PGPR‐mediated induction of systemic resistance and physiochemical alterations in plants against the pathogens: Current perspectives

Abstract

Plant growth‐promoting rhizobacteria (PGPR) are diverse groups of plant‐associated microorganisms, which can reduce the severity or incidence of disease during antagonism among bacteria and soil‐borne pathogens, as well as by influencing a systemic resistance to elicit defense response in host plants. An amalgamation of various strains of PGPR has improved the efficacy by enhancing the systemic resistance opposed to various pathogens affecting the crop. Many PGPR used with seed treatment causes structural improvement of the cell wall and physiological/biochemical changes leading to the synthesis of proteins, peptides, and chemicals occupied in plant defense mechanisms. The major determinants of PGPR‐mediated induced systemic resistance (ISR) are lipopolysaccharides, lipopeptides, siderophores, pyocyanin, antibiotics 2,4‐diacetylphoroglucinol, the volatile 2,3‐butanediol, N‐alkylated benzylamine, and iron‐regulated compounds. Many PGPR inoculants have been commercialized and these inoculants consequently aid in the improvement of crop growth yield and provide effective reinforcement to the crop from disease, whereas other inoculants are used as biofertilizers for native as well as crops growing at diverse extreme habitat and exhibit multifunctional plant growth‐promoting attributes. A number of applications of PGPR formulation are needed to maintain the resistance levels in crop plants. Several microarray‐based studies have been done to identify the genes, which are associated with PGPR‐induced systemic resistance. Identification of these genes associated with ISR‐mediating disease suppression and biochemical changes in the crop plant is one of the essential steps in understanding the disease resistance mechanisms in crops. Therefore, in this review, we discuss the PGPR‐mediated innovative methods, focusing on the mode of action of compounds authorized that may be significant in the development contributing to enhance plant growth, disease resistance, and serve as an efficient bioinoculants for sustainable agriculture. The review also highlights current research progress in this field with a special emphasis on challenges, limitations, and their environmental and economic advantages.

Rhizosphere Bacteria in Plant Growth Promotion, Biocontrol, and Bioremediation of Contaminated Sites: A Comprehensive Review of Effects and Mechanisms

“…The efficiency of applied inoculants deteriorated in the presence of many other microorganisms under field conditions. Thus, target strains should be chosen based on their performance under field conditions, and they should be applied to various crops and grown in a variety of soil types [ 385 ]. The selected bioinoculant in a biofertilizer could be less effective at replacing native ineffective strains, less compatible with a crop, and less capable of colonizing host plant roots and thriving in soil [ 367 ].…”

“…Regulatory constraints include difficulties in registering biofertilizer products and filing patents due to frequently changing and inconsistent regulations among regions and countries. The entire regulatory process of developing a potential biofertilizer, from registration to commercialization, is lengthy, potentially taking several years, and quite complex [ 385 ]. Financial constraints are a serious hindrance to large-scale biofertilizer production.…”

Endophytic Nanotechnology: An Approach to Study Scope and Potential Applications

“…Therefore, these unique characteristics make them an ideal alternative for drug delivery. The drug-carrying capacity, stability and delivery systems of organic NPs, either in the form of entrapped drugs or adsorbed drugs system determines their field applications and their effectiveness (Ealias and Saravanakumar, 2017;Meena et al, 2020a;Meena et al, 2020b). Organic NPs are also most widely used in the biomedical field (Yang et al, 2019).…”

Recent Advances in PGPR and Molecular Mechanisms Involved in Drought Stress Tolerance

“…There are many earlier reported studies suggesting about the increased GA level after inoculating with rhizobacteria e.g. using consortium of Acinetobacter implicates their benefits under several abiotic stress (69).…”