PREVALENCE OF A HIGHLY VIRULENT STRAIN OF LEPTOSPHAERIA MACULANS (BLACKLEG) IN SEED SAMPLES OF RAPE AND TURNIP RAPE PRODUCED IN WESTERN CANADA IN 1976 AND 1977
A highly virulent strain of Leptosphaeria maculans (blackleg) was found in 17 (3.0%) of 570 Saskatchewan rapeseed samples, both pedigreed and commercial, produced in 1976 and 1977. All 17 originated in northeastern Saskatchewan. It was not detected in Alberta or Manitoba seed. Fourteen of the seventeen samples had less than 0.5% infected seeds; three had over 2.0%. A more geographically widespread weakly virulent strain occurred in 13% of the Saskatchewan samples. The significance of seed transmission of blackleg is discussed.