Improvement of Sphaeropsis Shoot Blight Disease Resistance by Applying the Ectomycorrhizal Fungus sp. Rl and Mycorrhizal Helper Bacterium HR10 to .

Ectomycorrhizal fungi (EMFs) form symbioses with plant roots to promote nutrient uptake by plants but it is controversial as to whether they induce disease resistance in plants. Here, we inoculated pine seedlings with , which was presymbiotic with the EMF sp. Rl, and the mycorrhizal helper bacterium (MHB) HR10, which promotes the formation of - sp. Rl mycorrhizae. The results showed that inoculation with sp. Rl, HR10, and the consortium significantly reduced pine shoot blight disease caused by . After inoculation with pathogenic fungi, callose deposition was significantly increased in needles of pine seedlings inoculated with sp. Rl, HR10, and the consortium, together with an increase in enzymatic and nonenzymatic systemic antioxidant activity as well as early priming for upregulated expression of and genes. Our findings suggest that ectomycorrhizal colonization enhances the resistance of pine seedlings to Sphaeropsis shoot blight by triggering a systemic defense response and that interactions between EMFs and MHBs are essential for mycorrhizal-induced disease resistance.