NONAGGRESSIVE STRAINS OF THE BLACKLEG FUNGUS, LEPTOSPHAERIA-MACULANS,ARE PRESENT IN AUSTRALIA AND CAN BE DISTINGUISHED FROM AGGRESSIVE STRAINS BY MOLECULAR ANALYSIS

Isolates of the pathogenic ascomycete Leptosphaeria maculans have been cultured from blackleg-affected oilseed rape (Brassica napus) stubble from Horsham, Victoria. These isolates are indistinguishable on the b asis of morphological characters, but can be classified as either aggr essive or non-aggressive by their ability to infect B. napus cultivars Midas and Westar. These aggressive and non-aggressive isolates of L. maculans can be distinguished by molecular techniques including electr ophoretic karyotyping, Southern analysis of the ribosomal RNA gene rep eat, Random Amplified Polymorphic DNA (RAPD) marker analysis, and pigm ent production. The presence of aggressive and non-aggressive strains of L. maculans in North America and Europe has been previously describ ed. This is the first report of non-aggressive L. maculans strains iso lated from B. napus in Australia.