Investigating the powdery mildew on planted alfalfa in natural resources around Boroujerd, Iran

In this study different characters of powdery mildew of alfalfa were investigated in natural resources around Boroujerd in Lourestan province. The fungi species, disease severity, ascospore as primary inoculums, percent of germination of conidia, chemical analysis of non-infected and infected plants, overwintering manner of fungi and correlation of plant phonologic period with fungi growth organs were studied. The fungi were identified as Leveillula taurica (Lev.) Arnaud. The mean of the disease severity on upper and lower leave surfaces was 12.13± 2.4 and 39.32± 3.81 percent, respectively. Between disease severity on upper and lower surface of leaves there was a positive and significant correlation (r= 46.4) & (p<0.01). Liberation of ascospore increased from bigining of liberation until infection time. It was determined that ascospore was the primary infection source. Also, the best temperature and time for germination of conidia was 100.C and 72 hour and there was not any statistically significant difference between 3 temperatures of 10, 15 and 200.C (p<0.01). Between dried mater and ether extract of non-infected and infected plants there was not any statistical significant differences, but between the crude protein, crude fiber and ash of non-infected and infected plant there was a significant difference (p<0.05). The growth of fungi on plant began 5 days after June. The mean height of plants was 55.25 cm and at green stage of plant and the sexual stages, the growth of fungi completed 6 days after the September when the seeds of plant fell on the ground.