Enzymatic Characteristics of Canker Pathogens in Apple and Pear Trees  

Fungal canker occurred in apple and pear trees causes severe symptoms such as bark splitting, peeling, and decline of tree vigor, leading to substantial economic losses. Nevertheless, the physiological characteristics of the causal fungi, particularly their extracellular enzyme activities, remain poorly understood. In this study, fungal pathogens were isolated and identified from stems and branches of apple and pear trees showing canker symptoms in several apple and pear orchards where fire blight controlled during the first half of 2025. From the identified species, 10 pathogenic species (Botryosphaeria dothidea, Cytospora ceratospaerma, C. mali, Diaporthe amygdali, D. eres, D. fukushii, D. sackstonii, Diaporthe sp., Didymosphaeria variabile, and Paraphoma chrysanthemicola) were selected and comparatively evaluated for their extracellular enzyme production on chromogenic media. B. dothidea, C. mali, and D. sackstonii exhibited strong skim milk-degrading activity, while Diaporthe sp. showed particularly high starch-degrading ability. The remaining species displayed moderate or weak activity on various substrates such as Avicel, polygalacturonic acid, D-(+)cellobiose, starch, carboxymethyl cellulose sodium salt, xylan, and skim milk. These findings provide a systematic characterization of the enzymatic properties of major canker pathogens of apple and pear trees in Korea and offer fundamental information that can contribute to understand pathogenesis mechanisms and developing effective strategies for disease management.