Exopolysaccharide and Siderophore Production Ability of Zn Solubilizing Bacterial Strains Improve Growth, Physiology and Antioxidant Status of Maize and Wheat

Abstract

Zinc solubilizing bacteria can solubilize zinc oxide and make them available for plant uptake. Rhizobacteria were isolated and screened for exopolysaccharide (EPS) and siderophore production and plant growth promotion. The strains IUB2, IUB3, IUB6, IUB10 and IUB11 showed potential zinc solubilization and plant growth promotion. The maximum increase of 31% and 40% in shoot length was recorded by the strain IUB3 in maize and wheat, respectively. The strain IUB11 showed the maximum increase of wheat vs. maize; 29 vs. 32% and 40 vs. 39% in dry biomass and root length. Furthermore, maximum bacterial colonization of 53 × 105 CFU g-1 root in wheat found by IUB2. While in maize (81 × 105 CFU g-1 root) found in maize by IUB3. All the tested isolates showed positive results for the exopolysaccharides, siderophore, HCN, catalase, protease and cellulose-degrading activities. Only strains IUB2 and IUB10 showed positive results for phosphate solubilization. Moreover, these strains were identified as Bacillus subtilis-IUB2, Bacillus velezensis-IUB3, Bacillus subtilis-IUB6, Bacillus vallismortis-IUB10 and Bacillus megaterium-IUB1. Our study found that inoculation of the selected zinc solubilizing bacterial strains enhanced the growth of both maize and wheat crops. Hence these strains can be utilized as biofertilizers in future.