Phytohormone biosynthetic potential of different Rhizobium species

Abstract

Plants may not have optimum growth hormone production potential under suboptimal growth and environmental conditions. The exogenous application of microbes is a potential and economical source of plant hormones. A laboratory trial was performed to evaluate the hormone biosynthesis potential of several soil microbes. Rhizobium sp. (Rhizobium trifolii, Rhizobium etli, Rhizobium meliloti, Rhizobium ciceri, Azorhizobium caulinodans, Bradyrhizobium japonicum, Rhizobium vulgaris, and Rhizobium phaseoli) were isolated from root nodules of various legumes and were biochemically characterized. Absorption spectroscopy (535, 254 and 665 nm λ) was used to quantify indole acetic acid (IAA), gibberellin and cytokinin production of different Rhizobium species. B3 isolate of Rhizobium trifolii had yielded (14.54 and 21.37 µg mL-1) IAA equivalents without and with L-tryptophan (L-TRP) supplement, that was statistically at par with same species while significantly greater than other Rhizobium isolates. Gibberellin production was found statistically non-significant in all isolates. Rhizobium phaseoli (Vp1) yielded 1.68 µg mL-1 cytokinin that was at par with the same species isolates and with Rhizobium trifolii but was critically greater in amount than other species. It was concluded that Rhizobium plays a vital role in plant growth and development can produce auxin and gibberellins, but some could produce cytokinin. Keywords: Phytohormone, Biosynthesis, IAA, PGPR, Auxin, Gibberellins, Cytokinin

The potential of Burkholderia sp. form Zea mays roots as Plant Growth Promoting Rhizobacteria

“…This indicates that the PGPR treatment itself can influence plant gibberellin production, with or without L-TRP supplementation. These findings are in line with previous research by Shahzad et al (2022), which shows that PGPR can increase gibberellin concentrations in plants along with other hormones such as auxin, consistent with other studies (Feldman, 1980;Shahzad et al, 2022;Tsukanova et al, 2017). Furthermore, the higher siderophore concentration in the PGPR treatments with or without L-TRP indicates that PGPR treatments have the potential to enhance iron uptake by plants.…”

“…These findings are consistent with previous studies by Karnwal (2019), which demonstrate that the addition of L-TRP enhances PGPR colonization in plant roots. This improved colonization allows PGPR to interact more effectively with plants, facilitating the exchange of nutrients, hormones, and other biochemical signals between the two organisms (Chandran et al, 2021;Kalitkiewicz & Kȩpczyńska, 2008;Pac ocirc me et al, 2016;Shahzad et al, 2022;Tsukanova et al, 2017). As a result, this reinforced interaction can lead to greater increases in plant growth and productivity.…”

The Potential of Burkholderia sp. from Zea mays Roots as Plant Growth Promoting Rhizobacteria

“…This indicates that the PGPR treatment can influence plant gibberellin production, with or without L-TRP supplementation. These findings align with previous research by Shahzad et al [13], which shows that PGPR can increase gibberellin concentrations in plants and other hormones, such as auxin, consistent with other studies [13][14][15]. Furthermore, the higher siderophore concentration in the PGPR treatments with or without L-TRP indicates that PGPR treatments have the potential to enhance iron uptake by plants.…”

“…The significant differences in growth parameters between the PGPR treatments with and without L-TRP supplementation highlight the importance of understanding the mechanisms underlying this enhanced effectiveness. These mechanisms may involve a complex interplay between microbial-produced hormones, nutrient solubilization, and improved stress resistance facilitated by L-TRP [13,[25][26][27]. The findings suggest that incorporating L-TRP into PGPR treatments could be a viable strategy to enhance agricultural productivity, particularly for crops like maize that play a crucial role in global food security.…”