Azospirilli of Uzbekistan Soils and their Influence on Growth and Development of Wheat Plants

Associative nitrogen-fixing bacteria have been isolated, which were related to Azospirillum genus, by their morphological–cultural and physiological–biochemical ability to grow in microaerophilic conditions, as well as by a number of phenotypic traits. They comprised two species, namely, Azospirillum brasilense and Azospirillum lipoferum. Azospirilli strains displayed a varying salt resistance on potato medium containing a range of NaCl concentrations from 100 to 800 mM. The decrease in the nitrogen-fixing activity of azospirilli was detected starting from 200 mM NaCl. The biomass of the inoculated local varieties of wheat, Unumdor Bugdoi and Karlik 85, in microvegetation experiments exceeded the biomass of control plants by 20–50%. During the vegetation, some azospirilli strains formed spontaneous nodules on the wheat roots.