Standing genetic variation buffers field populations of Zymoseptoria tritici against seasonal and fungicide selection

Zymoseptoria tritici, a wheat pathogen, exhibits significant genetic variation that aids in rapid adaptation and undermines disease control methods. However, the role of seasonal demographic turnover and fungicide selection in within-season genomic changes at the field level remains unclear. To clarify these factors, researchers conducted a comprehensive analysis of whole-genome sequences from five wheat fields, comparing untreated and fungicide-treated populations.

The findings revealed that field populations were locally distinct yet connected to the wider European gene pool. Within-season demographic turnover consistently shifted allele frequency spectra towards common alleles, while maintaining similar nucleotide diversity and adaptive potential. Seasonal demographic turnover was the primary driver of short-term genomic changes, accounting for the majority of alterations.

Fungicide effects were minimal, field-specific, and mainly impacted pre-existing resistance alleles and existing genetic variation. The study highlights the importance of pathogen population biology in determining disease-control durability and underscores the significance of population-informed genomic surveillance.