Abstract
The most important disease of tomato is Fusarium wilt caused by Fusarium oxysporum f. sp. lycopersici (FOL). To control this disease, this study examined the combined use of bacterial bioagents and peppermint oil (PO). Seven bacterial isolates were collected from tomato plant rhizospheres and tested in vitro against FOL. The highest growth inhibition against FOL was shown by isolate No.3. This isolate was identified using 16S rRNA sequencing gene as Bacillus amyloliquefaciens (BA). Peppermint oil tested at different concentrations (1, 2, and 3%) against FOL mycelial growth in vitro showed the highest inhibition at 3%. The effects of BA, PO, and BA + PO in vitro on the seed germination and seedling vigor index of the tomato cv. 'Tala F1' was also tested. All "BA, PO, and BA + PO" treatments increased the percentage of germinated seeds and seedlings' main shoots and root length compared to control treated seeds. The BA, PO, and BA + PO treatments were further tested under greenhouse and field conditions with pre-treated seedlings in FOL-contaminated soil. Under greenhouse conditions, each treatment decreased disease severity compared to untreated seedlings. Under field conditions, pre-treatment of tomato seedlings with BA and PO treatments reduced disease severity greater than BA + PO in combination and the mock-treated plants (66.6% for BA, 66.6% for PO and 55.3% for BA + PO, respectively). These findings support the use of BA or PO as bio-control agents against F. oxysporum in tomato. The interplay between peppermint oil, B. amyloliquefaciens, F. oxysporum, and the host plant requires further study to identify the causative mechanism for this increased disease resistance.