Beneficial microorganisms inhabiting different soils and plants are important determinants of soil fertility and plant health. Nitrogen-fixing rhizobia well known for symbiosis with leguminous crops is of crucial importance in organic farming. Besides being plant growth- promotion, rhizobia can also inhibit fungal pathogens. The antagonistic activities of 4 rhizobia isolates were tested in vitro in dual culture by concact and in vivo under greenhouse conditions against Fusarium oxysporum, the causal agent of Fusarium wilt. In dual culture, the 4 isolates inhibited the mycelial growth of the pathogen more than 60 % and the most effective were EP1 and EP72, which inhibited fungal growth more than 90 %. The four isolates viz. HBA1, EP1, SP32 and EP72 decreased significantly the disease index more than 60 % and increased peanut dry matter in greenhouse. The best protection against disease was obtained with isolates EP72, which reduced the percentage of wilted plants to less than 14 %. This study demonstrated e?ective biological control by the tested rhizobial isolates. More extensive studies are required to identify the native isolates of Rhizobium spp. and Bradyrhizobium spp. with dual functionality traits as biofertilizer as well as biocontrol of soilborne diseases agent for sustainable production of groundnut in South of Algeria.

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