First report of Penicillium italicum causing blue mold on mandarins (Citrus reticulata) in Vietnam, highlighting differential sensitivity to hydrogen peroxide

Abstract

Penicillium italicum is the primary postharvest pathogen of citrus blue mold worldwide. However, it has been rarely documented in tropical regions. This work aimed to report the occurrence of P. italicum strains in Vietnam for the first time. Two fungal strains were obtained from blue mold-infected mandarins collected in Hanoi city. Based on morphological characteristics combined with molecular identification using the rDNA internal transcribed spacer (ITS) region and the benA (β-tubulin) gene, these isolates were identified as P. italicum. Pathogenicity assays confirmed that both isolates induced blue mold symptoms on mandarins. The isolates showed reduced growth at 30 °C relative to 25 °C, indicating their lower-temperature preference comparable to that of the major citrus green mold pathogen P. digitatum. Notably, in contrast to P. digitatum, both P. italicum isolates were highly sensitive to hydrogen peroxide (H₂O₂)-induced oxidative stress. Our study provides foundational insights for future investigations into the molecular pathology and management of postharvest citrus losses caused by this pathogen in tropical regions.