ISSN:
1573-5036
Keywords:
Azospirillum amazonense
;
A. brasilense
;
N NR− mutant
;
Wheat
Source:
Springer Online Journal Archives 1860-2000
Topics:
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
Notes:
Summary Two experiments were performed to examine the effects of inoculation of field grown wheat with various Azospirillum strains. In the first experiment the soil was sterilized with methyl bromide to reduce the Azospirillum population and15N labelled fertilizer was added to all treatments. Two strains ofAzospirillum brasilense isolated from surface sterilized wheat roots and theA. brasilense type strain Sp7 all produced similar increases in grain yield and N content. From the15N and acetylene reduction data it was apparent that these increases were not due to N2 fixation. In the second experiment performed in the same (unsterilized) soil, twoA. brasilense strains (Sp245, Sp246) and oneA. amazonense strain (Am YTr), all isolated from wheat roots, produced responses of dry matter and N content while the response to the strain Sp7 was much smaller. These data confirm earlier results which indicate that if natural Azospirillum populations in the soil are high (the normal situation under Brazilian conditions), strains which are isolated from wheat roots are better able to produce inoculation responses than strains isolated from other sources. The inoculation of a nitrate reductase negative mutant of the strain Sp245 produced only a very small inoculation response in wheat. This suggests that the much greater inoculation response of the original strain was not due to N2 fixation but to an increased nitrate assimilation due to the nitrate reductase activity of the bacteria in the roots.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF02378857
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