| Summary: | Essential oils represent novel alternatives to application of synthetic fungicides to control against seedborne pathogens. This study investigated seven essential oils for in vitro growth inhibition of the main seedborne pathogens of cucurbits. <i>Cymbopogon citratus</i> essential oil completely inhibited mycelial growth of <i>Stagonosporopsis cucurbitacearum</i> and <i>Alternaria alternata</i> at 0.6 and 0.9 mg/mL, respectively. At 1 mg/mL, <i>Lavandula dentata</i>, <i>Lavandula hybrida</i>, <i>Melaleuca alternifolia</i>, <i>Laurus nobilis,</i> and two <i>Origanum majorana</i> essential oils inhibited mycelia growth of <i>A. alternata</i> by 54%, 71%, 68%, 36%, 90%, and 74%, respectively. <i>S. cucurbitacearum</i> mycelia growth was more sensitive to <i>Lavandula</i> essential oils, with inhibition of ~74% at 1 mg/mL. To determine the main compounds in these essential oils that might be responsible for this antifungal activity, they were analyzed by gas chromatography–mass spectrometry (GC-MS). <i>C. citratus</i> essential oil showed cirtal as its main constituent, while <i>L. dentata</i> and <i>L. nobilis</i> essential oils showed eucalyptol. The <i>M. alternifolia</i> and two <i>O. majorana</i> essential oils had terpinen-4-ol as the major constituent, while for <i>L. hybrida</i> essential oil, this was linalool. Thus, in vitro, these essential oils can inhibit the main seedborne fungi of cucurbits, with future in vivo studies now needed to confirm these activities.
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