Performance of soybeans inoculated with multifunctional microorganisms under water-deficit stress

Abstract

Soybeans (Glycine max (L.) Merr.) are mainly grown in Brazil during the rainy season. However, there are typically periods of rainfall deficiency, which causes water-deficit stress to the crop. Plant growth-promoting rhizobacteria (PGPR) can help alleviate these stresses by inducing water deficit tolerance. The objective of this study was to evaluate the role of PGPR in enhancing soybean tolerance to water-deficit stress. Six PGPR isolates, two for induction of water-deficit tolerance (ESA 441, BRM 034008), two AIA-producing (Ab-V5, BRM 063574), and two phosphate solubilizing (BRM 063573, BRM 67205), and their combination were evaluated, for a total of 16 treatments. The experiment was conducted in a greenhouse using a randomized block design with three replicates. Effects were measured on gas exchange parameters (stomatal conductance, transpiration, internal CO2 concentration, and photosynthetic rate), growth parameters (shoot dry weight, root dry weight, root length, root surface area, root diameter, and root volume), and yield components (pod weight, number of pods, number of grains, and grain weight). Co-inoculation significantly reduces the effects of water stress on gas exchange, plant growth, and productivity compared to single inoculation. Notable combinations, such as BRM 063574 + BRM 67205 + BRM 034008 and BRM 063574 + BRM 063573 + ESA 441, improved root and shoot growth under stress conditions. Yield components also improved with co-inoculations, with combinations such as BRM 063574 + BRM 67205 + ESA 441 showing the highest efficacy. These results suggest that specific PGPR co-inoculations can improve soybean resilience to water deficit stress and promote better growth and yield.