Dual Role of Bacillus velezensis EM-A8 in Maize: Biocontrol of Exserohilum Turcicum and Enhancement of Plant Growth

Abstract

Northern corn leaf blight (NCLB), caused by Exserohilum turcicum, is a major foliar diseaseof maize worldwide. To develop sustainable alternatives that reduce chemical products,we evaluated Bacillus velezensis EM-A8 (GenBank accession number OL704805) as a bio￾control agent under greenhouse and field conditions. The aims of this study were asfollows: (i) characterize phytohormone production in two formulations containing theBCA; (ii) assess the influence of the BCA on plant biomass and yield; (iii) compare theefficacy of both formulations in controlling NCLB under field conditions; and (iv) deter￾mine whether the treatments affected salicylic acid and phenolic compound levels in maizetissues. The strain synthesized a broad spectrum of phytohormones, including salicylicacid, indoleacetic acid, indolebutyric acid, jasmonic acid, abscisic acid and gibberellic acid,as well as cytokinins such as kinetin, zeatin, and 6-benzylaminopurine. Foliar applicationincreased maize dry biomass by 30%. In field trials, both formulations effectively sup￾pressed NCLB, reducing the number of symptomatic leaves by 25–50% compared withcontrols. Furthermore, treated plants exhibited yield increases exceeding 1000 kg/ha. Thesefindings demonstrate that B. velezensis EM-A8 provides effective biocontrol of E. turcicumwhile simultaneously enhancing maize growth and yield under field conditions. Futurework should aim to scale up the use of B. velezensis EM-A8 in integrated pest manage￾ment programs and evaluate its long-term impact on soil microbiota, plant health, andyield sustainability.