Plant-beneficial rhizobacteria for sustainable increased yield of cotton with reduced level of chemical fertilizers

Abstract

Traditional use of chemical fertilizers in agricultural production can not be over-emphasized, but with fertilizer costs going up, these need to be supplemented or substituted with biofertilizers. Twenty-two plant growth promoting bacteria (PGPB) isolated from cotton grown in Pakistani soils were selected to assess the range of growth promoting properties. Some important capabilities of practical utility shown by these strains were nitrogenase activity, indole acetic acid (IAA) production, P and Zn mobilization, 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase activity and siderophores production. Growth and yield of cotton plant was significantly increased by these bacterial inoculations with different reduced levels of nitrogen (N) and phosphorus (P) fertilizers under controlled conditions as well as in field trials of two years. Co-inoculation of Pseudomonas aeruginosa Z5 and Bacillus fusiformis S10 with half and 1/4th of the recommended N and P fertilizers improved the boll mass, lint and seed yield compared to un-inoculated controls. Fluorescence in situ hybridization (FISH) using domain, division and subdivision-level probes was employed in combination with confocal laser scanning microscopy for identification of cotton rhizosphere associated bacteria. The results of FISH were found to be in accordance with 16S rRNA sequence analysis. Here we demonstrate that the seed treatment of cotton plants with Pseudomonas aeruginosa Z5 (AY548952) and Bacillus fusiformis S10 (AY548956) can improve growth and yield parameters in cotton fields with reduced levels of chemical fertilizers. Pseudomonas aeruginosa Z5 was deposited to DSMZ German Culture Collection with accession no. DSM16519.