Powdery Mildew of Wheat: Research Progress, Opportunities, and Challenges

Powdery mildew caused by the biotrophic fungus Blumeria graminis f. sp. tritici (Bgt) is one of the most important diseases of wheat after three rusts. Recently, wheat powdery mildew has been reported to reduce yield by 10–15% and up to 50% in severe cases. It serves as a model system for studying biotrophic pathogens. It is, therefore, very important to understand etiology, virulence spectrum, genetics of host resistance, and other viable management options to combat this disease. In the direction of host resistance, over 91 Pm resistance genes have been identified so far, with 61 loci mapped to them. Apart from these, new genes are continually being searched and described in common wheat and its different relatives. Quantitative trait locus (QTL) mapping is an effective method of detecting quantitative resistance to powdery mildew. Over 100 Bgt QTLs have been mapped to homologous groups from various molecular mapping studies. New QTL identification is still predicted to boost with the development of a high-resolution genetic map aided by genome-wide markers. Wheat relatives possess untapped diversity for mildew resistance. In this context, interspecific hybridization for introgressing disease resistance genes from wild distant relatives is effective for breeding more resilient cultivars. Linkage drag, fungicidal resistance, fast jump and above all, the changing climate are among the potential challenges for managing powdery mildew. Therefore, there is a need to efficiently explore modern technologies to boost crop improvement in the face of more challenging production conditions in future. Advent of advanced molecular diagnostic techniques for pathogen identification, cultivar development, artificial intelligence algorithms, and speed breeding protocols offer vast opportunities to tackle powdery mildew fungus in future.