Biotechnological approaches to develop bacterial chitinases as a bioshield against fungal diseases of plants

Abstract

Fungal diseases of plants continue to contribute to heavy crop losses in spite of the best control efforts of plant pathologists. Breeding for disease-resistant varieties and the application of synthetic chemical fungicides are the most widely accepted approaches in plant disease management. An alternative approach to avoid the undesired effects of chemical control could be biological control using antifungal bacteria that exhibit a direct action against fungal pathogens. Several biocontrol agents, with specific fungal targets, have been registered and released in the commercial market with different fungal pathogens as targets. However, these have not yet achieved their full commercial potential due to the inherent limitations in the use of living organisms, such as relatively short shelf life of the products and inconsistent performance in the field. Different mechanisms of action have been identified in microbial biocontrol of fungal plant diseases including competition for space or nutrients, production of antifungal metabolites, and secretion of hydrolytic enzymes such as chitinases and glucanases. This review focuses on the bacterial chitinases that hydrolyze the chitinous fungal cell wall, which is the most important targeted structural component of fungal pathogens. The application of the hydrolytic enzyme preparations, devoid of live bacteria, could be more efficacious in fungal control strategies. This approach, however, is still in its infancy, due to prohibitive production costs. Here, we critically examine available sources of bacterial chitinases and the approaches to improve enzymatic properties using biotechnological tools. We project that the combination of microbial and recombinant DNA technologies will yield more effective environment-friendly products of bacterial chitinases to control fungal diseases of crops.

Keywords::

• Biocontrol
• chitinolytic bacteria
• chitinases
• fungal pathogens
• chitin

Acknowledgements

We thank the University Grants Commission—Center for Advanced Studies (UGC-CAS), the Department of Biotechnology—Centre for Research and Education in Biology and Biotechnology (DBT-CREBB) program of School of Life Sciences, and the Department of Science and Technology—Fund for Improvement of Science and Technology Infrastructure in Universities and Higher Educational Institutions (DST-FIST) program of the Department of Plant Sciences, University of Hyderabad, for the infrastructure support.

Declaration of interest

CN, AK, and KS thank Council of Scientific and Industrial Research (CSIR) and PVSRNS thanks DBT for the research fellowships, and ARP thanks DBT for the major research grant on cloning novel chitinases using metagenomic approach.