Abstract

This work deals with the taxonomy, ecology and antagonist properties of actinomycetesisolated from soils of 7 Saharan palm groves. These microorganisms constitute an important part of the microflora of non-saline soils, but their density is very low in saline soils, particularly when the electrical conductivity exceeds 4 mS/cm. Salinity is the major factor governing their distribution in regularly cultivated parcels. Seven hundred and eighty nine isolates were identified for 12 genera and attached presumptively on the basis of their phenotypic characteristics to about 90 species. The taxonomy, for some predominant species, was confirmed by 16S rRNA gene sequencing. The genus Streptomyces ispredominant (59.8%), outstripping Micromonospora (25.6%), Actinomadura (4.3%),Nocardia (3.0%), Nocardiopsis (2.5%) and Amycolatopsis (1.5%). Soil salinity plays an important role in the dominance of certain species of Streptomyces from which,Streptomyces griseoincarnatus is the most frequently isolated. The Micromonosporapredominate significantly in 6 of 28 analyzed samples; this is due to the fact thatMicromonospora fulvoviolacea is the most common species in the genus. The study ofantagonistic properties of isolated actinomycetes showed that Fusarium oxysporum f. sp.albedinis, pathogen of date palm, is inhibited by 15.0% of isolates belonging to the genusStreptomyces.

Key words: Actinomycetes, Saharan soils, taxonomy, ecology, antagonistic properties.