Indigenous arbuscular mycorrhizal fungi enhance resistance of apple rootstock ‘M9T337’ to apple replant disease

Abstract

Apple replant disease is common in apple cultivation, leading to decay and necrosis of the root tip, growth retardation, and even death of the plant. Biological control, inducing activation of the plant's defense systems, is a promising alternative strategy for controlling the disease. In this study, we used the common rootstock ‘M9T337’ as the test material and harvested the plants at 60 and 120 days after transplantation. We investigated the physiological effects of inoculating the soil with indigenous arbuscular mycorrhizal fungi (AMF) to improve the resistance of the apple rootstock under replant conditions. The Glomus sp. and Paraglomus sp. acted as the major fungal species in QX and LZ. The results showed that inoculation of indigenous AMF increased the biomass of the plants and promoted root growth under replanting conditions. The antioxidant and defense-related enzyme activities in the plants were significantly raised, including the activities of the enzymes superoxide dismutase, peroxidase, catalase, ascorbate peroxidase, phenylalanine ammonia-lyase, and polyphenol oxidase. In the seedling root system, the H2O2 content and O2·− production were reduced, resulting in decreased lipid oxidation. Indigenous AMF treatment also induced the activity of chitinase and β-1,3-glucanase. This suggests that inoculation of indigenous AMF enhances the resistance of apple rootstock by regulating root reactive oxygen species levels and the antioxidant system under replanting conditions. This provides a theoretical basis for the prevention and treatment of apple replant disease.