Biological and Genomic Insights into Causing Needle Blight in .

Chinese pine, , is one of the most important garden plants in northern China, and the planting of this species is of great significance for the improvement of the ecological environment. In this study, different fungi were isolated and purified from diseased samples collected in Xi'an city, Shaanxi Province. Of these fungal isolates, only one (isolate AP-3) was pathogenic to the healthy host plant. The pathogenic isolate was identified as by morphological characteristics and and sequence analyses. The optimal growth conditions for this isolate were further analyzed as follows: Optimal temperature of 25 °C, pH of 11, soluble starch and sodium nitrate as the most preferred carbon and nitrogen sources, respectively. By combining Oxford Nanopore Technologies (ONT) long-read sequencing with Illumina short-read sequencing technologies, we obtained a 41.50 Mb genome assembly for AP-3, with 47.97% GC content and 3.04% repeats. This consisted of 14 contigs with an N50 of 4.64 Mb and a maximum length of 6.45 Mb. The BUSCO completeness of the genome assembly was 98.94% at the fungal level and 97.83% at the Ascomycota level. The genome assembly contained 13,408 protein-coding genes, including 421 carbohydrate-active enzymes (CAZys), 120 cytochrome P450 enzymes (CYPs), 3185 pathogen-host interaction (PHI) genes, and 694 candidate secreted proteins. To our knowledge, this is the first report of causing needle blight of . This study not only uncovered the pathogen responsible for needle blight of , but also provided a systematic analysis of its biological characteristics. These findings provide an important theoretical basis for disease control in and pave the way for further research into the fungal pathogenicity mechanisms and management strategies.