Abstract:

To address the inconsistency in the quality of Astragalus caused by ambiguous cultivar selection and indeterminate harvesting periods in Northern China, this study aimes to identify suitable cultivars and determine the optimal harvest time. Using A. membranaceus var. mongholicus (AM) and A. membranaceus (AG) as experimental materials, we systematically evaluated their growth parameters, including root length, root diameter, fresh root weight, and dry root weight, as well as the contents of key medicinal compounds (calycosin-7-glucoside, ononin, calycosin, and crude polysaccharides) across different cultivation years (1 to 3 years). The monthly dynamics of these bioactive components in both Astragalus species were monitored. Principal component analysis (PCA) was subsequently employed to comprehensively assess the quality of Astragalus at different growth stages. The results indicated: (1) Both growth parameters and medicinal compound contents in the two Astragalus species increased significantly with cultivation years. The 3-year-old AM exhibited marked growth advantages, with its dry root weight increasing by 250.37% compared to 2-year-old plants, and its calycosin content showing a significant increase of 1197.56% to 1533.58% relative to 1- and 2-year-old plants. The dry root weight of 3-year-old AG increased significantly by 193.78% compared to 2-year-old plants, with its calycosin content rising by 516.33% to 522.50% compared to 1- and 2-year-old plants. (2) The root length, fresh root weight, dry root weight, and contents of calycosin-7-glucoside, ononin, and calycosin in 3-year-old AM were all significantly higher than those in AG. (3) Monthly dynamics revealed that the bioactive compounds (calycosin-7-glucoside, ononin, calycosin) in AM followed an “N”-shaped change pattern, peaking at 29 months. In AG, calycosin-7-glucoside and crude polysaccharides exhibited an “M”-shaped change pattern, with peaks occurring at 28-29 months. (4) PCA results demonstrated clear separation between 3-year-old and 1-year-old Astragalus (cumulative contribution rate: 80.340%), with 3-year-old AM showing the highest yield and quality. In conclusion, A. membranaceus var. mongholicus (AM) demonstrated superior growth and quality performance compared to A. membranaceus (AG) in northern regions, with the optimal harvest time identified as October of the third year (29 months of age). This study provides a scientific basis for high-quality and high-yield cultivation of Astragalus in Northern China. Future research could further optimize cultivation practices by incorporating multi-location trials and molecular mechanism analysis.

Key words: growth duration, Astragalus membranaceus var. mongholicus, Astragalus membranaceus, harvesting period, growth increment, medicinal components, principal component analysis