Dose-dependent γ-radiation effects on seed vigor and genomic mutation patterns in Shuidong mustard (Brassica juncea...

Shuidong mustard (Brassica juncea var. multiceps) is an important leafy vegetable in South China, yet its production is frequently constrained by seasonal drought stress during autumn sowing. Gamma (γ) radiation can induce genetic variation to potentially improve seed vigor and stress resilience. However, the dose-dependent effects of γ-radiation on seed physiological traits and genome-wide mutations in this crop remain unclear, limiting its effective application in mutation breeding.

Shuidong mustard seeds exhibited a biphasic response to ⁶⁰Co-γ irradiation (0-4000 Gy). Doses lower than 971 Gy (LD₅₀) induced manageable genomic stress, primarily generating single‑nucleotide substitutions, with only moderate effects on germination and root length. In contrast, high doses (≥ 2000 Gy) severely compromised viability, reducing fresh weight by 51.5% and disrupting genomic integrity-evident in elevated GC content (up to 41.44%) and a high frequency of large‑fragment deletions. Mutation analysis revealed dose‑stable hotspots, notably on chromosome AA_Chr09, and significant enrichment of mutations in genes related to DNA repair, ubiquitin‑mediated proteolysis, and central metabolism.

This study delineates the dose‑dependent physiological and genomic responses of Shuidong mustard to γ‑radiation. A dose of 971 Gy (LD₅₀) is proposed as a practical benchmark for mutation breeding, balancing the introduction of genetic diversity with acceptable physiological impact. Our results provide a genomic foundation for optimizing radiation‑based breeding strategies to enhance stress resilience, while also advancing the mechanistic understanding of DNA damage response and genome stability in plants.