Use of bacterial biocontrol agents for the control of Fusarium oxysporum f.sp. Lycopersici (Fusarium wilt) in tomatoes

Fusarium oxysporum f.sp Lycopersici (Fusarium wilt) is a serious plant pathogen that can cause yield losses >80% in tomatoes. The disease is controlled mainly by use of synthetic pesticides, which may be harmful to both humans and the environment. In this study, the potential use of antagonistic bacteria was reported for the control of fusarium wilt. First, we isolated and characterized fungi from tomato plants with wilt symptoms. Analysis of the ITS gene indicated fungi from the genus Fusarium, Alternaria, Plectosphaerella , Aspergillus , Gibellulopsis , Trichoderma , Papiliotrema , Rhodotorula , Mucor , Ustilago , Sporothrix and Cumuliphoma . 20 bacterial isolates were then screened from soils collected around the tomato plants for antagonistic activity against F.oxysporum using soft agar overlay method. Bacterial isolates showing inhibition zone diameters >3mm and consistent in reducing mycelial growth of the pathogen were further characterized and subsequently used for field experiments which were conducted during the short rain season in 2021 and 2022. The isolates grew at an optimum salt concentration of 5 - 10 % (w/v), pH range of 5 - 8 and a temperature of 30°C. Phylogenetically, they were affiliated to Bacillus subtilis , Paenibacillus polymyxa , Brevibacillus laterosporus , Bacillus velezensis , Bacillus amyloliquefaciens and Paenibacillus poriae whereas one of the isolates was identified as Myroides odoratimimus . Results from the field experiments showed that all selected strains significantly reduced average disease incidence (mean ± SE) for both years on day 14 (14.4% ± 3.49), day 28 (15.9% ± 3.44) and day 42 (15.2% ± 2.825) respectively. Therefore, these isolates are good candidates for the development of effective biological control programs against F. oxysporum f.sp Lycopersici affecting tomatoes.