P-Solubilizing Streptomyces roseocinereus MS1B15 With Multiple Plant Growth-Promoting Traits Enhance Barley Development and Regulate Rhizosphere Microbial Population

Abstract

Phosphate-solubilizing bacteria (PSB) have been reported to increase phosphate (P) content and plant growth. Their application in agricultural systems is an eco-friendly alternative strategy for limiting negative environmental impact of chemical fertilizers and increasing costs. Therefore, the aim of this study was to isolate and characterize new putative PSB to use as inoculum to enhance plant growth and increase P bioavailability in soil. Sixteen bacteria were isolated from Moroccan oat rhizosphere and were screened for their putative P-solubilization by semi-quantitative agar spot method. The two strains MS1B15 and MS1B13, identified as Streptomyces roseocinereus and Streptomyces natalensis, respectively, showed the maximum phosphate solubilization index (PSI = 1.75 and PSI = 1.63). After quantitative assay to determine phosphate solubilization activity, S. roseocinereus MS1B15 was selected for evaluating its putative plant growth promotion activities including production of siderophores, indole-3-acetic acid (IAA) and aminocyclopropane-1-carboxylate (ACC) deaminase, nitrogen fixation and antimicrobial activity against soil-borne plant pathogens. Under greenhouse condition, barley plants inoculated with S. roseocinereus MS1B15 significantly increased shoot and ear length as well as available phosphorus in ears and leaves and P and N contents in the soil. Overall results showed that the selected strain S. roseocinereus MS1B15 could represent a potential candidate as biofertilizer to increase plant growth as well as P uptake.

Differential Root Exudation and Architecture for Improved Growth of Wheat Mediated by Phosphate Solubilizing Bacteria

“…We observed that pH of the medium decreased as soluble P increased. This might be because P-solubilizing bacteria can secrete organic acids in a culture medium to degrade TCP (insoluble P source) in order to increase soluble P (Penn and Camberato, 2019;Chouyia et al, 2020). Among organic acids detected by HPLC acetic acid, gluconic and citric acids were predominantly produced by selected P-solubilizing bacteria (Table 1).…”

“…Besides making soluble P available for plant uptake, P-solubilizing bacteria are involved in plant growth promotion by the production of beneficial metabolites, such as phytohormones like indole acetic acid (IAA), antibiotics or siderophores, aminocyclopropane-1-carboxylate deaminase (ACC), nitrogen fixation, zinc solubilization, and antimicrobial activity against soil-borne plant pathogens (Olanrewaju et al, 2017;Chouyia et al, 2020;Kumawat et al, 2020;Hakim et al, 2021). Furthermore, plant growth-promoting rhizobacteria (PGPR) may indirectly stimulate plant growth and help the plants to alleviate oxidative stress by enhanced production of antioxidant enzymes [e.g., catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD)] in plant tissues (Batool et al, 2020;Bhat et al, 2020;Ha-Tran et al, 2021).…”

Seed bio-priming with tri-species consortia of phosphate solubilizing rhizobacteria (PSR) and its effect on plant growth promotion

“…PSM-2, Pantoea sp. S32 on TCP and other media were recorded by several groups [ 36 , 40 , 41 , 42 ].…”

“…[ 53 ]. Walpola and Yoon [ 42 ] recorded higher plant height and weight in tomato inoculated singly with P. agglomerans and Burkhoderia anthina or co-inoculated with both strains compared to un-inoculated plants. Similar finding were also recorded by Korir et al [ 23 ] that co-inoculation of rhizobia with other PGPR enhanced nodulation, plant weight of common bean over the control.…”

Bioformulations with Beneficial Microbial Consortia, a Bioactive Compound and Plant Biopolymers Modulate Sweet Basil Productivity, Photosynthetic Activity and Metabolites

“…and natural substances (humic acids, seaweed and plant extracts, protein hydrolysate and silicon) able to stimulate plant vigor, growth and yield, even in sub-optimal conditions. These exemplify a valid alternative to chemical products that do not threaten biodiversity, able to reduce harmful effects to human health and the environment by decreasing the use of synthetic fertilizers and toxic pesticides [ 18 , 19 , 20 , 21 ]. The beneficial microorganisms that can be used as biostimulants include fungi such as Trichoderma spp.…”