Research progress on Medicago sativa powdery mildew and its resistance mechanism

Powdery mildew is one of the most widespread plant diseases. It is a fungal disease caused by Erysiphales, and could infect tens of thousands of angiosperms. Medicago sativa is one of the most important forage legumes, which has high nutritional value, high palatability, and strong nitrogen fixation ability. In recent years, with the increase in alfalfa planting density and the overuse of fertilizer, the occurrence of alfalfa powdery mildew has become increasingly severe. For this reason, the symptoms and pathogenic and morbidity conditions of alfalfa powdery mildew were introduced in this study, which lays the foundation for accurate recognition and diagnosis, understanding the regularity of occurrence, timely prevention and treatment of the alfalfa powdery mildew. Meanwhile, the studies on the harm of powdery mildew to alfalfa and the resistance mechanism of alfalfa to powdery mildew were summarized. It was found that the alfalfa powdery mildew commonly occurred and severely endangered the yield and quality of alfalfa. However, few resistance genes were cloned in alfalfa, and research on the resistance mechanism and resistance germplasms were also lacking. Therefore, to solve these problems, this review has proposed combining traditional breeding and modern biotechnology based on an in-depth understanding of the alfalfa resistance mechanism. New resistance genes should be continuously explored and more stable and durable new resistance germplasms should be cultivated. This review aimed to provide references for further study of alfalfa powdery mildew.