Telomere-to-Telomere Genomes Reveal that Multiscale Evolution Shapes the Largest Metabolic Arsenal of Diaporthe Fungi.

The fungal genus Diaporthe poses a significant threat to global food security by causing devastating crop diseases, including soybean seed decay and stem blight caused by D. longicolla. However, the molecular basis of its pathogenicity and the evolutionary mechanisms underlying its virulence remain poorly understood. Here, we present complete telomere-to-telomere genome assemblies of four Diaporthe species, revealing extensive chromosomal rearrangements correlating with phylogenetic divergence. Comparative analyses of 34 Diaporthe genomes identified secondary metabolism genes as the most variable fraction. Comprehensive genome exploration across fungi has revealed that Diaporthe harbors the largest repertoire of secondary metabolite biosynthetic gene clusters (SMBGCs) reported to date. We demonstrate that frequent chromosomal rearrangements and rapid intra-cluster gene variation are key drivers of SMBGC diversification, thereby accelerating the evolution of these gene clusters. Interestingly, we identified horizontal gene transfer events that further expanded the metabolic potential of these clusters. Functional characterization of the five rapidly evolving SMBGCs identified demonstrated their direct role in mediating pathogenicity, underscoring the biological significance of their rapid diversification. Collectively, this study establishes chromosomal plasticity as a crucial mechanism for ecological adaptation and secondary metabolite arsenal expansion in plant pathogens, providing new insights into the evolution of fungal virulence.