in: BACTERIAL PRACTICES IN AGRICULTURE, Fatih Çığ, Editor, İksad Yayınevi, Ankara, pp.169-212, 2021
Beneficial microorganisms improve plant nutrition and increase plant growth directly and indirectly through several important mechanisms, including fixation of elemental nitrogen, solubilization and mineralization of organic/inorganic phosphate, potassium and zinc, production of siderophores, phytohormones, ammonia, salicylic acid, hydrogen cyanide and carboxymethyl cellulose, iron sequestration, producing hydrolytic enzymes like protease, chitinase, lipase, pectinase, and cellulose, and plant tolerance to abiotic and biotic stress by lowering host ethylene levels through hydrolysis of 1- aminocyclopropane-1-carboxylic acid (ACC) by ACC deaminase. In addition, they act by quorum sensing (QS), rhizosphere engineering, converting organic matter to biomass, reducing biofilm formation, colonizing the plant root, producing exopolysaccharides to improve aggregate, improving soil structure, and indirectly acting as a biocontrol agent by mechanisms such as inducing systemic resistance. As an alternative, the use of selected and developed effective bacterial inoculants can contribute to alleviating biotic and abiotic stress and improve yield and quality in tea by reducing production costs, and environment and other adverse impacts, as well as reducing and eliminating the use of chemical fertilizers and pesticides. Due to years of synthetic fertilizers, soil health has deteriorated, soil acidity has increased and yield and tea quality have decreased, as well as increased groundwater pollution, nitrate levels in drinking water, eutrophication, algal blooms, and 'dead zones' in coastal marine ecosystems as a result of nutrient loss caused by tea farming systems. Therefore, alternative biotechnological approaches and different agricultural practices have to be adapted to increase production and maintain long-term ecological balance in agroecosystem and soil fertility. This review discusses various microorganisms especially bacteria acting as PGPR, their ecology, screening strategies, working principles, applications for tea, and mechanisms and beneficial characteristics exhibited by them. This chapter is an effort to elucidate the concept of rhizobacteria and their interaction with tea plants, beneficial properties and mechanisms, with recent updates.