Drought priming at the seedling stage regulates secondary metabolism and nutritional components during the medicinal formation period in drought-tolerant and drought-sensitive Codonopsis pilosula cultivars

Climate change intensifies drought, which increasingly threatens the quality of medicinal plants. To explore the long-term effects of drought priming (DP) on medicinal plants, this study investigated two Codonopsis pilosula cultivars with distinct drought tolerance: drought-tolerant cultivar G1 and drought-sensitive cultivar W1. The plants were subjected to two treatments during the seedling period: drought priming (DP) and non-priming (NP). The results showed that during the seedling period, DP did not significantly increase antioxidant enzyme activity or the content of photosynthetic pigments but inhibited growth-related traits and yield-related characteristics. However, during the medicinal formation period, DP significantly enhanced the content of photosynthetic pigments (chlorophyll a, chlorophyll b, and carotenoids) by 18.2–20.0 %, improved antioxidant capacity (DPPH, ABTS, and FRAP activities increased by 18.6–49.0 %), and boosted the accumulation of secondary metabolites (total polyphenols, total flavonoids, and total alkaloids increased by 19.6–21.2 %, 15.7–17.1 %, and 72.2–74.5 %, respectively). Additionally, DP significantly improved nutritional quality by increasing crude protein (16.8–33.8 %), crude fat (78.9–85.8 %), and total dietary fiber (37.2–63.3 %). The effects of DP exhibited clear genotype dependency. Under DP conditions, the drought-tolerant cultivar G1 contained 60.1 % more atractylenolide III than the drought-sensitive W1, but DP treatment narrowed the genotypic gap by substantially enhancing atractylenolide III accumulation in W1. Meanwhile, DP significantly increased the content of syringin, a characteristic component of the W1 cultivar. In summary, DP induces a stress memory effect in C. pilosula, significantly enhancing antioxidant capacity, the content of key bioactive components, and nutritional quality during the medicinal formation period. Furthermore, DP mitigates inherent differences between cultivars by improving the quality of the drought-sensitive cultivar while reinforcing the advantages of the drought-tolerant cultivar. This study unveils the concept of “trans-phase stress memory” in medicinal plants, demonstrating that early drought exposure primes long-term biochemical reprogramming and provide critical theoretical support for the application of green cultivation techniques, such as stress priming, to achieve “quality improvement and efficiency enhancement” in medicinal plants.