Role of Hydrolytic Enzymes of Rhizoflora in Biocontrol of Fungal Phytopathogens: An Overview

TLDR: This review focuses on the different aspects of various hydrolytic enzymes produced by rhizoflora and their role in sustainable biocontrol of phytopathogens.

Abstract: Microbial community in the rhizosphere produces a variety of hydrolytic enzymes that are responsible for the degradation of various components of fungal pathogens. The extracellular hydrolytic enzymes excreted by soil rhizobia degrade cell wall components of plant pathogenic microbes. The enzymes of these types are able to breakdown glycosidic linkages present in the polysaccharide of the cell wall of phytopathogens. In this regard, plant growth-promoting rhizobacteria (PGPR) are known to colonize rhizosphere and enhance plant growth through different mechanisms that include (i) plant growth promotion and (ii) biological control of plant disease. Plant growth promotion mechanisms include mineralization of insoluble substances, production of plant growth hormones, biological nitrogen fixation, and promotion of root growth. Biocontrol mechanism involves competition, antibiosis, parasitism, induction of systemic acquired resistance (SAR), induction of systemic resistance (ISR), soil suppressiveness, and production of various antifungal metabolites; hydrolytic enzymes such as chitinase, glucanase, protease, and cellulase; and antibiotics such as 2,4-diacetyl phloroglucinol (DAPG), amphisin, oomycin A, hydrogen cyanide, phenazine, pyoluteorin, pyrrolnitrin, cyclic lipopeptides, oligomycin A, zwittermicin A, kanosamine, and xanthobaccin. Production of hydrolytic enzymes by PGPR is an important mechanism directed against phytopathogens for sustainable plant disease management. These enzymes break down the cell wall of fungal pathogens causing cell death. This review focuses on the different aspects of various hydrolytic enzymes produced by rhizoflora and their role in sustainable biocontrol of phytopathogens.