Heavy metal tolerant Pseudomonas protegens isolates from agricultural well water in northeastern Algeria with plant growth promoting, insecticidal and antifungal activities

Abstract

The application of plant growth-promoting bacteria (PGPB) with biocontrol activities as inoculants of crops plants against phytopathogenic fungi and insect pests provides a biological alternative to the use of agrochemicals. Two Pseudomonas sp. strains were isolated from agricultural well water in the area of Bejaia, northeastern Algeria, located rather closely to a lead mine deposit. The isolates S4LiBe and S5LiBe had 16S rRNA gene sequence similarities of 99.4% to 99.7% with Pseudomonas protegens CHAO T and other P. protegens strains. The phenotypic profiles tested with BIOLOG-GN2-microplates were very similar, but showed also some remarkable differences. The isolates S4LiBe and S5LiBe showed plant growthpromoting potential based on the production of the phytohormone indole acetic acid and siderophores and the solubilization of insoluble phosphate. In addition, they produced chitinase and other polymer degrading enzymes. Interestingly, while S4LiBe and S5LiBe were resistant against heavy metals (2.0 mM K2Cr2O7 and 3.0 mM CoSO4, HgSO4, CdSO4 8H2O and PbCl2), the reference strain P. protegens CHAO T was very sensitive to Hg 2+ and Cd 2+ and had lower tolerance towards Co 2+ and Pb 2+ . The isolates S4LiBe and S5LiBe were very active in mycelial growth inhibition assays against Botrytis cinerea, Verticillium dahlia, Fusarium graminearum, Aspergillus niger and A. flavus (growth inhibition between 88% and 48%). Furthermore, S4LiBe and S5LiBe showed effective insecticidal activities, when tested in the Galleria injection assay and they were tested positive for the insect toxin gene fitD alike the reference strain CHA0 T . Finally, inoculation of barley seeds with S5LiBe resulted in significantly stimulated germination rate and growth of seedlings, with increased shoot length, shoot and root fresh weight, shoot and root dry weight as compared to non-inoculated plants.Thus, the heavy metal tolerant isolates S4LiBe and S5LiBe harbor a diverse potential as beneficial bacteria for agricultural application. They may be very useful even in polluted soils for the stimulation of e.g. biomass crops. The demonstration of successful isolation from agricultural well water may open more ready access for a wide variety of this kind of beneficial bacteria for agricultural application.

Isolation and Identification of Endophytic Bacteria with Plant Growth Promoting Activity and Biocontrol Potential from Wild Pistachio Trees

“…Koo and Cho (2009) showed that Serratia plymuthica SY5 isolated from heavy metal contaminated soil had capacity for IAA production and root growth potential. A previous report also indicated that P. protegens strains can produce IAA and stimulate plant growth ( Bensidhoum et al, 2016 ). In our study there was no direct relationship between the IAA producing ability of strains and root growth promoting effects.…”

Cadmium and cadmium‐tolerant soil bacteria in cacao crops from northeastern Colombia

“…strain CdDB50). This genus is well recognized due to its heavy metal bioremediation ability (Bensidhoum et al 2016). We strongly recommend the use of Pseudomonas sp.…”

Isolation and identification of endophytic bacteria with plant growth promoting and biocontrol potential from oak trees

“…Previous reports also indicated that P. protegens (formerly P. fluorescens) strains had a high ability to solubilize phosphate or were able to produce IAA and siderophores, resulting in improved plant growth (Bensidhoum et al, 2016;Katiyar & Goel, 2003). The endophytic life strategy of Stenotrophomonas maltophilia strains with various plants and an ability to promote plant growth are also documented (Ryan et al, 2009).…”