Ganoderma lucidum Polysaccharide Seed Dressing Induces Systemic Resistance Against Fusarium Head Blight and Sharp Eyespot in Wheat

Ganoderma lucidum polysaccharide (GLP) exhibits prominent antibacterial and antioxidant activities. This study evaluated the effects of GLP seed soaking at two concentrations (4 g/100 kg, GLP4; 8 g/100 kg, GLP8) on wheat growth promotion and induced resistance against wheat sharp eyespot caused by Rhizoctonia solani and Fusarium head blight (FHB) mainly caused by Fusarium graminearum. Physiological and agronomic analyses showed that GLP treatment increased the germination rate of all tested wheat cultivars (moderately resistant: Xiaoyan 22, Sumai 3; moderately susceptible: Mingxian 169, Xinong 873) by over 2%. Moderately susceptible and resistant cultivars presented average plant height increases of 0.5 cm and 2 cm, respectively, with most cultivars showing a height increase of approximately 3 cm. GLP significantly elevated leaf chlorophyll content by over 5% and differentially regulated malondialdehyde (MDA) levels: MDA decreased by 34–68% in Sumai 3 and Mingxian 169 but increased by 11–23% in Xiaoyan 22. Pot assays verified that GLP yielded over 10% control efficacy against both diseases. Overall, GLP seed soaking effectively promotes wheat growth, activates defense responses, and enhances host resistance to R. solani and F. graminearum infections.