S1-3: Race structure characterization of Leptosphaeria maculans causing oilseed rape blackleg disease in Tunisia from 2018 to 2020

Abstract: This study reports occurrence of the plant pathogenic fungi Leptosphaeria maculans and Leptosphaeria biglobosa in Tunisia and describes races of L. maculans present, assessed using a set of differential hosts carrying 9 major resistance genes (Rlm1, Rlm2, Rlm3, Rlm4, Rlm7, Rlm9, LepR1, LepR2 and LepR3). In total, 145 Tunisian isolates collected in three successive cropping seasons (2018, 2019 and 2020) were characterized. The experiments were done in controlled conditions in the Department of Crop Sciences, Georg-August-University of Göttingen (Germany). There were 11 L. maculans races identified. The presence of L. biglobosa was also confirmed and it represented 21 % of the isolates characterized. All L. maculans isolates were virulent against Rlm2, Rlm3 and Rlm9 resistance genes. However, Rlm7 and LepR1 resistance genes were still effective against the Tunisian L. maculans population. This work can be used to understand this new pathogen in Tunisia and to guide strategies for management of resistance against L. maculans in Tunisia.