Heavy ion beam-induced variation in salt tolerance among <i>Leymus chinensis</i> genotypes during seed germination

Heavy ion beam irradiation (HIBI) is an efficient mutagenic tool characterized by high linear energy transfer and its capacity to induce heritable genetic variation. However, its application in perennial forage species remains limited, especially in terms of genotype-specific responses to radiation and salt tolerance. In this study, nine <i>Leymus chinensis</i> genotypes were irradiated with carbon ion beams at doses of 40, 50, and 80 Gy, with 0 Gy as the control. Germination responses were then evaluated under non-saline (distilled water) and saline (100 mmol·L^-1 NaCl) conditions to assess the effects of irradiation and genotype-specific salt tolerance. Both radiation dose and salt stress significantly affected early seedling development, showing pronounced genotype-dependent variation. Under 80 Gy combined with salt stress, emergence percentages of sensitive genotypes (<i>e.g</i>., G2, G4) dropped below 10%, whereas tolerant genotypes (<i>e.g</i>., G3, G9) exhibited a 19.3-65.1% increase under high-dose conditions. The half-lethal dose (LD₅₀), calculated based on emergence data, ranged from 29.6 Gy (G4) to over 80 Gy (G1), allowing classification into three salt tolerance levels: high, medium, and low. Principal component analysis (PCA) supported the trait-based classification and revealed synergistic variation patterns under combined stress conditions. These findings highlight the potential of HIBI to induce beneficial traits for salt tolerance in <i>L. chinensis</i>, providing a theoretical foundation for precision breeding and ecological restoration in saline grasslands.