P-304 - The role of transposable elements in the evolution of Blumeria hordei

We aim to quantify the neutral and selective processes driving genome evolution in the obligate

crop pathogen Blumeria hordei (Bh), a filamentous fungus and the causative agent of powdery

mildew on barley. Bh carries a high load of transposable elements (TEs), making up around 75% of its genome, possibly due to a recent multiplication of TEs in the genome. Although most TEs are likely to have neutral or negative effects on Bh fitness, it is speculated that their presence may also

confer selective advantages in the co-evolution of Bh with its cereal host, barley.

To assess population genetic processes, we have collected 50 Bh strains in 2023 and 2024, a

sample of the current population in Germany. The genomes of all strains were sequenced using

short-read DNA technology (Illumina). Furthermore, the genomes of a diverse subset were

sequenced with long-read DNA technology (Oxford Nanopore). Using the long-read sequences, we create a Bh pan-genome with a detailed annotation of TEs. This resource provides a near complete set of TE insertion sites, which will help to assess the presence and absence of TEs in the wider population. Using SNPs in coding regions, we first infer the past demographic history and population structure. We then search for positive selective events (selective sweeps) in coding regions and finally we infer the distribution of fitness effects at TEs based on their presence/absence polymorphism.