Effect of exopolysaccharide producing bacteria on soil structure, water retention capacity and maize growth under water stress

Water stress is a major environmental stress that limits the growth and productivity of crops in arid and semi-arid regions of the world. Exopolysaccharide producing bacteria present in soil serve as an important tool to mitigate the effects of water stress in plants they form associations with plant roots and help to conserve water in root zone. In this context present study was planned to inoculate exopolysaccharide producing bacteria on maize crop grown under different water stress levels. The study was carried out in net house at Experimental farm of Institute of Soil and Environmental Sciences research area, University of Agriculture, Faisalabad. Exopolysaccharide producing bacterial strain was isolated from root rhizosphere of desert plant brought from ThaI-desert. Bacterial strains were identified qualitatively for exopolysaccharide production on RCV-glucose medium by mucoid colony formation and thread loop formation. Three Exopolysaccharide producing bacterial strains, two previously isolated pure strains (T1= Pseudomonas putida T2= Lactobacillus rossaie) along with the isolated strain (T3 = Strain Ml) were inoculated on two maize hybrids (V1= FH-985 and V2= NK-8441) grown under three water levels. Non-stressed water level W1= 100% of field capacity and two water stressed levels were W2= 75% of field capacity and W3= 50% of field capacity. The data regarding plant morphological, physiological and soil physical parameters were taken by using standard procedures. The data were analyzed by using analysis of variance with CRD under three factors and least significance difference test at 5% probability level to compare the treatment means. The analysis of data revealed that introduction of exopolysaccharide producing bacteria in soil increased water stable aggregates, soil moisture content percentage, soil organic matter, soil water retention capacity of root zone soil thus improving over-all soil health. Improvement in soil health of resulted in enhanced plant growth. Bacterial inoculation improved the plant morphological, physiological and biochemical parameters. Inoculation significantly increased the plant height, shoot and root length, leaf area, fresh and dry biomass, shoot and root fresh and dry weights, relative water contents and chlorophyll contents of maize hybrids in both non-stressed and stressed water levels. From above summarized results it can be concluded that exopolysaccharide producing bacteria enhance water availability to plants under low moisture conditions by improving the soil structure and water retention capacity of root zone soil.