ASSOCIATIONS OF SUGAR-BEET AND NITROGEN-FIXING BACTERIA IN-VITRO

The associations of four Azotobacter chroococcum strains (2, 5, 8 14) isolated from the rhizosphere with two sugar beet hybrids (Hy-11 and D ana) grown in vitro have been investigated. All tested strains caused an increase in dry mass of both hybrids almost proportionally to the n itrogen content in the medium. Plant nitrogen content was also higher in inoculated variants. The highest nitrogenase and glutamate dehydrog enase activities were in Hy-ll associated with strain 5 and in hybrid Dana associated with strain 8. These associations were the most effect ive in N-2-fixation 2 weeks after inoculation. The results showed spec ificity of individual strains with respect to individual hybrids.