Isolation and characterization of novel plant growth-promoting rhizobacteria (PGPR) isolates from tomato (Solanum lycopersicum L.) rhizospherical soil: A novel IAA producing bacteria

Abstract

Indole acetic acid (IAA) production is one of the distinctive traits of plant growth-promoting rhizobacteria (PGPR). Ten different rhizobacterial strains were isolated from the roots of tomato crops (Solanum lycopersicum L.), grown in Kuwait, and then screened for their plant growth-promoting abilities, with emphasis on IAA production. The isolated strains were identified by 16S partial r-RNA sequencing and further characterized by conventional biochemical tests. Based on the nucleotide sequence analysis and homology of the isolates, a phylogenetic tree was constructed. The plant growth-promoting abilities of the strains were determined by testing for ammonium production, hydrogen cyanide and acid production, growth in nitrogen-free media, phosphate solubilization, and IAA production. The potential IAA PGPRs were re-applied onto the rhizosphere of green-house grown tomato plants to determine their effects on tomato growth. The results have indicated that all isolated strains were able to produce indole acetic acid even without the presence of a tryptophan precursor.

The ability of bacteria from legume plant roots grown on former coal mining soil to produce Indole-3-Acetic Acid (IAA)

“…The results of previous studies showed that the rhizosphere bacterial isolates of the tomato plant had activity in producing IAA hormones even without the presence of a tryptophan precursor [12]. Similar research was also conducted previously by isolating bacteria from various soils which showed that Bacillus spp.…”

“…When viewed from the value of the ability to produce IAA, then when compared with research by Dewi et al [39] is relatively small because with the same concentration of tryptophan the highest IAA produced reached 158, 651 ppm. Another study indicated that all were isolated strains from tomatoes were able to produce indole acetic acid even without the presence of a tryptophan precursor [12].…”

Progress in Microbial Fertilizer Regulation of Crop Growth and Soil Remediation Research

“…The majority of PGPR generate indole acetic acid, which is essential for coordinating the host plant's and microbiota's interaction. In the rhizosphere, tryptophan (Trp), a substance found in root exudates, is exchanged between the plant-beneficial rhizobacterium and the host plant to facilitate communication [73]. As a signaling molecule that facilitates communication between Rhizobia and the host plant, tryptophan triggers PGPR to synthesize IAA through a variety of pathways [74].…”