# Deep population structure linked to host vernalization requirement in the barley net blotch fungal pathogen

## TL;DR

This study explores how the vernalization requirement of barley influences the population structure of the barley net blotch fungal pathogen Pyrenophora teres.

## Contribution

The study reveals a link between host vernalization requirements and population differentiation in the fungal pathogen Pyrenophora teres.

## Key findings

- Ptt and Ptm coexist in the same area in France, with Ptt predominating.
- Differences in vernalization requirements of barley varieties are associated with population differentiation within Ptt.
- One Ptt population cluster is found on spring barley, while another is found on winter barley.

## Abstract

Invasive fungal pathogens pose a substantial threat to widely cultivated crop species, owing to their capacity to adapt to new hosts and new environmental conditions. Gaining insights into the demographic history of these pathogens and unravelling the mechanisms driving coevolutionary processes are crucial for developing durably effective disease management programmes. Pyrenophora teres is a significant fungal pathogen of barley, consisting of two lineages, Ptt and Ptm, with global distributions and demographic histories reflecting barley domestication and spread. However, the factors influencing the population structure of P. teres remain poorly understood, despite the varietal and environmental heterogeneity of barley agrosystems. Here, we report on the population genomic structure of P. teres in France and globally. We used genotyping-by-sequencing to show that Ptt and Ptm can coexist in the same area in France, with Ptt predominating. Furthermore, we showed that differences in the vernalization requirement of barley varieties were associated with population differentiation within Ptt in France and at a global scale, with one population cluster found on spring barley and another population cluster found on winter barley. Our results demonstrate how cultivation conditions, possibly associated with genetic differences between host populations, can be associated with the maintenance of divergent invasive pathogen populations coexisting over large geographic areas. This study not only advances our understanding of the coevolutionary dynamics of the Pt-barley pathosystem but also prompts further research on the relative contributions of adaptation to the host versus adaptation to abiotic conditions in shaping Ptt populations.