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 Dana) grown in vitro have been investigated. All tested strains caused an increase in dry mass of both hybrids almost proportionally to the nitrogen content in the medium. Plant nitrogen content was also higher in inoculated variants. The highest nitrogenase and glutamate dehydrogenase activities were in Hy-11 associated with strain 5 and in hybrid Dana associated with strain 8. These associations were the most effective in N2-fixation 2 weeks after inoculation. The results showed specificity of individual strains with respect to individual hybrids.