Isolation, Screening, and Characterization of Plant-Growth-Promoting Bacteria from Durum Wheat Rhizosphere to Improve N and P Nutrient Use Efficiency

Abstract

The main goal of this paper was to select promising microorganisms which could potentially act as plant-growth-promoting bacteria (PGPB) for durum wheat of Foggia County. At this scope, a new statistical framework, based on multivariate analyses and the evaluation of the statistical distribution of each trait, was used. Four hundred and seventy-four isolates were isolated from the rhizosphere of durum wheat in Foggia County and preliminarily screened as a function of four target indices (ammonium production, siderophores production, P-solubilization, and nitrification). After this step, the number of strains was reduced and the remaining isolates were tested through a quantitative approach, to assess the production of IAA (indole acetic acid), P-mineralization, and nitrification. In this second step, the cut-off was based on the whole population trend by evaluating for each trait the medians and quartiles. As a result, 16 promising isolates were selected and identified by 16S rDNA sequencing (Bacillus, Pseudomonas, Stenotrophomonas, and Lysinibacillus). The last step of this research was a preliminary validation in a growth chamber on eight strains. As screening and simple indices, two quantitative measures were chosen. The main result was the selection of at least three isolates (6P, 20P, and 25A) for a future field validation. They increased biomass and height by respectively 50% and 25%.

Effect of Plant Growth Promoting Bacteria on the Growth of Wheat Seedlings Subjected to Phosphate Starvation

“…MG515463.1) were used in this experiment. As reported in Di Benedetto et al [32], 12A and 25A differed in their level of P-mineralization with strain 12A characterized by a two-fold higher P-mineralizing activity than 25A. In addition, 12A was also capable of IAA production.…”

“…Of the two tested strains, only 12A significantly increased root length, surface and biomass. Although both isolates are equally capable of solubilizing inorganic forms of phosphorous, 12A is also able to produce IAA and furthermore has a superior P mineralizing capacity compared to 25A [32]. The IAA production represents an important selection criterion for bacteria with regards to their application as bio-fertilizer for cultivated plants [1,36,37].…”

“…The isolates 12A and 25A were morphologically and biochemically characterized through phenotypic tests, as reported in Di Benedetto et al [32]. The main differences are summarized in Table 1.…”

“…For qualitative analyses, positive tests are reported with 1; negative with nd. Modified by Di Benedetto et al[32].…”

Streptomyces sp. strain TOR3209: a rhizosphere bacterium promoting growth of tomato by affecting the rhizosphere microbial community

“…After incubated at 30 °C for 48 h, colonies with different morphologies, especially those specific and dominant in the TOR3209 treatment were picked up for further purification. Subsequently, all the isolates were reserved in 20% (v/v) glycerol at − 80 °C and were tested for indole acetic acid (IAA) production, siderophore production and phosphate solubilization using the method of Benedetto et al 30 , and the nitrogen fixation was tested using the method of Batista et al 31 .…”