Seed Biopriming with Microbial Inoculant Triggers Local and Systemic Defense Responses against Causing Banded Leaf and Sheath Blight in Maize ( L.).

Plant growth promoting rhizobacteria strain MF-30 isolated from maize rhizosphere was characterized for several plant growth stimulating attributes. The strain MF-30 was also evaluated for antifungal properties against causing banded leaf and sheath blight in maize ( L.) under in vitro conditions and was found to have higher mycelial growth suppression in the culture suspension (67.41%) followed by volatile organic compounds (62.66%) and crude extract (51.20%) in a dual plate assay. The endophytic and epiphytic colonization ability was tested using Green Fluorescent Protein (GFP)-tagging. Visualization through confocal scanning laser microscope clearly indicated that strain MF-30 colonizes the root and foliar parts of the plants. Further, the effects of seed bio-priming with MF-30 was evaluated in the induction and bioaccumulation of defense-related biomolecules, enzymes, natural antioxidants, and other changes in maize under pot trial. This not only provided protection from but also ensured growth promotion under pathogenic stress conditions in maize. The maximum concentration of hydrogen peroxide (HO) was reported in the root and shoot of the plants treated with alone (8.47 and 17.50 mmol mg protein, respectively) compared to bioagent, MF-30 bio-primed plants (3.49 and 7.50 mmol mg protein, respectively). Effects on total soluble sugar content, total protein, and total proline were also found to enhanced significantly due to inoculation of MF-30. The activities of anti-oxidative defense enzymes phenylalanine ammonia lyase (PAL), ascorbate peroxidase, peroxidase, superoxide dismutase, and catalase increased significantly in the plants bio-primed with MF-30 and subsequent foliar spray of culture suspension of MF-30 compared to pathogen alone inoculated plants. qRT-PCR analysis revealed that seed bio-priming and foliar application of MF-30 significantly increased the expression of PR-1 and PR-10 genes with the simultaneous decrease in the disease severity and lesion length in the maize plants under pathogenic stress conditions. A significant enhancement of shoot and root biomass was recorded in MF-30 bio-primed plants as compared to untreated control ( < 0.05). Significant increase in plant growth and antioxidant content, as well as decreased disease severity in the MF-30 bio-primed plants, suggested the possibility of an eco-friendly and economical means of achieving antioxidants-rich, healthier maize plants.