ACC-Deaminase, Phosphate-Solubilizing Pseudomonas Fluorescens Enhance Cotton Growth and Yield Under Phosphorus Deficiency Stress

This filed study reports the phosphorus (P) deficiency tolerance of cotton (Gossypium hirsutum L.) as affected by seed inoculation with phosphate-solubilizing Pseudomonas fluorescens containing ACC-deaminase activity under P deficiency stress. The experiment followed a randomized complete block design with split plot arrangement involving two factors and three repeats. Factor A comprised of two P levels, i.e. 0 (control) and 75 kg P ha-1 (recommended). Factor B included three rhizobacterial treatments, i.e. control (no rhizobacterial seed inoculation), seed inoculation with P. fluorescens having single activity of ACC-deaminase and seed inoculation with P. fluorescens biotype F with ACC-deaminase and P-solubilizing activities both. The soil involved was heavy in texture, non-saline, alkaline-calcareous and low in organic matter and NaHCO3-extractable P. Recommended P fertilization significantly (p <0.05 to 0.001) increased various parameters of cotton, i.e. plant height (10.5%), sympodial branches (52.2%), stem diameter (37.4%), number of bolls (26.2%), average boll weight (54%), seed cotton yield (36.3%) and P concentration (69.7). The ACC-deaminase rhizobacterial strains of P. flourescens, with or without phosphate-solubilizing activity, also increased various traits of cotton plants. This increase was in a range of 13.4% to 22.6% in case of Pseudomonas flourescens without phosphate-solubilizing activity and 21% to 35.6% (1.4 to 2.0 fold more) in case of Pseudomonas flourescens with phosphate-solubilizing activity. The significant (p <0.01) interaction of recommended dose of phosphorus and Pseudomonas flourescens with phosphate-solubilizing activity resulted in maximum increase in some plant traits of cotton, i.e. plant height (1.3 fold), average boll weight (2.5 fold), seed cotton yield (2.0 fold) and phosphorus concentration (2.4 fold). Both the rhizobacteria increased various plant traits of cotton irrespective of the phosphorus application rate. At both the level of phosphorus, Pseudomonas flourescens with ACC-deaminase and phosphate-solubilizing activities was more effective than its counterpart with only phosphate-sloubilizing activity only. Pseudomonas flourescens with dual activities was more effective in increasing plant height and number of sympodial branches at phosphorus deficient level while rest of the plant traits at adequate phosphorus level. The study concluded that Pseudomonas fluorescens with dual activities of ACC-demainase and phosphate solubilization can play significant role as a bio-inoculant to enhance cotton growth and yield under both the phosphorus deficient and adequate conditions.