Bioefficacy of pumpkin (Cucurbita pepo L.), sage (Salvia officinalis L.), and sesame (Sesamum indicum L.) essential oils as defense inducers of faba bean against rust disease

This study aimed to evaluate pumpkin, sage, and sesame essential oils against faba bean rust in vitro and in vivo and verify the formation of some biochemical defense responses in plants against such disease. Gas chromatography–mass spectrometry analysis revealed the existence of several bioactive constituents, such as fatty acids, esters, alcohols, phenols, antioxidants, carotenoids, and steroids. In laboratory studies, these oils were tested at different concentrations on urediniospore germination of Uromyces viciae-fabae , the causal pathogen of faba bean rust. All concentrations of the tested oils significantly ( P ≤ 0.05) decreased the germination of pathogen urediniospores. Among the tested oils, pumpkin oil at 1000 µl/L was the most effective on urediniospore germination (36.00%), followed by Tilt fungicide at 500 µl/L (11.25%), compared to control (88.75%). In greenhouse and field experiments, applying these oils as a foliar treatment significantly reduced the disease severity of faba bean rust. The highest reduction in disease severity was observed in Tilt fungicide treatment (5.82%), followed by pumpkin oil (11.56%) in greenhouse trials during growing seasons 2018/2019. At the same time, applying these oils enhanced yield components, such as plant height, number of pods per plant, and 100-seed weight. Compared to untreated plants, total phenol content (TPC) and enzyme activity increased in treated plants with these oils, but the highest increase was obtained when sage oil was applied. Results indicated a positive relationship between the efficacy of oils and increasing TPC and enzyme activities in treated plants. This study highlighted the possibility of using these oils to control faba bean rust, which is considered an effective eco-friendly method.