Studies on Formulating Phyllosphere Consortia and its Shelf Life

Abstract

Employment of biological solutions for crop production is required due to the rising costs and detrimental effects of fertilisers and pesticides. Plant growth-promoting (PGP) bacteria are known to enhance soil and plant health. The main aim of this study was to develop a consortium with a reduced number of microbial strains on a common medium for ease of multiplication and application. The microbial isolates used in the present study were collected from the Institute of Organic Farming (IOF), UAS, Dharwad. Different biochemical and functional characterization tests were conducted to evaluate their plant growth-promoting traits. Media were amended with standardized concentrations of additives such as Polyethylene Glycol (PEG), Glycerol and acetic acid. Compatibility between the isolates was tested by the cross-streak method and evaluated for shelf life under laboratory conditions by the dilution plate count method. The results showed that among 11 PGP bacterial isolates, all six actinobacteria and two PPFM isolates showed positive results for oxidase, catalase, HCN and siderophore production, while all three LAB isolates were positive only for HCN production. Among 11, 4 isolates showing the highest production of IAA, GA, in-vitro N2 fixation and with multiple traits were selected for further study.  All 4 isolates were found to be compatible. Among 11 Liquid formulations, 7 consortia containing multiple isolates and other 4 were formulated individually. Shelf life evaluations of consortia demonstrated that it was significant up to only 4 months in terms of population and survival. An effective formulation with a lesser number of strains contributing to multiple functions and with high bioefficacy is a desirable characteristic of microbial inoculants, was achieved in this study.