Inoculation with Pseudomonas spp. Containing ACC-Deaminase Partially Eliminates the Effects of Drought Stress on Growth, Yield, and Ripening of Pea (Pisum sativum L.)*1

Two preselected plant growth promoting rhizobacteria (PGPR) containing 1-aminocyclopropane-1-carboxylate (ACC)-deaminase (EC 4.1.99.4) were used to investigate their potential to ameliorate the effects of drought stress on growth, yield, and ripening of pea (Pisum sativum L.). Inoculated and uninoculated (control) seeds of pea cultivar 2000 were sown in pots (four seeds pot−1) and placed in a wire house. The plants were exposed to drought stress at different stages of growth (vegetative, flowering, and pod formation) by skipping the respective irrigation. Results revealed that inoculation of peas with PGPR containing ACC-deaminase significantly decreased the “drought stress imposed effects” on the growth and yield of peas. Exposure of plants to drought stress at vegetative growth stage significantly decreased shoot growth by 41% in the case of uninoculated plants, whereas, by only 18% in the case of inoculated plants compared to nonstressed uninoculated control.Grain yield was decreased when plants were exposed to drought stress at the flowering and pod formation stage, but inoculation resulted in better grain yield (up to 62% and 40% higher, respectively) than the respective uninoculated nonstressed control. Ripening of pods was also delayed in plants inoculated with PGPR, which may imply decreased endogenous ethylene production in inoculated plants. This premise is further supported by the observation that inoculation with PGPR reduced the intensity of classical “triple” response in etiolated pea seedlings, caused by externally applied ACC. It is very probable that the drought stress induced inhibitory effects of ethylene could be partially or completely eliminated by inoculation with PGPR containing ACC-deaminase.