Diversity of aggressiveness of Sclerotinia sclerotiorum (Lib.) de Bary populations in oil plants fields of north and northeast of Iran

Sclerotinia sclerotiorum in which the infection is occurred by myceliogenic activity of sclerotia. In contrast, in the northern regions of the country, Sclerotinia stem rot is the most destructive disease on canola and the fungus germinates carpogenically to produce airborne ascospores. This study was conducted to compare aggressiveness of isolates of S. sclerotiorum populations in the above-mentioned areas in sunflower and canola fields. Variation in aggressiveness of isolates was assessed using mycelial plug inoculation technique and the measurement of lesion development was used to compare aggressiveness among isolates. Highly significant differences in aggressiveness were found among MCGs (P<0.001) from the north and northwest of Iran. The isolates belonging to MCGs such as MCG 56 which collected from different areas, showed significant differences of aggressiveness (P<0.001). But the isolates belonging to MCG17, MCG28, MCG42, MCG51 and MCG 64 which obtained from the same location in canola and sunflower fields, did not show significant differences of aggressiveness.