Response of Cold Region Alfalfa Ecotypes to Peronospora trifoliorum de Bary, the Causal Fungus of Downy Mildew

To study the relative resistance of alfalfa cold region ecotypes to downy mildew disease, an experiment was carried out with four replications in RCBD with 15 treatments including 13 alfalfa cold ecotypes, one moderately susceptible ecotype (Yazdi) and one moderately resistant ecotype (Nikshahri) as controls in three locations Hamedan, Gorgan and Zanjan (field test in natural conditions) and Karaj (greenhouse test), in 2008. The results of field experiment showed that ecotypes Yazdi and Hamedani with 67.4% and 55.3% mean disease severity (DS), respectively were susceptible, Ecotype Nikshahri with 18.4% was resistant and ecotypes Malek Kandi and Ghargholoogh with 26.8% and 26.3% DS, respectively were moderately resistant. The results of greenhouse experiment were similar to those of the field experiment where ecotypes Yazdi and Hamedani were assessed as susceptible and ecotypes Nikshahri, Ramandi and Ghargholoogh were resistant. In the light of these results, the resistant and moderately resistant ecotypes which also performed high yield and favorable agronomic characteristics can be selected for more investigation towards cultivar release.