First report of Penicillium ulaiense causing whisker mold on postharvest citrus fruits in Morocco

Between February 2024 and June 2025, surveys conducted in northwestern Morocco revealed citrus fruits (Citrus sinensis and Citrus × limon) showing atypical postharvest decay symptoms, characterized by dark, water-soaked lesions with zonation and coremia-like structures. These symptoms were detected at only two sites, with a low incidence of 1.6% in the orchard and 0.5% in market samples. Five fungal isolates were obtained from symptomatic tissues on potato dextrose agar (PDA). Morphological characterization identified all isolates as Penicillium ulaiense, based on colony and micromorphological features consistent with published descriptions. Two representative isolates (BH_B1 and BH_E2) were selected for molecular analyses. Sequencing of the ITS region and the β-tubulin (BenA) gene showed 99-100% identity with reference P. ulaiense sequences, and the concatenated alignment comprised 804 base pairs. Phylogenetic analyses placed the Moroccan isolates within a well-supported P. ulaiense clade, clearly distinct from closely related species such as P. italicum and P. expansum. Pathogenicity assays reproduced typical symptoms on C. sinensis fruits, with progressive lesion development and successful re-isolation of the pathogen, confirming its pathogenic role under experimental conditions. This study reports, for the first time, the occurrence of Penicillium ulaiense associated with postharvest whisker mold symptoms on citrus fruits in Morocco. It provides new insights into postharvest citrus pathogens in Morocco and establishes a basis for future investigations on the occurrence and epidemiology of this species.