Abstract
Penicillium expansum, a widespread filamentous fungus, is a major causative agent of fruit decay and leads to huge economic losses during postharvest storage and shipping. Furthermore, it produces mycotoxin on the infected fruits that may cause harmful effects to human health. This pathogenicity assay involves a stab inoculation procedure of P. expansum on apple fruit, an important experimental technique to study fungal pathogenesis. This assay can be applied to analyze the virulence of postharvest pathogen on other fruits such as orange, pear and kiwifruit.