Caractérisation de certaines souches de Rhizobia associés à la culture d’arachide (Arachis hypogaea L.) à haut potentiel de solubiliser le phosphore dans la région de Ghardaïa.

Abstract

To study the microsymbiotes associated with the cultivation of groundnut (Arachis hypogaea L) in the region of Ghardaïa. 15 samples of Rhizobia were isolated from groundnut plants growing in Sebseb, Jedid and Mansoura regions. The morphological tests show that 60% of the samples belong to the genus Rhizobium, which is characterized by their rapid growth and the acidifying effect on the YMA + BTB culture medium, while the remaining 40% are Bradyrhizobium by their slow-growing and alkaling effect. This is confirmed by phenotypic tests: nutritional, physiological and biochemical. The nutritional test revealed that the tested groundnut strains showed a similar assimilation of carbon sources as fast-growing and slow-growing strains. And for the nitrogen source, it has been observed that some amino acids can inhibit their growth. A broad resistence to NaCl, pH was noticed for all isolated samples. The fifteen samples of Rhizobia were tested for their ability to solubilize the inorganic phosphate TCP by using a PVK solid medium and it was found that all of them have very high solubilization potentials with solubilizing halos in the range of 10-35 mm in diameter. As a result, it can be said that the isolated strains have a high capacity of solubilizing Pi, which is a main advantage of using Rhizobium as a phosphate solubilizing microorganism this latter is useful for both the mobilization of phosphate and the Nitrogen fixation.