Ginsenoside Biosynthesis in Panax Ginseng with Red-Skin Disease Is Inhibited by Soil Characteristics

Red-skin disease (RSD) is a common soil-borne disease encountered during ginseng cultivation. We found that RSD was closely related to soil properties such as soil acidification and metal stress. The levels of active ingredients, especially ginsenoside, in RSD ginseng were reduced, thereby reducing its medicinal value. We investigated the inducing factors and pathological processes leading to RSD in ginseng and the soil properties responsible for the inhibition of ginsenoside biosynthesis. Healthy and RSD ginseng were compared for properties including the planting slope, soil moisture, soil pH, and metal content. Changes in metal absorption and ginsenoside synthesis at different pH were screened as inducers of RSD using ginseng cells. The activities of nitrate reductase, glutamate dehydrogenase, glutamate synthase, glutamine synthase, and squalene synthase were determined using enzyme-linked immunosorbent assay. The effect of nitrogen on ginsenoside synthesis was analyzed by culturing ginseng cells in a nitrogen-deficient environment. Field data showed that RSD ginseng grew at a slope of about 13 degrees and at a slower rate than healthy ginseng. RSD was caused when ginseng was grown in soils having higher water content and acidity. Acidic conditions inhibited the ginsenoside biosynthesis, whereas an increase in the pH of the medium could alleviate this inhibition. The overabsorption of aluminum ions in ginseng cells in acidic conditions was most significant. Aluminum stress not only inhibited the ginsenoside synthesis but also decreased the levels of nitrogen-containing compounds and enzyme activities related to nitrogen metabolism. Moreover, nitrogen concentration was positively correlated with ginsenoside content and squalene synthase activity. Our findings indicated that RSD was observed in ginseng when the planting slope was slow, there was water accumulation in the soil, and when the soil was acidic. Acidic conditions appeared to promote aluminum overabsorption in ginseng cells. The interference in aluminum stress-induced nitrogen uptake was found to inhibit ginsenoside synthesis in RSD. Our findings may contribute to a better understanding of the susceptibility factors and pathological processes in the RSD of ginseng.