Rhizobia isolated from forage legumes of an arid cattle rearing ecosystem in Holguín, Cuba. Morpho-cultural evaluation and nodulation (phase I)

Radical nodules of naturalized and native forage legumes of arid ecosystems in Holguin, Cuba (Desmodium canum, D. triflorum, Centrosema virginianum, Indigofera mucronata and Alysicarpus vaginalis). An amount of 20 isolates were conducted in order to identify them as rhizobia and determine their morphocultural and staining characteristics. Nodules were macerated and its content was cultivated in specific media. Likewise, plantlets of Macroptilium atropurpureum were inoculated for identifying isolates. From them, 11 were identified as rhizobia due to their genotype and their ability to form nodules in M.atropurpureum. Three groups of colonies with different morphological characteristics were formed, all of them with slow or very slow growth, as well as with alkali production in the medium, except an isolate that produced an acid and four without reaction. It can be concluded that the 11 isolates that formed three groups of slow growth belonged to the Bradyrhizobiaceae family. However, isolates of Alysicarpus vaginalis and Indigofera mucronata showed no characteristics as rhizobia. Most of the isolates come from Centrosema virginianum and it was observed that growth in all groups was slow or very slow. Nevertheless, colony diameter, acid or alkali production and gum formation had a sensitive variation among formed groups. It is suggested to carry out assays of phenotype and genotype, in order to determine more exactly their taxonomical position up to species level. Key words: forage legumes, phenotype, Bradyrhizobium