Leptosphaeria maculans is the cause of "stem canker" (also termed "Blackleg") of canola. In Canada, the disease is responsible for more than 50% yield losses in some fields.

It has two mating types “+” and “-”. A “+” isolate can mate with a “-” isolate. To analyze genetic variation in this fungus, it is very useful to know which mating type an isolate belongs to. Conventional mating experiments can be used for determining mating type, but it is time consuming. Scientists at the University of Melbourne described the DNA sequences containing mating-type genes of L. maculans, and a mating-type can be determined with three primers by using PCR methods. (Cozijnsen and Howlett, 2003).

Isolates of L. maculans could be classed into 4 aggressive pathogenicity groups, PG2, PG3, PG4 and PGT based on reactions on canola cultivars Westar, Glacier and Quinta. To identify pathogenicity genes related to the PGs, we determined the mating-type of 29 isolates of L.maculans, which provide us a guide to choose isolates to carry out further mating experiments.