Virulence spectrum of Moroccan Zymoseptoria tritici isolates and efficacy of Septoria tritici blotch resistance genes

Septoria tritici blotch (STB) caused by Zymoseptoria tritici is a major biotic stress in temperate wheat-growing regions of Morocco with yield losses reaching up to 40% under favourable conditions. Owing to the development of fungicide resistance, the use of resistant cultivars seems to be the best option for managing this disease. Therefore, knowledge of the pathogen population structure is indispensable for deploying an efficient and effective resistance breeding approach to combat STB. In this study, the response of 33 bread wheat genotypes (representing 16 resistance genes and QTL) was evaluated against 21 Z. tritici isolates under controlled conditions. Among 693 genotype-isolate interactions, 163 isolate-specific resistances (24%) were observed by comparing the means of disease severity data using LSD0.01 and LSD0.05. In addition to resistant cultivar Murga (G25), two cultivars, Cs synthetic (G4) and KK 4500 (G9), exhibited resistance response to almost all isolates with mean disease severity of 4% and 14–15 isolate-specific resistances. This suggests that these genotypes can be utilized in STB resistance breeding programs for Morocco and durable resistance can be achieved by pyramiding identified R genes against Moroccan Z. tritici isolates.