Enterobacter cloacae Induces SA-Dependent Systemic Acquired Resistance of Zea mays Against Fusarium oxysporum

Plant Growth Promoting Bacteria have proven themselves in agricultural applications not only as biofertilizers but also as biocontrol agents against different phytopathogens. In this study, we focused on investigating the ability of Enterobacter cloacae to induce the immune response of Zea mays against Fusarium oxysporum infection. The bacterium was transformed with a plasmid to express Green Fluorescence Protein and used in a greenhouse experiment in combination with Fusarium infection in different treatments. E. cloacae successfully colonized the root, resulting in enhanced physical growth with great investment in leaf area, photosynthetic pigment production, and reduced anthocyanin content. E. cloacae left a considerable resistance to root rot caused by Fusarium, as the disease severity was reduced from 74.2% (in the case of Fusarium infection alone) to about 35.8% (in the case of E. cloacae addition 14 days before fungal infection). The amount of salicylic acid (SA) was markedly elevated, and Pathogen-Related Protein showed up to an eightfold increase in the expression level. From these results, we suppose that E. cloacae induces SA-dependent systemic acquired resistance, which allows pre-colonized plants to resist Fusarium infection.