Evaluation on disease severity index of powdery mildew of sainfoin" Onobrychis viciifoliae L. populations in condition of Khorramabad Lorestan province Iran.

The sainfoin "Onobrychis sativa L." is a forage and rangeland plant which is susceptible to powdery mildews. For surveying of 34 populations to the disease severity of powdery mildew, seeds of populations were planted in research station of Serab Changai, at North West of Khorramabad by 1 2 m plots with 3 replications. The measurement of disease severity of each population was done for each harvest by 3 years. Then the data were analyzed by SAS and then the populations divided to 4 group of tolerant, semi susceptible and susceptible to this disease. According of disease severity index, 34 populations were divided to 22 statistical groups (p<0.05). The population of Polycrass and Oshnavieh with 18 and 19 percent of disease severity had lowest disease severity in comparison with other populations, therefore they evaluated as tolerant groups. Disease severity index of the populations of Khansar2 and Khalkhal were 40 and 37 percent of disease severity and they stand as semi suecceptible group. Another population, were evaluated between this 2 group for disease severity index.