Klebsiella jilinsis 2N3 promotes maize growth and induces resistance to northern corn leaf blight

Abstract The northern corn leaf blight (NCLB) is one of the most damaging diseases of maize and is caused by the hemibiotrophic ascomycete fungal pathogen Setosphaeria turcica. Previously, we reported that Klebsiella jilinsis 2N3 is a bacterium that can degrade sulfonylurea herbicides. Interestingly, we found that 2N3 can also promote maize growth and induce resistance to NCLB. 2N3 can grow in a nitrogen-free environment, dissolve inorganic phosphorus and potassium, and produce indoleacetic acid and a siderophore. To further evaluate its potential use in agriculture, the ability to promote maize growth and inhibit NCLB were determined by pot experiments. 2N3 significantly promoted the growth of maize seedlings and their chlorophyll content. After challenge inoculation for 14 days with S. turcica, the causal agent of NCLB, 2N3-treated maize plants showed a 67.44% decrease in the disease index. 2N3 enhanced the activities of catalase, phenylalanine ammonia lyase, peroxidase, superoxide dismutase, polyphenol oxidase, and chitinase in maize leaves. The mechanism of induction of resistance appeared to be primarily owing to the enhancement of the transcript levels of the marker genes of systemic acquired resistance (ZmPR1, ZmPR5, ZmOPR2, and ZmPAL) and the activation of the salicylic acid signaling pathway.