Interactions of Azotobacter chroococcum, Azospirillum brasilense and Streptomyces mutabilis, in Relation to their Effect on Wheat Development

摘要

AbstractSingle or dual inoculation of wheat seedlings (Triticum aestivumL. cv. Sakha 69) withAzotobacter chroococcum, Azospirillum brasilenseorStreptomyces mutabilisin sterilized soil resulted in significant stimulation of their populations in the rhizosphere, compared with the initial values. Viable counts ofAzospirillumandAzotobacterdecreased in dual inoculations withAzotobacterorStreptomyces,and contrasted with those ofStreptomyces,compared with the results of single inoculation. Single and dual inoculations stimulated plant growth, significantly increased the concentrations of indole‐3‐acetic acid (IAA), P, Mg, N and total soluble sugars (TSS) in wheat shoots. Soil content of N increased by single inoculation withAzotobacterand all dual inoculations. Soil‐IAA significantly increased by all inoculations. Growth ofA. brasilensesignificantly inhibited by filtrates from 7‐day‐old cultures ofS. mutabilisthan fromA. chroococcum,in vitro. The biosynthesis of antibacterial substance(s) byAzotobactersignificantly decreased by supplementing their cultures with metabolic products fromA. brasilense,but were stimulated by metabolic products fromStreptomycescultures. All metabolic products significantly decreased the growth ofA, chroococcum, A. brasilenseandS. mutabilis,nitrogen‐fixation and biosynthesis of IAA in Achroococcum,whereas biosynthesis of IAA stimulated inS. mutabilis.Most of the measured parameters after exposure to the tested bacteria or their metabolites were significantly correlated. The significance of IAA, nitrogen fixation and antibacterial substances, produced by such agronomically beneficial bacteria in early wheat growth i