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Selection of Bradyrhizobium strains and provenances of Acacia mangium and Faidherbia albida : relationship with their tolerance to acidity and aluminium

Lesueur D., Diem H.G., Dianda M., Le Roux C.. 1993. Plant and Soil, 149 : p. 159-166.

This work was designed to determine the role of the acidity and aluminium stress in the selection of partners in the Acacia symbioses with relevance to the persistence of the microsymbiont Bradyrhizobium in the soil and the growth and nodulation of the host plant respectively. Fifteen strains of Bradyrhizobium from Acicia mangium and Faidherbia albida formed a very homogenous acid tolerant group as indicated by their ability to grow better in a medium at pH 4.5 than in a medium at pH 6.8. By contrast, a growth experiment using an acid liquid media (pH 4.5), containing different concentrations of aluminium successfully identified strains sensitive to aluminium toxicity, and those able to grow even in the presence of 100 microM AlCl3. Our results suggest that high amounts of aluminimium in the soil rather than acidity (pH 4.5) were a major soil factor for selection of Bradyrhizobium strains capable of establishing a permanently high population under natural conditions. Unlike the behaviour of the microsymbiont, grow.th and nodulation of Acicia mangium and Faidherbia albida were not affected by aluminium, even at 100 microM, but they might be significantly affected y medium acidity (pH 4.5) depending on plant provenances. It is therefore suggested that ability of the host plant to tolerate acidity stress should be taken into account first when screening effective Acacia-Bradyrhizobium combinations for use in afforestation trials. (Résumé d'auteur)

Mots-clés : faidherbia albida; acacia mangium; sélection; symbiote

Thématique : Biologie du sol; Production forestière

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