Indigenous Plant Growth-Promoting Bacteria from Drought-Affected Hungarian Soils: Screening for Beneficial Traits and Abiotic Stress Tolerance

While numerous plant growth-promoting (PGP) microorganisms have been described, the identification and characterization of novel indigenous strains with multiple PGP traits and strong tolerance to abiotic stress remain important for the development of sustainable agricultural bioinoculants. We isolated 90 bacterial strains from drought-affected soils across Hungary and screened them for key PGP traits, including phosphate solubilization, nitrogen fixation, indole-3-acetic acid production, 1-aminocyclopropane-1-carboxylate deaminase activity and antifungal activity. Furthermore, stress tolerance against osmotic stress induced by polyethylene glycol and growth on varying pH levels were evaluated. Among the isolates screened, we focused on those that exhibited multiple plant growth-promoting characteristics together with high tolerance to drought and narrowed down the number of candidates to ten, which were examined in a seed germination test. Based on 16S rRNA gene sequencing, these ten isolates were identified and found to be predominantly Pseudomonas sp. Isolate 1379 was particularly noteworthy as it has exhibited the ability to perform all of the examined PGP properties. Moreover, isolates 0210, 0526, 0736, 1163, 1166, and 1272 displayed four of the five tested traits. It should be mentioned, however, that while maximum biomass was observed with isolate 1379, no significant differences were detected between seeds treated with any of the isolates compared to the uninoculated control during the maize germination test. Consequently, further validation of isolates will be performed under greenhouse and field conditions, with the ultimate goal of formulating an effective bioinoculant to enhance crop drought resilience.