Pathogenicity and induced resistance in Larix kaempferi and Larix olgensis inoculated with Endoconidiophora fujiensis.

This article focuses on the pathogenicity of the ophiostomatoid fungus Endoconidiophora fujiensis, associated with the bark beetle Ips subelongatus, in two larch species cultivated in China: the introduced Japanese larch (Larix kaempferi) and the indigenous Larix olgensis. Through artificial inoculation of saplings and adult trees, the study found that E. fujiensis is highly pathogenic to both species but causes larger necrotic lesions and exhibits greater virulence in adult L. kaempferi compared to L. olgensis. The indigenous L. olgensis demonstrated earlier and stronger defense responses, including higher accumulation of defensive monoterpenes (e.g., myrcene, 3-carene, limonene) and earlier induction of defense-related genes such as catalase (CAT) and pathogenesis-related protein 1 (PR1). These findings highlight species- and age-dependent differences in resistance mechanisms and underscore the potential threat of E. fujiensis to larch plantations in China, providing a molecular and physiological basis for future forest disease management strategies.