Journal de pathologie végétale et de microbiologie

Abstrait

Endophytic Bacillus spp. from Wild Solanaceae and Their Antifungal Potential against Fusarium oxysporum f. sp. lycopersici Elucidated Using Whole Cells, Filtrate Cultures and Organic Extracts

Rania Aydi Ben Abdallah, Hayfa Jabnoun- Khiareddine, Sonia Mokni- Tlili, Ahlem Nefzi, Sined Medimagh- Saidana and Mejda Daami- Remadi

Six isolates of culturable bacteria, isolated from stems of wild Solanaceae species (Datura metel, Solanum nigrum, S. elaeagnifolium, and Nicotiana glauca), were assessed for their antifungal activity against F. oxysporum f. sp. lycopersici (FOL), the causal agent of the tomato Fusarium wilt. Blast analysis of 16S rDNA sequencing genes homology showed that the isolates belonged to the genus Bacillus (Bacillus cereus str. S42, B. tequilensis str. SV39, B. subtilis str. SV41, B. methylotrophicus str. SV44, B. amyloliquefaciens subsp. plantarum str. SV65, and B. mojavensis str. SV104). The mycelium growth of FOL was significantly reduced by 36 to 46% by diffusible metabolites and by 18 to 21% by volatile compounds. Cell-free cultures were found to be mostly active when issued from 4 days-old cultures where FOL growth inhibition significantly varied from 31.1 to 59.5%. Active metabolites present in the cell-free cultures were extracted with n-butanol and chloroform. Both organic extracts exhibited antifungal potential towards FOL higher than that induced by the two commercial products i.e. Bavistin® (50%, chemical fungicide) and Bactospeine® (16000UI/mg, biopesticide). This study clearly indicates that endophytic Bacillus spp. from wild Solanaceae species can be used as natural sources of bioactive metabolites towards FOL. Wild Solanaceae are frequent in Tunisia and were not explored as potent sources of candidate antagonistic bacteria. In view of the endogenous progress of the pathogen via the vascular tissues, the use of endophytic bacteria can suppress tomato Fusarium wilt disease.