The forecast of canola (Brassica napus) production in 2017-2018 is almost double (350 ‎thousand ‎tons) its previous level (182 thousand tons) in Iran in 2016-2017. For this ‎reason Canola has been considered the most ‎important autumn oilseed in Iran. Blackleg is one ‎of the major limiting factors ‎on the development of this crop in the world and Iran. In the ‎northern parts of Iran, blackleg is the second most important disease, after the stem white rot ‎‎(Sclerotinia sclerotiorum). So far, L. ‎maculans has recorded in many parts of the world, like ‎Europe (Denmark, United Kingdom, ‎Germany, France, Czech Republic, Italy, Spain, Poland, ‎and Hungary), America (United States, ‎Mexico, Canada, Brazil and ‎Argentina), Oceania (Australia, New Zealand) and Asia (Iran, and India). A range of types of ‎disease have been ‎developed during the past years, ranging from non-aggressive ,Pathogenicity ‎Group 1 (PG1 strain) to aggressive (PG2, PG3, PGT, and ‎PG4), with increased growth of the ‎crop causing more prevalence of aggressive strains. It seems that there is a continuous struggle ‎between canola ‎and this microorganism, although the fungus ‎is ahead in this confrontation. Genetic variations in the populations of this organism and ‎technological ‎ advancements have allowed scientists to focus on the differentiation of the ‎populations of this ‎fungus on the pathogen genes (Avr) scale. In Iran, blackleg has ‎been ‎reported from 13 provinces and in a range of PG1,PG2,PG3,PGT and PG4, and it seems ‎that the development of rapeseed hybrids and climatic ‎conditions on the population diversity of ‎pathogens is more important than other ‎factors.‎