Leptosphaeria species causing phoma stem canker on winter oilseed rape in the Czech Republic, occurrence and stem colonization

Phoma stem canker is an important disease of winter rape. It may be caused by two related pathogens, Leptosphaeria maculans and L. biglobosa. A survey of them was conducted from 2007-2012. Samples were analyzed by PCR. Of the 1159 Leptosphaeria spp. infected leaf spots, 49 and 19% were detected as L. maculans-and L. biglobosa-infected, respectively, in case of single species-infected samples, whereas 32% corresponded to co-infection by both species. Altogether 708 bases of oilseed rape plants were also tested. The proportion of plants in which L. biglobosa DNA was amplified was greater (62% in average) than that of plants with L. maculans DNA and 40% of tested plants were found to be co-infected by both L. maculans and L. biglobosa. These results suggest that L. maculans is predominant species in autumn, while L. biglobosa is more successful species than L. maculans in colonization of oilseed rape tissues in later growth stages of plant in conditions of the Czech Republic.