Isolation and characterization of phosphate solubilizing bacteria and their co-inoculation efficiency on tomato plant growth and phosphorous uptake

Abstract

Plant growth promoting traits which include indoleacetic acid (IAA), ammonia, siderophore and hydrogen cyanide (HCN) production were assessed in two phosphate solubilizing bacterial (PSB) isolates (Pantoea agglomerans and Burkholderia anthina) and their effect on growth and phosphorous uptake of tomato plants was investigated with a pot experiment conducted under green house conditions. The pots were arranged in a completely randomized block design with three replications per treatment. The experimental plan was based on eight treatments that is: (1) Soil without tri calcium phosphate (TCP) and bacteria inoculation (control), (2) soil + TCP, (3) Soil + P. agglomerans, (4) soil + P. agglomerans + TCP, (5) soil + B. anthina, (6) soil + B. anthina + TCP, (7) soil + P. agglomerans + B. anthina, and (8) soil + P. agglomerans + B. anthina +TCP. Both strains showed positive responses for all the tested plant growth promoting traits. IAA production was 10 and 7.5 µg/ml respectively for P. agglomerans and B. anthina. Both strains produced >80% siderophore and they were considered as efficient siderophore producers. Under green house conditions, both strains remarkably enhanced plant height, root length, shoot and root dry weight, phosphorous uptake and available phosphorous content of soil compared to the control. The increases were more pronounced in co-inoculation of PSB strains with TCP. Based on the results, it could be concluded that the strains possess great potential to be developed as biofertilizers to enhance soil fertility and plant growth. However, their performance under field conditions should be assessed before being recommended for commercial applications.   Key words: Phosphate solubilizing bacteria, phosphate solubilization, plant growth promoting traits