Evaluating antofine's dual effects: Controlling Sclerospora graminicola infection while improving physiological performance and yield in foxtail millet

Sclerospora graminicola, a destructive oomycete pathogen, is the causal agent of downy mildew in foxtail millet (Setaria italica L.), a devastating disease that severely impacts crop productivity. Antofine, an alkaloid isolated from Cynanchum komarovii Al. Iljinski, exhibits significant inhibitory effects on S. graminicola. This study evaluated the effects of 2% antofine suspension (applied via seed coating) on physiological traits, nutritional quality, and yield in foxtail millet. The results revealed that 2% antofine treatment significantly enhanced plant growth parameters, including plant height, total root length, and root-shoot ratio during both seedling and jointing stages. The enzymatic analysis revealed that 2% antofine treatment induced peak activity of key defense-related enzymes at the elongation stage, with catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), and phenylalanine ammonia-lyase (PAL) showing significant increases of 11.06%, 34.70%, 345.67%, and 8.68%, respectively, compared to the control. Field trials demonstrated a 66.81% disease control efficacy, accompanied by a 22.01% yield increase (4245.58 kg/ha). Notably, antofine application significantly improved grain quality, elevating total sugar (8.26%), soluble sugar (67.32%), yellow pigment (12.04%), vitamin C (46.29%) and crude protein (30.64%) contents. These results collectively indicate that antofine functions as a multifunctional agent that not only suppresses S. graminicola infection but also activates plant defense mechanisms, enhances stress tolerance, and improves crop productivity and nutritional value. The study provides compelling evidence for antofine's dual role as both an effective biocontrol agent and a plant growth regulator in foxtail millet cultivation systems.