Pseudomonas Case Study

3.5. Evaluation of Pseudomonas spp. as plant growth-promoting bacteria under salt stress

Four strains, Pseudomonas plecoglossicida, strain 24, Pseudomonas sp., strain 30, P. putida, strain 103 and P. fluorescens, strain 109 which are salt tolerant and have the following plant growth-beneficial traits: IAA production, phosphate solubilization, and ACC deaminase production were selected for maize growth stimulation under salinated soil.

For non-saline soil (NSS) treatment, strain 103, characterized as P. putida, was able to significantly increase plant development for all the analyzed parameters, except for root dry weight. Plants treated with strain 103 showed an increase in 16.65% of shoot length, 20.16% in root length, 61.20% in leaf area and 83.29% in shoot dry weight, when compared to the control (table 3). Strain 109 (P. fluorescens), significantly increased root dry weight in

(Table 2). In the same medium NBRIP used to isolate phosphate solubilizers, values ranging from 31.5 to 519 μg.mL-1 were obtained [41] and in the present study the observed amounts were even higher (26 to 1.735 μg.mL-1 (table 3). A positive correlation between in vitro phosphate solubilization activities of Pseudomonas sp. (LG) with an increase in P content in bean plants inoculated with this bacterium has been observed [42]. In our work, Pseudomonas spp. strains 24, 30 and 109 produced high levels of soluble phosphate (> 1,000 μg.mL-1) (Table 2) and significantly increased plant growth (Table 2). Strain 24 (P. plecoglossicida) had significantly increased root length whereas strain 30 (Pseudomonas sp.) increased shoot dry weight and strain 109 displayed an increase in shoot and root dry weight (Table 3). However, strain 103 (P. putida) which produced only 83 μg.mL-1 of soluble phosphate, was the most plant growth-stimulating bacterium in NSS (Table