Evaluation of the Plant Growth-Promoting Microorganisms Potential for Drought Alleviation in Wheat Plants

One of the main abiotic stresses that threaten the survival of wheat (Triticum spp.) is drought. The present work aims to evaluate the ability of different plant growth promoting microorganisms (PGPMs) to alleviate the effects of dehydration in wheat and to understand the mechanisms involved. Wheat seeds (Triticum aestivum L. ssp. cv. ‘Galera’) inoculated with the strains Priestia megaterium CD_FICOS_01, Peribacillus frigoritolerans CD_FICOS_02, Pseudomonas canadensis CD_FICOS_03, Azotobacter chroococcum CD_FICOS_04 or Pichia kluyveri CD_FICOS_05 were exposed to prolonged drought by water shortage after which agronomic parameters, biochemical markers of abiotic stress and expression of genes related to plant response to water stress were measured. The behaviour of the PGPM strains evaluated varied in alleviating plant water stress, allowing two groups to be differentiated. The application of strains CD_FICOS_01, CD_FICOS_02 and CD_FICOS_03 resulted in an enhancement of crop production, with increases in aerial fresh biomass of 59%, 18%, and 38%, respectively, compared to the control. These strains also stimulated ethylene and/or abscisic acid metabolism. In contrast, strains CD_FICOS_04 and CD_FICOS_05 were also able to promote mechanisms related to the plant response to abiotic stress (MDA, proline, H2O2), but did not exert any physiological effect at plant level. In fact, they reduced the yield, with decreases in aerial fresh biomass of 43% and 21%, and in aerial dry biomass of 33% and 20%, respectively.