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University of Saskatchewan (1994)

Survival of Rhizobia in the semi-arid environment of the Canadian prairies

Feindel, David E.

Titre : Survival of Rhizobia in the semi-arid environment of the Canadian prairies

Auteur : Feindel, David E

Université de soutenance : University of Saskatchewan

Grade : Doctor of Philosophy (Ph.D.) 1994.

The environmental influences affecting survival of Rhizobium leguminosarum bv. viceae were investigated in laboratory, growth chamber, greenhouse, and field studies with and without its host pea plant (Pisum sativum L.). As a prerequisite to these studies an identification technique was developed to monitor specific rhizobial isolates following introduction into soil. Polyclonal antibodies were produced to selected rhizobial isolates, and following cross-adsorption were relatively specific for the isolate to which they had been produced. Cross-reactivity with indigenous rhizobia ranged from zero to 10%. An immuno-blot technique was developed using a selective medium to estimate the size of the total isolate-specific population in soil. An enzyme-linked-immunosorbent assay was developed to determine root nodule occupancy and, in conjunction with the most-probable-number technique, was used to estimate the size of the infective isolate-specific population, which is that portion of the total population that is able to nodulate pea. Selected seed-applied isolates, were detected in zero to 34% of the nodules in the tap root region in the first year. Introduced isolates varied in their ability to compete with the indigenous population and were able to form zero to 16.3% of the nodules by the end of the second growing season. By the end of the third growing season, the introduced isolates formed up to an average of 6.3% of the overall infective population. Isolate C-1 was highly competitive, out-competing indigenous and other introduced isolates for nodule sites. Isolates which had been identified as superior N$\sb2$-fixers in controlled screening trials in the laboratory were not necessarily infective in a field situation. Soil mineral N, water soluble organic and inorganic carbon levels, length of the fallow period, soil texture, and soil moisture content did not inhibit R. leguminosarum survival under the experimental conditions of this study. Low soil temperature delayed nodulation and $\rm N\sb2$ fixation of pea. Freezing to $-$20 $\sp\circ$C and thawing reduced the total and infective soil rhizobial populations. The presence of a plant root system influenced seasonal fluctuations in the size of the soil rhizobial population. While some of the environmental conditions of the semi-arid region of the Canadian prairies were found to influenced the size of R. leguminosarum populations, none reduced survival.

Mots clés  : Agronomy, Ecology, nodulation, Microbiology, Biological sciences, Rhizobium leguminosarum

Accès au document : Proquest Dissertations & Theses

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