Transcriptome sequence resource for the hazelnut powdery mildew pathogen Erysiphe corylacearum

Erysiphe corylacearum is the main causal agent of hazelnut powdery mildew, causing substantial damage in the Black Sea region of Türkiye. Despite its economic importance, molecular resources for this obligate biotrophic pathogen remain severely limited. This study presents the first comprehensive transcriptomic dataset for E. corylacearum obtained through Illumina sequencing of mRNA from naturally infected hazelnut leaves. Using targeted epidermal peeling to enrich fungal material while minimizing host contamination, over 66 million high-quality paired-end reads were generated. De novo Trinity-based assembly yielded an initial set of 135,404 unigenes for annotation, and the final NCBI-cleaned TSA submission contains 100,824 transcript sequences. Functional annotation assigned database matches to 71% of the initial unigene set, including sequences related to pathogenicity, sexual compatibility, and reproduction. The dataset also includes over 29,000 high-confidence intra-sample sequence variants from this single metatranscriptomic sample providing a candidate resource for future marker development, diagnostic assays, and comparative analyses pending validation across additional isolates. This transcriptomic resource will facilitate investigations into pathogen biology, host-pathogen interactions, and improved disease management strategies.