Mutagenesis and transcriptomic analysis of a highly pathogenic <i>Alternaria alternata</i> DT-DYLC against <i>Chenopodium album</i> L

The development of bioherbicides is often limited by low herbicidal activity. To address this challenge, we enhanced the virulence of Alternaria alternata DT-DYLC, a biocontrol strain against Chenopodium album L., through combined UV and nitrite mutagenesis. Mutant strain J exhibited 2.4-fold higher pathogenicity in detached-leaf assays and 7.19% greater efficacy in pot trials compared to the wild-type strain. Transcriptome analysis during infection revealed 3060 differentially expressed genes, with 257 linked to metabolic processes. Notably, 87 co-expressed up-regulated genes were enriched in cell wall degradation enzymes, fungal toxin synthesis, and toxic compound transport, suggesting enhanced virulence mechanisms in mutant J. This study demonstrates that classical mutagenesis effectively improves fungal pathogenicity, while transcriptomic insights into virulence-related pathways provide a foundation for optimizing bioherbicide strains and understanding A. alternata's pathogenic biology.