Effect of crop management on soil bacterial communities in organic and conventional farming systems. Elabed, N., Bouri, M., Rhouma, A., Ben Kheder, M., and M'Hamdi, M. (Tunisia)

Abstract

The aim of the present study was to assess the population of bacteria isolated from organic and conventional soils and to identify antagonistic ones with a potential antifungal activity against some pathogenic fungi (Rhizoctonia solani and Fusarium oxysporum). All cultivable bacterial isolates were evaluated for their antifungal activity and the most effective ones were identified based on 16S rDNA sequence analysis. The results showed that among a total number of 100 bacteria isolated from soil, eight isolates displayed antifungal activity against F. oxysporum and twenty four isolates had suppressed R. solani growth. The results indicated that tested bacterial species exhibited varying degree of antagonistic potential against pathogenic fungi which ranged from 22.7% using AB95 isolate to 77.2% with AB40 and AB8 tested against F. oxysporum and from 22.7% using AB51 and AB5 to 68.1% with AB75 and AB64 tested against R. solani. DNA sequencing reaction of purified PCR amplicon was carried out using 16sF and 16sR primers. Sequence alignment with the reference sequences of the databases using BLAST was performed. The most dominant genuswas Bacillus. Phylogenetic tree was built.

Keywords

• Antagonists
• antifungal activity
• bacteria
• conventional farming
• organic farming
• soil