The influence of plant growth–promoting rhizobacteria on growth and enzyme activities in wheat and spinach plants

Abstract

A pot experiment in a greenhouse was conducted in order to investigate the effect of different N2‐fixing, phytohormone‐producing, and P‐solubilizing bacterial species on wheat and spinach growth and enzyme activities. Growth parameters and the activities of four enzymes, glucose‐6‐phosphate dehydrogenase (G6PD; EC 1.1.1.49), 6‐phosphogluconate dehydrogenase (6PGD; EC 1.1.1.44), glutathione reductase (GR; EC 1.8.1.7), and glutathione S‐transferase (GST; EC 2.5.1.18) were determined in the leaves of wheat (Triticum aestivum L., Konya) and spinach (Spinacia oleracea L.), noninoculated and inoculated with nine plant growth–promoting rhizobacteria (PGPR: Bacillus cereus RC18, Bacillus licheniformis RC08, Bacillus megaterium RC07, Bacillus subtilis RC11, Bacillus OSU‐142, Bacillus M‐13, Pseudomonas putida RC06, Paenibacillus polymyxa RC05 and RC14). Among the strains used in the present study, six PGPR exhibited nitrogenase activity and four were efficient in phosphate solubilization; all bacterial strains were efficient in indole acetic acid (IAA) production and significantly increased growth of wheat and spinach. Inoculation with PGPR increased wheat shoot fresh weight by 16.2%–53.8% and spinach shoot fresh weight by 2.2%–53.4% over control. PGPR inoculation gave leaf area increases by 6.0%–47.0% in wheat and 5.3%–49.3% in spinach. Inoculation increased plant height by 2.2%–24.6% and 1.9%–36.8% in wheat and spinach, respectively. A close relationship between plant growth and enzyme activities such as G6PD, 6PGD, GR, and GST was demonstrated. Plant‐growth response was variable and dependent on the inoculant strain, enzyme activity, plant species, and growth parameter evaluated. In particular, the N2‐fixing bacterial strains RC05, RC06, RC14, and OSU‐142 and the P‐solubilizing strains RC07 and RC08 have great potential in being formulated and used as biofertilizers.

The Role of Soil Beneficial Bacteria in Wheat Production: A Review

“…The application of the combination of PGPR and mycorrhizal fungi alleviates the stress conditions, as reported by Nadeem et al, via the regulation of hormones, nutrition uptake and growth [124]. Similar outcomes have been reported by Cakmakci et al for wheat and spinach plants [77].…”

“…The highest concentration of IAA is produced by bacterial strain P. fluorescens and Kocuria varians [74]. Specifically for wheat, the positive effect of PGPR via IAA has been reported [75][76][77][78].…”

Isolation and characterization of plant growth-promoting rhizobacteria from wheat rhizosphere and their effect on plant growth promotion

“…This variation is attributed to the various biosynthetic pathways, location of the genes involved, regulatory sequences, and the presence of enzymes to convert active free IAA into conjugated forms (Patten and Glick, 1996). The production of IAA by bacteria isolated from rhizosphere of different crops, i.e., peanut, maize, wheat, and rice had already been reported in number of studies (Dey et al, 2004; Cakmakci et al, 2007; Mehnaz et al, 2010). The amount of IAA detected in the present study (with and without tryptophan) seems relatively higher than reported earlier, indicating that soils under investigation have bacteria that have the characteristics most commonly sought for use in growth enhancement of plants.…”

Diversity and metabolic potential of culturable bacteria from the rhizosphere of Turkish tea grown in acidic soils

“…Selected strains, which were high carbon utilizing and phosphate solubilizing strains belonging to B. cereus, B. subtilis, B. megaterium, Pb. polymyxa, P. fluorescens, P. putida, S. maltophilia and B. cepacia, have been reported as good phosphate solubilizers and plant growth promoters (Chen et al 2006;Çakmakçı et al 2007b;de Freitas et al 1997;Dias et al 2009;Hariprasad and Niranjana 2009;Hoberg et al 2005;Idris et al 2009;Poonguzhali et al 2006). The carbon utilizations of PSB were investigated by using a Biolog microplate to determine if there are differences in the carbon utilizations of selected strains of these species.…”