PGPR Traits of Rhizospheric Nocardiopsis Strains Isolated from Algerian Soils

The absence of control on the plants diseases has dramatic consequences on production and product quality. The control of plants diseases has been mainly carried out by the massive use of pesticides which had proven to be toxic not only for the pathogens and the plants, but also for the consumers. The major goal of current control plant diseases is the use biological control agents. This environmentally friendly alternative has therefore attracted a lot of interest and is increasingly being used. Rhizobacteria are considered as effective biological control agents. Among rhizobacteria that promote plant growth (PGPR), actinobacteria have strong capability in biocontrol against plant diseases. In this study, two strains of actinobacteria isolated from Algerian rhizospheric soils were identified and characterized. The isolates were tested against phytopathogenic fungi. They were examined for their ability to produce indole-3-acetic acid (IAA) with different concentrations of l-Trp. The in planta antagonism was carried out with radish seedlings and Streptomyces scabiei as pathogen. The results of polyphasic identification assigned the two strains to the genus Nocardiopsis. It was found that the Vic8 strain inhibited all the tested fungi (P ˂ 0.0001). The results of the in planta antagonism showed that the root length of infected seedlings increased significantly (P ˂ 0.0001) with the inoculation of the strain Vic8. Both strains produce IAA, its production by Vic8 was significantly and positively (P = 0.0014) correlated with l-Trp concentration. This study showed that the strain vic8 is promising and it exhibits antifungal activity, in planta antagonism against S. scabiei and IAA production.