Bacteria can protect your cup of tea
Endophytic actinobacteria, which are well-known producers of bioactive compounds as metabolites, has shown potential as a viable alternative for growth and disease management of Tea plantations.
Tea, which has shown a decline in production due to the erratic climatic conditions, specially in Northeast India, is also susceptible to various fungal pathogens and pests. This has resulted in the overuse of chemical pesticides and fungicides to increase tea production and yield, adversely affecting human and soil health.
Dr. Debajit Thakur, Associate Professor, Life Sciences Division, and his research group at the Institute of Advanced Studies in Science and Technology (IASST), an autonomous institute of the Department of Science and Technology (DST), explored culturable endophytic microorganisms associated with tea plants for developing bio formulations as an eco-friendly alternative to promote plant growth and control diseases with minimum use of chemical inputs in tea plantation.
They found that endophytic actinobacteria isolated from tea clones could act as potential biocontrol agents. They could inhibit the growth of several fungal pathogens, namely, Exobasidium vexans, Poria hypobrunnea, Fusarium oxysporum, Nigrospora sphaerica, Phellinus lamaensis, and Rhizoctonia solani that are known to cause major fungal diseases in tea plants.
In their study published in the journal Frontiers in Plant Science, the researchers reported the molecular genetic diversity of 88 endophytic actinobacteria, the largest taxonomic group in the domain of bacteria, associated with commercial tea clones planted in Assam and Meghalaya Tea estates. They screened the endophytic actinobacterial isolates to evaluate their beneficial role towards the host tea plant and found that the majority of them have the capacity to enhance plant growth through phytostimulation, biofertilization, and biocontrol.
The team found that the bacteria produce phytohormone indole acetic acid, which governs cell division and stimulates vegetative growth in plants, and 1-aminocyclopropane-1-carboxylate deaminase (ACCD) enzyme, which can alleviate plant stress in abiotic and biotic stress conditions and enhance plant growth.
Besides, actinobacteria help in biological nitrogen fixation and phosphate solubilization, which boosts soil fertility, and the ammonia they produce helps in improving plant health by suppressing the growth of fungal pathogens.
In addition, these endophytic actinobacteria associated with tea plants also produce extracellular enzymes chitinase, cellulase, amylase, protease, and pectinase, indirectly promoting plant growth and helping in host defense. Secretion of cellulase and pectinase by these endophytes aids in the penetration of these bacteria into plant tissue and helps establish a symbiotic relationship between them. The production of chitinase enzyme by the isolates helps in the degradation of fungal cell walls and aids in protection against fungal phytopathogens, thereby contributing to the biocontrol of fungal diseases.
In the nursery experiment, selected Actinobacterial strains significantly enhanced the shoot and root biomass, shoot and root length, and leaf number in host tea plants.
The eco-friendly alternative with growth-promoting and antifungal traits could minimize the use of chemical inputs for growth promotion and disease control in commercial tea plantations.
The Know-How package for the production of plant growth-promoting substances and bioactive metabolites by microbial bioformulation has been developed, and the liquid formulation is validated in commercial Tea Estates of Assam for the application against major foliar tea fungal diseases. The product has been very effective in controlling Fusarium Dieback, Black Rot (causal agent, Corticium sp.); Red Rust (causal agent, Cephaleuros sp. in both stem and leaf), and Mealy-Bud in commercial Tea Estates. The technology for the production of bioactive metabolites by microbial strains has been transferred by signing of an Agreement between the Institute of Advanced Study in Science and Technology and Green Harvest (India) Bio-Tech, a company based in Guwahati, Assam.