VOCs emitted from Penicillium digitatum-infected citrus fruit are associated with accelerated neighboring fruit deterioration and serve as indicators for rapid disease detection

Citrus green mold, caused by Penicillium digitatum , is one of the major postharvest diseases responsible for citrus fruit decay. However, it remains unclear whether volatile organic compounds (VOCs) emitted from infected fruit affect neighboring healthy fruit and whether they can be exploited for rapid disease detection. Here, we demonstrated that infected-fruit VOCs were associated with accelerated peel coloration and reduced firmness and calyx freshness in neighboring healthy fruit, thereby compromising fruit freshness and visual quality. Moreover, neighboring fruit also exhibited accelerated depletion of soluble sugars and organic acids, increased reactive oxygen species (ROS) accumulation, reduced antioxidant enzyme activities, and aggravated membrane lipid peroxidation, which may contribute to fruit decay. HS-SPME/GC-MS analysis revealed that the VOC profiles of infected fruit were dominated by terpenes, followed by oxygenated terpenes and alcohols, and exhibited stage-specific compositional changes during disease progression. These changes were effectively detected by selected electronic-nose (E-nose) sensors, five of which were highly responsive to infection-associated VOCs. Integrated correlation analyses further identified trans -carveol, α-terpineol, and β-myrcene as candidate VOCs closely associated with both sensor-response patterns and fruit deterioration phenotypes. Subsequently, a portable VOC-sensing prototype was developed and shown to respond to VOCs emitted from infected fruit before extensive lesion expansion under controlled conditions. Collectively, this study demonstrated that VOCs emitted from infected fruit were associated with quality deterioration and senescence in neighboring healthy fruit and could also serve as potential indicators for rapid monitoring of citrus green mold during storage.