Why is bacterial leaf streak absent from cereal crops in the EU while it is widespread on grass? Is cereal phytobiome playing a role?

Bacterial leaf streak, caused by Xanthomonas translucens pv. undulosa (Xtu), poses a significant threat to wheat crops. Absent in Europe, it is hypothesized that winter wheat, dominant on the continent, is less susceptible than spring wheat. Among the factors potentially influencing such resistance, the wheat-associated microbiota remains poorly known but could play a key role to explain Xtu pathogenicity. To assess whether microbial diversity specific to winter and spring wheat explains differences in resistance to Bacterial leaf streak, this project aims at conducting a comparative study of wheat varieties. It will focus on three key pathogen entry points: seeds, leaf and stomata and hydathodes, using two complementary approaches. First, metagenomic analysis will characterize microbial communities at these entry sites, examining variations by location, wheat variety and responses to infection. Second, the functional role of the microbiota in resistance will be investigated by in vitro antagonistic assays, analysis of microbial compounds via HPLC, and confocal microscopy to study microbial niches. Significantly, Xtu uses T4SS and T6SS to mediate interbacterial competition. Understanding their role in Xtu interactions with the wheat microbiota and their contribution to pathogenicity will shed light on wheat defense mechanisms. Identifying key microbiota species could help disrupt Xtu life cycle and improve disease prevention strategies.