Gamma-ray irradiation induces dose-dependent mutational signatures in Ganoderma resinaceum revealed by whole-genome...

Genetic variation is essential for fungal germplasm innovation, yet the genome-wide consequences of gamma-ray mutagenesis in Ganoderma spp. remain poorly resolved. Here, we evaluated gamma-ray-induced mutagenesis in the dikaryotic strain Ganoderma resinaceum G15 by irradiating protoplasts across a broad dose range, quantifying regeneration and plate-based growth phenotypes, and resequencing representative mutants. Under the screening criteria used in this study, 600-900 Gy provided a practical balance between lethality and mutant recovery and yielded stable mutants with increased mycelial growth after serial subculturing. Whole-genome resequencing identified single-base substitutions (SBSs) as the dominant variant class, with an average of 19 SBSs and 3 InDels per strain; SBS burden increased with irradiation dose, whereas InDels were less frequent and did not show a consistent dose-related pattern. The mutation spectrum showed an overall transition/transversion ratio of 1.18 and was enriched for C > T and A > G substitutions, indicating non-random base-change preferences among surviving irradiated mutants. Variants were unevenly distributed across the genome and were enriched in repeat-associated regions, a pattern consistent with negative selection against strongly deleterious lesions in essential coding regions. Functional annotation and enrichment analyses implicated candidate processes related to genome maintenance, stress-associated metabolism, transport, and cell wall remodeling, but these associations remain correlative and require functional validation. Collectively, these results provide a genome-level reference for interpreting gamma-ray-induced mutations in Ganoderma and a practical framework for selecting candidate irradiation ranges for strain improvement.