Esterase Activity from Venturia nashicola: Histochemical Detection and Supposed Involvement in the Pathogenesis of Scab on Japanese Pear

Conidia of Venturia nashieola were collected from naturally scab-infected leaves of Japanese pear. Conidiaderived esterase activity was detected histochemically during the course of infection in ungerminated conidia, germ tubes, appressoria and conidia exudates. The esterase activity derived from conidia was partly inhibited in vitro by the specific cutinase inhibitor o-methyl-o-butylo-( 3,5,6-trichloro-2-pyridyl)phosphate and by the serine hydrolase inhibitor diisopropylfluorophosphate. The specific cutinase inhibitor applied at a concentration of 1.5 ppm did not influence the germination rate of the conidia on pear leaves but reduced the formation of subcuticular fungal structures by 64%. It was concluded that cutinase activity from conidia of V. nashicola probably plays an important role in the pathogenesis of scab during the invasion process.