Adult-plant resistance of Panax notoginseng to nematodes and interspecific facilitation with pine trees

Root-knot nematode (RKN) is a soil-borne pathogen that severely damages Panax notoginseng . It has been recently shown that intercropping P. notoginseng in forests constitutes an innovative system that can promote P. notoginseng growth and suppress the spread of disease. However, there is little research on the interspecific interaction between pine trees and P. notoginseng . Here, two years of field experiments were designed to explore the effects of RKN infestation and P. notoginseng –pine tree intercropping on the growth and saponin synthesis of P. notoginseng . The results showed that RKN infestation could significantly reduce the root biomass, nutrient uptake and saponin accumulation of P. notoginseng seedlings. Interestingly, two-year-old P. notoginseng plants grew normally (specifically, root biomass, saponin synthesis, nutrient uptake and root morphology were normal) under nematode infection, while the incidence of RKN disease was decreased compared with that of seedlings before transplantation, indicating that P. notoginseng has adult-plant resistance (APR) to RKN disease. Furthermore, P. notoginseng –pine tree intercropping could significantly reduce the incidence of RKN disease and increase the biomass, nutrient uptake and saponin synthesis of P. notoginseng under mild infection, and root architecture may play a key role. Above all, P. notoginseng showed APR to RKN disease, and P. notoginseng –pine tree intercropping represents a type of interspecific facilitation that can promote the growth and quality of P. notoginseng .