2Imam khomeini international university, Qazvin, Iran
3Qazvin Agriculture and Natural Resources Research Center, Qazvin, Iran
Powdery mildew is one of the most important disease concerns of tomato production in different regions of the world, which is caused by different species of Erysiphales. The most important causal agents of which are Leveillula taurica and Oidium neolycopersici. In the present study tomato farms in Qazvin province were surveyed and tomato leaves with powdery mildew symptoms were collected. After morphological studies in laboratory and using reliable resources, the causal agent of tomato powdery mildew was identified as Leveillula taurica. The host range was determined by inoculation of Leveillula taurica from tomato on nine species of plants belonging to four different plant families. All cultivars of tomato, eggplant, pepper and cucumber used in this study, showed disease symptoms on their leaf surfaces. Other plant species including potato, alfalfa, sunflower, clover and sainfoin did not get infected by the pathogen. The nucleotide divergence for the rDNA internal transcribed spacers (ITS) region between tomato mildew and 21 other Leveillula taurica isolates ranged from 0.00 to 0.031 %. The sequence of ITS region of Leveillula taurica from tomato was identical to that of eight isolates from different plant species.