Abstract: In this study, the effect of citronellal on the synthesis of ergosterol in the spores of imazalil-sensitive (Pds01) and imazalil-resistant (Pdw03) strains of Penicillium digitatum was investigated. The results showed that citronellal significantly inhibited the spore germination of Pds01 and Pdw03 with half maximal inhibitory concentration (IC50) of 0.8 and 3.2 µL/mL, respectively. Citronellal at its IC50 significantly decreased and increased the contents of ergosterol and lanosterol in Pds01 and Pdw03 spores, respectively. The expression of key genes involved in ergosterol synthesis was significantly affected. The up-regulated expression of the ERG9 gene in Pds01 peaked earlier than that in Pdw03, and the expression level of ERG3 was significantly down-regulated in both strains. This study showed that citronellal reduced ergosterol synthesis in Pds01 and Pdw03 spores by inhibiting ERG3 expression, thereby affecting spore germination, which could provide a theoretical basis for the development of green preservatives for postharvest citrus diseases.

Key words: Penicillium digitatum; citronellal; spore germination; ERG3 gene; ergosterol