ACC deaminase producing Pseudomonas putida strain PSE3 and Rhizobium leguminosarum strain RP2 in synergism improves growth, nodulation and yield of pea grown in alluvial soils

Plant growth promoting rhizobacteria affects the overall performance of plants by one or combination of mechanisms. However, little information is available on how ACC deaminase secreting bacteria enhance crop production. The present study aimed at identifying ACC deaminase producing and phosphate solubilizing bacterial strains and to assess their plant growth promoting activities. Additionally, the effect of two ACC deaminase positive bacterial strains Pseudomonas putida and Rhizobium leguminosarum on pea plants was determined to find a novel and compatible bacterial pairing for developing efficient inoculants for enhancing legume production and reducing dependence on chemical fertilizers. The isolated bacterial cultures were characterized biochemically and by 16S rRNA sequence analysis. The plant growth promoting activities was determined using standard microbiological methods. The impact of P. putida and R. leguminosarum, on pea plants was determined both in pots and in field environments. Of the total 40 bacterial strains, strain PSE3 isolated from Mentha arvenss rhizosphere and RP2 strain from pea nodules produced ACC deaminase, solubilized insoluble phosphate, synthesized indole acetic acid, ammonia, cyanogenic compounds, exopolysaccharides and had antifungal activity. The dual inoculation of P. putida strain PSE3 and R. leguminosarum strain RP2 had largest positive effect and markedly increased the growth, symbiotic characteristics, nutrient pool and quantity and quality of pea seeds. The measured parameters were further augmented when inoculated pea plants were grown in soils treated with urea or DAP. A significant variation in the measured parameters of pea plants was observed under both pot and field trials following microbial inoculation but the bacterial cultures did not differ significantly in growth promoting activities. The results suggest that ACC deaminase positive bacterial cultures endowed with multiple potential can be targeted to develop mixed inoculants for enhancing pea production and hence, to reduce dependence on synthetic fertilizers.