produce variable metabolites such as antibiotics, siderophores, salicylic acid (SA), lipopolysaccharides (LPS) and hydrolytic enzymes to suppress pathogen either directly or through enhancing the plant defense mechanisms. are recognized as valuable biocontrol agents against diverse phytopathogens through induction of systemic resistance as well as improve efficacy through consistency under field conditions. The PGPR bioformulation suppressed the early blight disease in tomato by elevating the activity of antioxidant enzymes such as PAL, PO, PPO, chitinase, ОІ-1,3-glucanase, superoxide dismutase, catalase, lipoxygenase, and phenolics. Several studies show the ability of beneficial microbes to stimulate variety of defense reactions in host plants, in response to pathogen infection, particularly, activity of antioxidant defense enzymes. Therefore, the pathogen can be trapped in dead cells and seems to be restricted to the initial infection site. The biotic agents elicit responses around the infected plant cells which cause the cell death through incompatible interactions. ISR in plants is induced by a number of biotic and abiotic agents. The phenolic compounds and specific flavonoids induce resistance in host plants after challenge inoculation of pathogens. PAL initiates the phenylpropanoid pathway, resulting in the biosynthesis of phytoalexins and/or phenolic compounds. The PO, and PPO enzymes are responsible for the production of phenolic compounds which contribute to the reinforcement of cell barriers. The activities of various antioxidant enzymes help the plants to mitigate the reactive oxygen species (ROS) level which is source of oxidative stress during pathogen infection. The antioxidant enzymes peroxidase (PO), phenylalanine ammonia lyase (PAL) and polyphenol oxidase (PPO) might be elicitors of ISR as their activity in plant has been highly correlated with disease suppression. ISR is an effective defensive mechanism which is manifested as a result of certain physiological changes in the plant, such as modification in cell wall structure and de novo synthesis of antimicrobial compounds like pathogenesisвЂђrelated (PR) proteins and phytoalexins, that prevent the dispersion of pathogens. Enhanced plant immunity referred as вЂњinduced systemic resistanceвЂќ (ISR) is one of the important mechanism used by various PGPR to secure the plant against extensive range of fungal, bacterial and viral pathogens. They suppress phytopathogens by utilizing various mechanisms in their habitation. Plant growth promoting rhizobacteria (PGPR) are being widely used as an alternative to chemical fungicides and fertilizers due to their eco- friendly nature. oryzae induced oxidative damage and suppressing blast disease incidence. enhanced the antioxidant defense activities in infected rice, thus alleviating P. The results showed that treatment with Bacillus spp. Furthermore, the antagonistic Bacillus spp significantly colonized the rice plants (2.0E+00вЂ“9.1E+08) and secreted multiple biocontrol determinants like protease (1.1вЂ“5.5 U/mg of soil or U/mL of hydroponic solution), glucanase, (1.0вЂ“1.3 U/mg of soil or U/mL of hydroponic solution), siderophores (6.5вЂ“42.8 Ојg/mL or mg) in the rhizosphere of different rice varieties. significantly induced antioxidant defense enzymes i-e superoxide dismutase (1.7вЂ“1.9-fold), peroxidase (3.5вЂ“4.1-fold), polyphenol oxidase (3.0вЂ“3.8-fold), phenylalanine ammonia-lyase (3.9вЂ“4.4-fold), in rice leaves and roots under hydroponic and soil conditions respectively. KFP-5, KFP-7, KFP-17 was assessed to induce antioxidant enzymes against Pyricularia oryzae infection in rice. In the present study, potential of Bacillus spp. Rhizobacteria elicit ISR by inducing different pathways in plants through production of various metabolites. Induced systemic resistance (ISR) is an important defensive strategy manifested by plants against numerous pathogens especially infecting at aerial parts. Plant growth promoting rhizobacteria (PGPR) are found to control the plant diseases by adopting various mechanisms.

Microbial biocontrol agents ppt