Streptomyces griseus Lac1: biocontrôle et propriétés promotrices de la croissance des plantes

Abstract

Biological control is considered as an alternative method to chemicals use, which constitute a danger to the environment and to humans. The use of several modes of action by an antagonist and its ability to adapt to the rhizosphere, contribute to that biological control becomes more sustainable than chemicals. The objective of the present work was to evaluate the in vitro and in planta antagonistic capacity of a rhizospheric actinobacteria strain Streptomycesgriseus Lac1, and the demonstration of its plant growth promoting characteristics (PGPR). In vitro antagonistic activity was tested against seven locally isolated phytopathogenic fungi and four plant pathogenic bacteria (Erwinia amylovora, Pectobacterium carotovorum, Agrobacterium tumefaciens and Streptomyces scabies). Also, this strain was tested for its in planta antagonist effect against S. scabies (on radish shoots placed in growth poutches). In this test, Lac1 antagonist strain and was inoculated at the same time as S. scabies, and also before and after 24 hours of inoculation by the pathogen. Root growth was estimated by WinRhizo software. The PGPR properties determined are the 3-indole acetic acid (assayed by HPLC) and the of siderophore production. the results show that this strain has a preventive and not a curative effect. Lac1 produces 3-indole acetic acid (AIA) in the presence of Trp as a precursor and the amounts produced depend on the Trp concentration. The siderophores produced are catechol type. This study showed that the Lac1 strain is promising because it has antibacterial and antifungal activities, exhibits in planta antagonism against S. scabies, in addition it produces AIA and siderophores.