MULTI-TRAITS OF NON-PATHOGENIC FLUORESCENT PSEUDOMONAS AND EVALUATION OF THEIR POTENTIEL AS BIOCONTROL AGENTS

Abstract

In recent years, certain strains of fluorescent pseudomonads called PGPB have drawn attention due to their abilities to promote plant growth. Therefore, in this investigation, we have explored the adhesive properties, the phytostimulator effects and the biocontrol activities of 40 isolates, with the aim to select potential inoculants to improve crop yields. Ten different colony morphotypes were detected on CRA plates. PsTp172 described as "ST" showed the highest adherence ability to abiotic surface (OD₅₅₀ = 2.102). 31 isolates were positive for the plant growth-promoting hormone (IAA) production and 30 stains solubilised tri-calcium phosphate in Pikovskaya’s agar. Furthermore, the highest pyoverdine concentration was detected with PsTp172 strain (172.50 µM) under iron starvation conditions. This strain also exhibited a co-resistance against Zn²⁺ and Mn²⁺ and displayed high values of Minimum Inhibitory Concentrations (MIC) for each heavy metal. Additionally, among the tested isolates, eight strains (PsS15, PsTp172, PsS28, PsTp171, PsS31, PsS67, PsS18, PsS39 and PsS93) were found to be efficient antagonists against the 3 pathogenic strains and 6 isolates (PsS15, PsTp156, PsTp172, PsC54, PsTp171 and PsS102) were considered as lactone inhibitors of the 3 tested strains, as shown by their ability to inhibit the cellular communication. The majority of isolates showed various phytobeneficial traits and the most effective strains are P. putida (PsTp172 and PsS15) and P. mosseli (PsTp171).