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.
