Dose-effect analysis of 60Co-γ radiation on Astragalus membranaceus across life cycle and creation of high-flavonoid/super-biomass germplasm

This study aimed to systematically investigate the dose-dependent effects of 60 Co-γ radiation on the entire growth cycle of Astragalus membranaceus , using a dose gradient ranging from 50 to 400 Gy. The specific objectives were to evaluate its impacts on seed germination, seedling physiology, agronomic traits of one-year-old plants, and the accumulation of medicinal components. A radiation dose gradient of 50–400 Gy was applied to Astragalus membranaceus seeds. Assessments included seed germination and seedling emergence rates, physiological and biochemical markers (e.g., antioxidant enzyme activities and secondary metabolites), agronomic traits, and medicinal compound accumulation. The median lethal dose (LD 50 ) was calculated, and a multi-trait weighted index (I) was used to screen superior germplasm lines. Low-dose radiation (50–100 Gy) significantly improved seed germination and emergence rates, while high doses (≥200 Gy) were inhibitory, with an LD 50 of 201.95 Gy. At 50 Gy, antioxidant defense mechanisms were activated, indicated by increased CAT and APX activities, and flavonoid content rose by 48.2 %. Doses≥300 Gy caused severe damage, including a 57.8 % reduction in thylakoid density. In one-year-old plants, 50 Gy synergistically improved biomass and active compound content. Doses of 100–300 Gy induced transgressive segregation: one line (300 Gy-2) showed a root dry weight 4.63 times that of the control. Using a multi-trait index, seven superior lines were selected. Line 100 Gy-8 exhibited a 1.54-fold increase in total flavonoids (93.03 mg/g), while line 400 Gy-12 showed a threefold enhancement. The results indicate that 50 Gy is an optimal dose for simultaneously improving yield and quality in Astragalus membranaceus , whereas the 100–300 Gy range serves as a promising mutagenic window for generating high-flavonoid or high-biomass variants. This study provides theoretical support and core germplasm resources for targeted breeding strategies.