(E)-2-Octenal, a natural flavoring ingredient, suppresses the growth of a prochloraz-resistant Penicillium italicum strain

Citrus is one of the most economically important fruit crops and is widely planted in Asia, Africa, and Europe. However, citrus fruit is prone to suffer several invasive fungal diseases, such as blue mold and green mold caused by Penicillium italicum and P. digitatum, respectively, through wounded peel during long-term storage and transportation (Dao, 2008). Currently, these diseases are controlled mainly by the application of synthetic fungicides. However, excessive and constant application of chemical fungicides has led to not only severe environmental pollution but also the occurrence and expansion of fungal resistance (Duan et al., 2018, Papoutsis et al., 2019). In addition, there is an increasing concern over consumers because the residues from the chemical fungicide would remain in the peel of citrus instead of biodegradation along with the promotion of fungicides. Due to the reduced validity of chemical fungicides, it is indispensable to discover more commercially feasible alternatives to inhibit fungicide-resistant strains. Recently, plant essential oils have been considered as a promising substitute for controlling blue mold due to their natural origin, biodegradability, low toxicity and high antifungal activity (Chen et al., 2019, Wardana et al., 2022). In particular, several studies supported that plant essential oils such as oregano, thyme, Ruta graveolens and its components could display considerable antifungal properties on some fungicide-resistant strains (Donadu et al., 2021, Sienkiewicz et al., 2012), and this was attributed to the multiple inhibition sites different from the chemical fungicides or improvement of susceptibly to toxic factors (Langeveld et al., 2014, Li et al., 2021a). In our previous study, cuminaldehyde at a concentration of 0.3 mL L?1 was illustrated to be able to inhibit the mycelial growth of an imazalil-resistant P. digitatum strain (Reymick et al., 2022). (E)-2-Octenal, a natural flavoring ingredient isolated from plant essential oil(E)-2-Octenal is a natural flavoring ingredient that was isolated from plant essential oil and commonly used in the food industry (Api et al., 2022). It is generally emitted by insects as a defensive volatile compound against predators or entomopathogenic infections (Ulrich et al., 2015). Its antifungal activity was also reported. Specifically, Battinelli et al., (2006) revealed that (E)-2-octenal could inhibit the growth of Trichophyton mentagrophytes and Microsporum canis to varying degrees by decreasing the activity of elastase, which is essential for fungal colonization. More recently, it has been demonstrated to completely inhibit the mycelial growth of Alternaria alternata, Botrytis cinerea, Penicillium digitatum and Aspergillus niger at a concentration of 0.5 mL L?1 and Sclerotium rolfsii at a concentration of 50 ?L L?1 (Liarzi et al., 2016, Liarzi et al., 2020). These results suggested that it might be an alternative to chemical fungicides in controlling postharvest diseases. Research to study the effect on Penicillium italicumHowever, to the best of our knowledge, there are no reports on the application of (E)-2-octenal to alleviate the progression of citrus blue mold and its underlying antifungal mechanisms against prochloraz-resistant P. italicum. Therefore, the objective of this study is to determine the commercial feasibility of (E)-2-octenal as an alternative to prochloraz against prochloraz-resistant P. italicum and its underlying antifungal mechanism by (1) isolating a prochloraz-resistant pathogen designated P. italicum XX5 from citrus fruit, (2) investigating the antifungal capacity of (E)-2-octenal against P. italicum by in vivo and in vitro assays and (3) elucidating the potential damage to the cell membrane and mitochondria. Summary of the resultsThis work aims to determine the antifungal potential of (E)-2-octenal, a component of plant essential oil, on the mycelial growth and disease incidence of a prochloraz-resistant strain of P. italicum isolated from an orchard in Luxi, Hunan Province, China. An in vitro assay revealed that the minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of (E)-2-octenal were 0.25 and 0.50 mL L?1, respectively. An in vivo assay showed that wax + 4 ? MFC (E)-2-octenal treatment could reduce the blue mold incidence in Ponkan fruit inoculated with P. italicum without impairing fruit quality. Scanning electron microscopy analysis illustrated that the mycelia of P. italicum were anomalously twisted and shrunken upon treatment with (E)-2-octenal. The primary antifungal targets were attributed to the cell membrane instead of the cell wall based on propidium iodide and calcofluor white staining results. In addition, (E)-2-octenal induced massive accumulation of reactive oxygen species in hyphae in a dose-dependent manner, leading to oxidative stress and dysfunction of energy and respiration metabolism. At the same time, the activities of phosphofructokinase (PFK) and pyruvate kinase (PK) were decreased in (E)-2-octenal-treated samples. Taken together, our present study suggested that (E)-2-octenal could exert its antifungal activity against P. italicum by damaging the function of mitochondria and may be a potential antifungal substance for an alternative to chemical fungicides. Sources(E)-2-Octenal suppresses the growth of a prochloraz-resistant Penicillium italicum strain and its potential antifungal mechanismsYuwei Luo, Xin Chen, Jin Xin Che, Yonghua Zhang, Qiuli Ouyang & Nengguo TaoPostharvest Biology and Technology,?Volume 205, November 2023, 112515https://doi.org/10.1016/j.postharvbio.2023.112515Picture,??DIO LA NARANJA EL NOMBRE AL COLOR O EL COLOR SE LO CEDI? A LA FRUTA?https://historiasdelahistoria.com/2015/11/15/dio-la-naranja-el-nombre-al-color-o-el-color-se-lo-cedio-a-la-fruta