Objective This study aimed to clarify the control effect of Bacillus subtilis B15 against northern maize leaf blight in fresh-eating maize and its regulatory mechanisms on plant physiological characteristics, yield, and quality, thereby providing a theoretical basis and technical support for the green prevention and control of northern leaf blight and the high-quality, high-yield production of fresh-eating maize.

Method Using the fresh-eating maize variety 'Shannong Tiannuo 3' as test material, different concentrations of B. subtilis B15 bacterial suspension were applied as foliar sprays, with clear water and a chemical fungicide serving as controls. The treatments were: T0 (water control), T1 (chemical control), T2 (bacterial powder∶water = 1∶500), T3 (bacterial powder∶water = 1∶250), and T4 (bacterial powder∶water = 1∶125). The control effect on northern leaf blight was assessed. Concurrently, soil enzyme activities, key plant physiological indexes, as well as core yield and quality indexes were analyzed.

Result The control effect of B. subtilis B15 against northern leaf blight exhibited a significant dose-dependent response. At 14 days after treatment, the control effects for T2, T3, and T4 reached 87.74%, 89.82%, and 93.45%, respectively. The persistence of the T4 treatment was notably superior to that of the chemical control. Physiological indexes revealed that all B. subtilis treatments significantly enhanced soil enzyme activities, improved root activity, increased antioxidant capacity, and reduced lipid peroxidation damage in plants, with effects intensifying at higher concentrations. Regarding yield and quality, the T4 treatment achieved the highest yield of 19.82 t/hm², representing a significant increase of 39.28 with the blank control. Furthermore, the T4 treatment significantly increased the contents of total sugar, reducing sugar, and crude protein in kernels by 29.93%, 55.09% and 28.92%, respectively, while significantly decreasing starch content by 10.37%. The T2 and T3 treatments also showed significant superiority over the blank control across all measured indicators.

Conclusion B. subtilis B15 can effectively control northern leaf blight in fresh-eating maize by enhancing soil microecological functions and activating the plant's intrinsic stress-resistant physiological system, simultaneously leading to increased yield and improved quality. The high-concentration treatment (bacterial powder∶water = 1∶125) demonstrated the optimal overall effect and can be proposed as a viable technical solution to replace chemical pesticides, facilitating the green, high-yield, and high-quality production of fresh-eating maize.