Screening of Brassica napus against blackleg caused by Leptosphaeria maculans: effects of inoculum concentration, subculturing of the pathogen, and time of disease screening

Abstract

The effects of inoculum concentration, subculturing of the pathogen, and time of disease screening on the development of blackleg disease caused by Leptosphaeria maculans were studied using the Brassica napus canola cultivars Quantum (resistant) and Profit (susceptible). Disease development was not affected by inoculum concentration in the range of 5 × 10⁵ - 4 × 10⁶ pycnidiospores/mL or subculturing of stock cultures of L. maculans up to 71 times on V8 juice rose Bengal agar. Disease development, however, showed seasonal variation in the greenhouse. While the disease severity values for the resistant cultivar Quantum increased during the summer, those for the susceptible cultivar Profit remained consistent throughout the year.

Keywords:

• Phoma lingam
• oilseed rape
• disease resistance