis procedure based on ultraviolet (UV) irradiation to accumulate mutations in the haploid genome of the barley powdery mildew pathogen Blumeria graminis f. sp. hordei. Exposure of B. graminis f. sp. hordei conidia to different durations of UV-C radiation (10 s to 12 min) resulted in a reduced number of macroscopically visible fungal colonies. B. graminis f. sp. hordei colony number was negatively correlated with exposure time and the total number of consecutive cycles of UV irradiation. Dark incubation following UV exposure further reduced fungal viability, implying that photoreactivation is an important component of DNA repair in B. graminis f. sp. hordei. After several rounds of UV mutagenesis, we selected two mutant isolates in addition to the parental B. graminis f. sp. hordei K1 isolate for whole-genome resequencing. By combining automated prediction of sequence variants and their manual validation, we identified unique UV-induced mutations in the genomes of the two isolates. Most of these mutations were in the up- or downstream regions of genes or in the intergenic space. Some of the variants detected in genes led to predicted missense mutations. As an additional insight, our bioinformatic analyses revealed a complex population structure within supposedly clonal B. graminis f. sp. hordei isolates.

白粉病是专性的生物营养真菌病原体，引起全世界范围内的重要植物病害。在分子水平上对其致病性的要求知之甚少。这主要是由于无法体外培养这些生物或无法对其进行遗传修饰。在这里，我们描述了一种诱变程序，该程序基于紫外线（UV）辐射来积累大麦白粉病病原体Blumeria graminis f的单倍体基因组中的突变。sp。大麦。B. graminis的接触f。sp。霍尔迪分生孢子对UV-C辐射的不同持续时间（10 s至12分钟）导致肉眼可见的真菌菌落数量减少。B.格拉米尼斯f。sp。霍尔迪菌落数与暴露时间和紫外线照射的连续循环总数负相关。紫外线暴露后的黑暗孵育进一步降低了真菌的活力，这表明光再活化是小麦芽孢杆菌DNA修复的重要组成部分。sp。大麦。经过几轮紫外线诱变后，我们选择了除了亲本芽孢杆菌f。之外的两个突变株。sp。霍尔迪K1分离株用于全基因组重测序。通过结合序列变体的自动预测及其手动验证，我们确定了两个分离株的基因组中独特的紫外线诱导的突变。这些突变大多数在基因的上下游区域或基因间空间中。基因中检测到的一些变异导致了预测的错义突变。作为进一步的见解，我们的生物信息学分析显示，在所谓的无性芽孢杆菌f。B.内存在复杂的种群结构。sp。部落分离物。