Driving factors for effective ingredients accumulation in Astragalus membranaceus of different growth years

To investigate the intrinsic relationship between the growth status, nutritional element content, soil physicochemical properties, and their effective ingredients in imitation wild Astragalus membranaceus under different growth years.

Imitation wild Astragalus plants of different growth years were collected, and their growth indexes such as fresh weight, dry weight, plant height, root length, root diameter, and the contents of total nitrogen, total phosphorus, total potassium, and effective ingredients (e.g., polysaccharides, total flavonoids, and trichothecene isoflavone glycosides) were measured. The pH value, relative moisture content, organic carbon, available phosphorus, available potassium, total nitrogen, and total phosphorus contents of the original soil and rhizosphere soil were also determined. The driving factors for the accumulation of effective ingredients in Astragalus under different growth years were explored by correlation analysis, principal component analysis, random forest model, and linear regression analysis.

The contents of polysaccharides, total flavonoids, and trichothecene isoflavone glycosides in Astragalus roots of different growth years all peaked in the fourth year of plant growth. Correlation analysis and random forest model revealed that the contents of these effective ingredients in Astragalus roots were positively correlated with the total potassium content in roots, available phosphorus, and available potassium content in the rhizosphere soil, while negatively correlated with the total nitrogen content in stems and the pH value of rhizosphere soil. Among them, total potassium content in roots was the determining factor for the accumulation of trichothecene isoflavone glycosides and total flavonoids in Astragalus roots, while the pH value of rhizosphere soil was the key driving factor for the accumulation of total sugar in Astragalus roots.

The most medicinally effective ingredients were accumulated in the four-year-old imitation wild Astragalus roots, which is of great practical significance in guiding medicinal farmers to plant and harvest Astragalus medicinal herbs. The total potassium content in Astragalus roots is the determining factor for the accumulation of trichothecene isoflavone glycosides and total flavonoids, highlighting the core role of potassium in the formation of Astragalus medicinal ingredients. Meanwhile, the influence of soil acidity and alkalinity on the accumulation of saccharides in Astragalus roots was also crucial, revealing the internal mechanism of the accumulation of effective ingredients in Astragalus and providing a scientific basis for the cultivation management and quality enhancement of imitation wild Astragalus.