An in vitro antagonistic activity evaluation of rhizobacteria against Fusarium oxysporum f. sp. radicis-lycopersici (Forl) isolated from the Algerian west.

Abstract

The use of biological antagonists is a promising technique for the protection of plants without having a fatal effect on the environment. The in vitro confrontation tests is an obligatory step for the selection of successful antagonistic agents, what has ends in our study to the selection of two rhizobacteria: Bacillus subtilis and Pseudomonas fluorescens, isolated from the rhizosphere of tomato healthy plants and which were tested for their in vitro inhibitive power against five isolates of Fusarium oxysporum f. sp. radicis-lycopersici (Forl). The results of the direct confrontation on different culture media demonstrated that rhizobacteria have an inhibitive effect on the pathogenic, while noticing a performance of P. fluorescens with an inhibition which varies between 73,77 and 80 %, comparing with 56,36 and 60,46 % for B. subtilis. The inhibition by volatile substances of P. fluorescens varies between 25 and 39,53 %, compared with 18,86 and 32,55 % by volatile substances of B. subtilis. Rhizobacterial cell-free supernatant showed an inhibition from the first until the seventh incubation day against the five fungal isolates, when mycelia growth reaches 5±0,2 cm in presence of P. fluorescens cell free supernatant, and it reaches 5,9±0,3 cm in presence of B. subtilis cell free supernatant compared with 8,5 cm on control plates without rhizobacteria cell free supernatant.