Isolation and characterization of rhizomicrobial isolates for phosphate solubilization and indole acetic acid production

Abstract

Recently, public concerns regarding the use of agrochemicals have increased due to the environmental impacts and potential risks to human health. The application of beneficial microorganisms is a novel technology to improve plant health and productivity and has therefore been extensively studied as an alternative strategy for biocontrol. In our study, 122 microbial isolates were obtained from the rhizosphere of Panax ginseng and subsequently tested in vitro for phosphate solubilization and indole acetic acid (IAA) production. Pikovskaya's medium was used to estimate rhizomicrobial isolates to solubilize tricalcium phosphate [Ca 3 (PO 4 ) 2 ]. Among all the investigated strains, 82 % of rhizospheric fungi showed phosphate solubilization activity; however, only 57.1 % of the rhizobacteria isolates showed phosphate solubilization ability. For IAA production, 64.7 % of the tested rhizofungi isolates were able to produce the phytohormone; however, only 47.62 % of the rhizobacteria isolates exhibited IAA production. Among all investigated species, Pseudomonas fluorescence and Azotobacter chroococcum showed the highest phosphate solubility demonstrating 885.4 and 863.4 lg mL -1 , respectively. Mucor sp. produced 42.3 lg mL -1 of IAA in Czapek's tryptophan medium, and the highest fungal species to solubilize the inorganic phosphate (237.5 lg mL -1 ) was estimated by Penicillium sp. Rhizobacteria were more effective than rhizofungi in phosphate solubilization and IAA production. This study introduces some potent species in terms of phosphate solubilization and IAA production which could be likely to improve soils' quality and promote plant growth.

Evaluation of the plant-growth-promoting abilities of endophytic bacteria from the psammophyteAmmodendron bifolium

“…Among the endophytic bacteria-induced growth promoting mechanisms resulting from plant hormones, IAA is the most common and extensively studied phytohormone. Recent studies have shown that more than 40% of all endophytic or rhizospheric bacteria are able to produce IAA (Palaniappan et al 2010;Li et al 2012;Andrade et al 2014;Hussein and Joo 2015), which is in agreement with our results (Fig. 2).…”

Phosphate Solubilization by <i>Bacillus subtilis</i> and <i>Serratia marcescens</i> Isolated from Tomato Plant Rhizosphere

“…In other words, carboxylic and hydroxylic anions produced by phosphate solubilizing bacteria have high calcium affinity and therefore can solubilize more phosphorus than acidification alone [44]. Accordingly, there is a symbiotic relationship between plants and phosphate solubilizing bacteria [45] [46], as bacteria provide the soluble phosphate and plant roots provide carbon compound such as sugars [47].…”

Plant Growth-Promoting Rhizobacteria Improved Salinity Tolerance of Lactuca sativa and Raphanus sativus

“…Microorganisms that strongly produce IAA were previously isolated from the rhizosphere of Panax schinseng (ginseng plant) South Korea [13]. The bacterial strain cultures were activated in Tryptic soy agar (TSA) medium, pH 7.2.…”