The spring wheat variety Varyag whith high potential nitrogenase activity and the greater contents of chlorophyll in leaves and the active strain of the bacteria Azospirillum sp. 77, selected from the washed roots of the spring wheat variety Varyag, were used for creation of effective association “wheat – diasotrophs of genus Azospirillum”. Inoculation of wheat variety Varyag seeds with the bacterial suspension Azospirillum sp. 77 promoted the reliable increase of nitrogenase activity on roots of plants (by 46 %), content of chlorophyll in leaves (by 18 %) and structural parameters of wheat crop (weight of grain from 1 ear and weight of 1000 grains were increased as a result of inoculation by 16,5 and 16 % accordingly).

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The paper depicts the results of intervarietal variability study of winter wheat plants in controlled environment with varieties Albatross Odessa, Kiriya, Zolotokolosa, Lybid and Odeska 267 by their associative nitrogen fixation ability. The 5.6 – 13.7 – fold divergence between the varieties by given index was revealed. It was shown that intravarietal variability of winter wheat plants by their ability to stimulate associative nitrogen fixation occurs along with the intervarietal one. Populations intensity of a different genotypes characterized by high nitrogen fixation activity in root zone, stipulates high nitrogen fixation potential of variety. Among the studied varieties Zolotokolosa was selected as genetically homogeneous variety with high nitrogen fixation potential of rhizosphere microorganisms that can be recommended for use in breeding as a source with high capacity for associative nitrogen fixation. New winter wheat varieties with high nitrogen fixation potential can fully develop using not only mineral nitrogen fertilizers, but also interacting with associative nitrogen fixation microorganisms should partially replace mineral nitrogen with biological that, in turn, will guarantee a high yield quality and conservation of agricultural landscapes.

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