A Method for Selection of Alfalfa Ecotypes Resistant to Downy Mildew Disease

Alfalfa downy mildew, caused by Peronospora trifoliorum, is one of the limiting factors in alfalfa production. Under favorite conditions in spring, the disease is prevalent after first moving and the plant leaves turn to yellow followed by drying. The standard greenhouse experiments and field screening methods are applicable to select the resistant ecotypes of alfalfa to this disease. In greenhouse tests, seven days old seedlings of alfalfa are inoculated with spore suspension. After completion of incubation period and the first symptoms were observed, the percentage of the symptomless seedlings are comparing with resistant control. Field experiments must be carried out for different alfalfa ecotypes in locations with suitable conditions for natural occurrence of disease, using an appropriate statistical design with minimum three replications. The response of cultivars evaluate based on disease severity. In Iran, the cultivars KS224 and Saranac showed resistance to downy mildew and some ecotypes like Kiseverdai, Nikshahri, Gharghlooogh, Malek-Kandi and Gharghloogh known as tolerant to disease.