Root associated bacterial communities in tomato and their exploitation for PGPR and Biocontrol potential

Abstract

Plant associated rhizobacteria are a major source of potentially useful microorganisms with antagonistic effects against plant pathogens or plant growth-promoting activity. The present study focussed on a preliminary evaluation of the antifungal activity of 237 bacteria isolated from the rhizosphere soil samples healthy tomato plants. A total of 29 isolates which were found to inhibit F. oxysporum were selected further for the plant growth-promoting activity. Out of 29 isolates, 6 were found to be phosphate solubilizers, 16 isolates produced siderophore, all the isolates produced IAA and ammonia, 10 isolates positive for the zinc solubilization and all the isolates were negative for the potassium solubilization. It was also found that some bacterial strain showed weak inhibition but observed to possess fairly good plant growth-promoting activity. These findings were supported us to shortlist six strains namely 10NB47, 3MNA5, 3MK13, 6PNA17, 7MM11, and 7MK31for further studies. Among these isolates, strains 3MNA5 and 3MK13 exhibited plant growth-promoting traits and strong antifungal activity. Whereas the strain 10NB47 recorded an excellent phosphate solubilization index followed by 6PNA17 and 7MM11 observed to possess an extraordinary IAA production within a very short period. Strain 7MK31 showed strong antifungal activity, therefore finally selected for identification and characterization of an antifungal compound as well as exploring this strain as a potential biocontrol agent for controlling Fusarium oxysporum. newlineIn agriculture, Bacillus species are widely used to stimulate plant growth and act as an efficient and ecologically sound tool for protecting the plant from pathogens and other environmental stresses. In the present study, it was recorded that the plant growth-promoting (PGP) ability of bacteria isolated from the rhizosphere soil of the tomato (Lycopersicon esculentum). These isolates were identified as Bacillus species based on a 16S rRNA gene sequence analysis.