Effects of plant growth-promoting rhizobacteria strains producing ACC deaminase on photosynthesis, isoprene emission, ethylene formation and growth of Mucuna pruriens (L.) DC. in response to water deficit

Agricultural sustainability is an increasing need considering the challenges posed by climate change and rapidhuman population growth. The use of plant growth-promoting rhizobacteria (PGPR) may represent an excellent,new agriculture practice to improve soil quality while promoting growth and yield of important crop speciessubjected to water stress conditions. In this study, two PGPR strains with 1-Aminocyclopropane-1-Carboxylate(ACC) deaminase activity were co-inoculated in velvet bean plants to verify the physiological, biochemicaland molecular responses to progressive water stress. The results of our study show that the total biomass and thewater use efficiency of inoculated plants were higher than uninoculated plants at the end of the water stressperiod. These positive effects may be derived from a lower root ACC content (? 45 %) in water-stressed inoculatedplants than in uninoculated ones resulting in lower root ethylene emission. Furthermore, the ability ofinoculated plants to maintain higher levels of both isoprene emission, a priming compound that may help toprotect leaves from oxidative damage, and carbon assimilation during water stress progression may indicate theunderlining metabolic processes conferring water stress tolerance. Overall, the experimental results show that coinoculationwith ACC deaminase PGPR positively affects tolerance to water deficit, confirming the potential forbiotechnological applications in water-stressed agricultural areas.