Equal Distribution of Mating Type Alleles and the Presence of Strobilurin Resistance in Algerian Zymoseptoria tritici Field Populations.

Abstract

Zymoseptoria tritici, the causal agent of septoria tritici blotch, is an important wheat pathogen responsible for high yield losses worldwide. The assessment of the distribution of both mating type idiomorphs was studied in several wheat-growing areas in North Algeria. Both mating types occurred at all spatial scales tested and showed an equal frequency distribution at the country level, with 53% for Mat1-1 and 47% for Mat1-2. At finer scales, co-occurrence of both mating types was found in 38% of leaves analyzed and 44% of the studied lesions. Additionally, efficacy reduction of strobilurin applications prompted us to study strobilurin resistance conferred by the G143A substitution in the mitochondrial cytochrome b gene, which was found for the first time in six strains. The results suggest that the Algerian Z. tritici population undergoes frequent sexual reproduction mirrored by co-occurrence of both mating types, which likely will rapidly increase the fraction of strobilurin-resistant isolates in the Algerian population, as has been shown in all other regions where strobilurin resistance surfaced.