Leaf-Herbivore Induced Recruitment of Rhizosphere Microbiota: Enhancing Plant Defense against Insects and Soil-Borne Diseases in Agroforestry Systems

Agroforestry systems are characterized by high biodiversity and low pest and disease incidence. However, research on the simultaneous reduction of both diseases and pests within these systems is limited, necessitating further investigation the complex interactions among insects, plants, and microorganisms. In this study, we investigated the defensive strategies of Panax notoginseng against diseases and pests under varying levels of insect herbivory through a two-year field survey and greenhouse experiments. The shoots of P. notoginseng accumulated jasmonic acid (JA) and defensive substances in response to feeding by Spodoptera litura. Meanwhile, the secretion of secondary metabolites, particularly flavonoids, in the roots was suppressed, weakening the suppressing ability of flavonoids on rhizosphere microorganisms. This led to a significant enrichment of Mortierella, Bacillus, and Paenibacillus in the rhizosphere soil. These microorganisms not only enhanced the plant's resistance to insects but also exhibited antagonistic effects against soil-borne pathogens, thereby improving the survival of P. notoginseng. Our findings highlight the complex interactions among insects, plants, and microbes, and underscore the potential of harnessing beneficial microbes to bolster plant resilience in agroforestry systems, offering strategy for sustainable agriculture.