Why to Study Concentration of Ascospores of Leptosphaeria maculans and L. biglobosa?

The fungal species Leptosphaeria maculans and L. biglobosa contribute to one of the most damaging diseases of oilseed rape, called stem canker of brassicas. The disease causes significant crop losses in Poland and worldwide. The primary source of infection of oilseed rape are ascospores of both species of the genus Leptosphaeria. These spores of the generative stage of the fungus are formed in pseudothecia fruiting bodies of the perfect stage of the fungus, located on crop residues from the previous growing season. Monitoring of the release of these spores allow to optimize the chemical protection and better combat the disease. In this study, concentration of ascospores in air was determined using Hirst-type volumetric samplers. The spores were trapped, stained, mounted on microscope slides and calculated, according to standard protocols. Seven-day operating traps were located in nine climatic regions in Poland and they operated in 2009/2010 and 2010/2011 within the framework of the System for Forecasting Disease Epidemics (SPEC, www.spec.edu.pl). In this paper exemplary results from Radostowo (Pomerania, central north Poland) are presented. The study shows that monitoring of ascospore concentration allows more efficient protection of oilseed rape against stem canker of brassicas, resulting in substantial increase of plant healthiness and the reduction of yield loss.