Determining Leptosphaeria species on Swedish oilseed rape and monitoring responses to Fusarium avenaceum and Fusarium graminearum in timothy populations

Abstract: Background Phoma stem canker or black leg disease is one of the most important disease affecting the oil seed rape worldwide. The disease is caused by the two pathogen species Leptosphaeria maculans and L. biglobosa. In this study genomic information of L. maculans and L. biglobosa was used to determine their presence in materials collected in the county of Sk ne, southern Sweden in 2020. The second part was carried out to understand if timothy is susceptible to pathogens that also cause disease on red clover. Sclerotinia trifoliorum, Fusarium avenaceum and F. graminearum were used to score their pathogenicity on timothy. Results The results showed that L. maculans and L. biglobosa co-existed in the oilseed rape stem master samples from the five fields analyzed. Pathogenicity observations showed that F. avenaceum and F. graminearum can cause symptoms similar to crown rot and root rot diseases seen on other crops whereas S. trifoliorum did not incite any disease. Conclusion This work should be seen as first preliminary data on potential disease problems in Sweden. Leptosphaeria maculans and L. biglobosa are now established in southern part of the country. These fungal pathogens constitute a potential future threat to Brassica crops particularly in light of climate change. Fusarium avenaceum and F. graminearum cause symptoms on timothy similar to root rot and crown rot on red clover and cereals. If the results could be further validated, they call for new efforts on resistance breeding.