The Impact of Essential Oils Derived from Citrus Species to Control Botrytis cinerea and Their Potential Physiological Actions

<i>Botrytis cinerea</i> is one of the phytopathogenic fungi of the greatest economic importance worldwide. Essential oils (EOs) have been proposed as a sustainable alternative to reduce the growth of phytopathogenic fungi. Nevertheless, few studies exist about its mechanisms of action. This study evaluated the antifungal activity of EOs from <i>Citrus reticulata</i>, <i>Citrus limon</i>, <i>Citrus sinensis</i>, and <i>Citrus paradisi</i> peels and their encapsulation inside solid lipid nanoparticles (SLNs). Accordingly, <i>Citrus</i> EOs were mainly constituted by monoterpene hydrocarbons, where limonene was the most abundant in all EOs. <i>C. reticulata</i> and <i>C. limon</i> EOs reduced the mycelial growth at above 54% after 96 h. The other EOs did not significantly impact the phytopathogen. <i>C. reticulata</i> EO increased the hyphae damage by 40%, but the spore germination was reduced by only 8.34%. It also significantly increased the pH, the electrical conductivity, and the release of intracellular absorbing material and soluble proteins in <i>B. cinerea</i> cultures. Contrary, the esterase, mitochondrial, and succinate dehydrogenase activities decreased at above 50%. <i>C. reticulata</i> EO into SLN reduced the mycelial growth of <i>B. cinerea</i> by 90-97%. These results show that the EO of <i>C. reticulata</i> alters the physiological and metabolic activities of <i>B. cinerea</i> to reduce its growth.