A chromosome‐scale genome assembly reveals a highly dynamic effector repertoire of wheat powdery mildew

A chromosome‐scale genome assembly reveals a highly dynamic effector repertoire of wheat powdery mildew

- Blumeria graminis f. sp. tritici (B.g. tritici) is the causal agent of the wheat powdery mildew disease. The highly fragmented B.g. tritici genome available so far has prevented a systematic analysis of effector genes that are known to be involved in host adaptation. To study the diversity and evolution of effector genes we produced a chromosome-scale assembly of the B.g. tritici genome.
- The genome assembly and annotation was achieved by combining long-read sequencing with high-density genetic mapping, bacterial artificial chromosome fingerprinting and transcriptomics.
- We found that the 166.6 Mb B.g. tritici genome encodes 844 candidate effector genes, over 40% more than previously reported. Candidate effector genes have characteristic local genomic organization such as gene clustering and enrichment for recombination-active regions and certain transposable element families. A large group of 412 candidate effector genes shows high plasticity in terms of copy number variation in a global set of 36 isolates and of transcription levels.
- Our data suggest that copy number variation and transcriptional flexibility are the main drivers for adaptation in B.g. tritici. The high repeat content may play a role in providing a genomic environment that allows rapid evolution of effector genes with selection as the driving force.