[Physiological and Biochemical Properties of Diazotrophs from a Root Zone of Wheat Near Isogenic Lines by Vrn Genes].

Some of biochemical properties of diazotrophs isolated from a root zone of plants of such wheat isogenic lines as Vrn-A1, Vrn-B1, Vrn-D1, and Mironovskaya 808 cultivar were studied in a three-year field experiment. The larger percentage of isolates (47-55 %) capable of nitrate reduction is typical for the root zone of plants of the lines with higher levels of nitrogen fixation - Vrn-D1 and Vrn-A1. Compared with the spring isolines the rhizosphere of plants of the winter cultivar has substantially higher percentage of diazotroph' isolates with proteolytic and amylolytic activities - 44 % and 75 % respectively. However, the percentage of the isolates capable of producing IAA-like substances in the root zone of plants of the cultivar was less - 53 %. The percentage of isolates capable of producing indole, isolated from the rhizosphere of plants of Vrn-D1 and Vrn-A1 lines, was less (33-35 %) than the same indices of plants of the Vrn-B1 isoline and winter cultivar. Obtained data concerning differences in the percentage of the isolates of diazotrophs with studied physiological and biochemical properties from the plant rhizosphere of isogenic by Vrn genes lines of wheat are supposed to be connected with the differences between the lines in root exudates rate and nitrogen fixation.

[Dynamics of diazotrophic bacteria number in the root zone of wheat Vrn lines isogenic by genes].

The number of diazotrophic bacteria and nitrogenase activity in the root zone of isogenic monogene-dominant Vrn lines were measured in the field experiments throughout their vegetation from tillering to heading. The total number of diazotrophic bacteria and nitrogenase activity in the root zone of these lines during this period were increased irrespective of their genotypes. The above indices of the winter cultivar (Vrn loci bottom recessive) were lower than those of the spring lines--Vrn-A1, Vrn-B1 and Vrn-D1. Plants of Vrn-B1 line have the lowest indices among the spring lines with the exception of some indices. This line plants flowered later than those of Vrn-A1 and Vrn-D1 lines. We hypothesized the differences between plants of these lines as to nitrogen fixation activity and the number of diazotrophic bacteria are mediately determined by Vrn loci through their effects on metabolism intensity and assimilate reflux in the form of root exudates, therefore the total number of diazotrophic bacteria and nitrogenase activity increases.