Abstract: To elucidate the physiological mechanisms by which silicon enhances oat resistance to stem rust, a pot experiment was conducted using the stem rust-susceptible oat cultivar “Bayou 1”. There were four treatments: no silicon application + no inoculation with stem rust fungus (CK), silicon application + no inoculation (+Si-P), no silicon application + inoculation (-Si+P), and silicon application + inoculation (+Si+P). We examined the effects of applying 1.5 mmol·L^-1 silicon on the disease progression, non-structural carbohydrate metabolism, and endogenous hormone levels in oat leaves. The results showed that: (1) Silicon application effectively delayed the progression of stem rust and significantly alleviated disease symptoms. (2) Stem rust infection initially increased and then decreased the levels of auxin, abscisic acid, and jasmonic acid in oat leaves, peaking on the third day after inoculation, while salicylic acid content continued to rise. Silicon application significantly increased the levels of auxin, abscisic acid, salicylic acid, and jasmonic acid in the leaves. (3) After inoculation with stem rust fungus, the sucrose and starch content in oat leaves first increased and then decreased, whereas glucose and fructose content exhibited a “decrease-increase-decrease” trend. Under silicon treatment, sucrose, glucose, and fructose content significantly increased, while starch content significantly decreased. (4) Following inoculation, the activities of sucrose synthase and  sucrose phosphate synthase showed a “increase-decrease-increase” pattern, while the activities of  acid invertase, and starch hydrolase in leaves all showed a “decrease-increase-decrease” pattern. Silicon application significantly enhanced the activities of sucrose synthase, sucrose phosphate synthase, and starch hydrolase but significantly reduced acid invertase activity. In conclusion, under stem rust infection, silicon application significantly improved the non-structural carbohydrate metabolism capacity and endogenous hormone synthesis in oat leaves, thereby effectively enhancing oat resistance to stem rust. Our findings provide a theoretical basis for novel disease control strategies against oat stem rust.

Key words: silicon, oat, stem rust, glucose metabolism, endogenous hormone