Carvacrol exhibits direct antifungal activity against stem-end rot disease and induces disease resistance to stem-end rot disease in kiwifruit

Kiwifruit stem-end rot is a common post-harvest disease caused by Clonostachys rosea and Fusariam equiseti, which triggers rapid fruit decay and reduces the commodity value of the fruit. This study investigated the antifungal activity and mechanism of carvacrol against pathogens of kiwifruit stem-end rot and its ability to induce disease resistance in kiwifruit. The results showed that the minimum inhibitory concentration and minimum fungus concentration of carvacrol to Clonostachys rosea and Fusariam equiseti were 0.06 and 0.09 mg/mL, respectively. Carvacrol could significantly inhibit mycelial growth and spore germination. With the increase of carvacrol concentration, the release of nucleic acid, electrical conductivity, protein, soluble sugar, and lipid contents gradually increased. Propidium iodide staining showed that the membrane integrity of Clonostachys rosea and Fusariam equiseti mycelia treated with carvacrol was damaged. In addition, carvacrol treatment inhibited the spread of plaque diameter after inoculation with Clonostachys rosea and Fusariam equiseti, effectively improved the activities of disease-resistant enzymes during storage, promoted the accumulation of pathogenesis-related proteins chitinase and glucanase, and increased the content of total phenols and flavonoids. These results show the potential application of carvacrol to control kiwifruit stem-end rot disease.