Piriformospora indica Enhances Resistance to Fusarium wilt in Strawberry by Increasing the Activity of Superoxide Dismutase, Peroxidase, and Catalase, While Reducing the Content of Malondialdehyde in the Roots

Strawberry Fusarium wilt, mainly caused by Fusarium oxysoporum f. sp. Fragariae (Fof), seriously threatens the yield and quality of strawberry. Piriformospora indica is an endophytic fungus that can colonise the roots of a wide range of plants, promoting plant growth and enhancing plant resistance. Against this background, the positive effects of P. indica on the growth of the daughter plants of ‘Benihoppe’ strawberry (Fragaria × ananassa Duch.) under Fof stress were investigated in this study. The study began by examining the inhibitory effect of P. indica on Fof growth through dual culture on agar plates. Subsequently, a symbiotic system between P. indica and strawberry plantlets was established, and the impact of P. indica on Fusarium wilt resistance and related physiological and biochemical indexes of the plantlets were evaluated. The results indicate that fungus colonization with P. indica significantly enhances the growth indices of strawberries, including plant height, petiole length, petiole diameter, and leaf area. Additionally, the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in the leaves of P. indica were increased, and the content of malondialdehyde (MDA) was decreased compared to those without colonization. Under the stress from Fof, the growth indexes of plant height, stem diameter, leaf area, petiole diameter, and root length of strawberry plants colonization with P. indica were significantly higher than those without colonization and the symptoms of wilting were relatively mild. The activities of SOD, POD, and CAT in roots and leaves of plants colonized with P. indica were significantly increased compared to those without colonization. Furthermore, the content of MDA in roots was decreased. These results suggested that P. indica could increase resistance to Fusarium wilt in strawberry by increasing the activity of antioxidant enzymes and reducing the content of MDA.