The impact of wheat cultivar mixtures on virulence dynamics in <i>Zymoseptoria tritici</i> populations persists after interseason sexual reproduction

This study follows on from a previous showing that binary mixtures of wheat cultivars affect the evolution Zymoseptoria tritici populations within field epidemic beginning (t1) to end (t2) growing season. Here, we focused impact interseason sexual reproduction this evolution. We studied susceptible and resistant (carrying Stb16q, recently broken-down resistance gene) in proportions 0.25, 0.5 0.75, their pure stands. determined virulence status 1440 ascospore-derived strains collected each cultivar residue by phenotyping seedlings. Virulence frequencies population were lower than stands cultivar, especially residues, as at t2, revealing persisted until next season (t3). Surprisingly, after avirulence residues increased where proportion was higher. Our findings highlight two epidemiological processes: selection pathogen between t1 t2 driven asexual cross-contamination (previous study) crosses avirulent virulent t3 changes probabilities physical encounters (this study). Mixtures therefore appear be promising strategy for deployment qualitative resistances, not only limit intensity Septoria blotch epidemics, but also reduce erosion resistances managing pluriannual scale.