Host range of Colletotrichum pyricola: an aggressive pathogen of eucalypts

Colletotrichum is a fungal genus, comprising many plant pathogens that pose a significant threat to agriculture globally, however, their diversity and host range on Australian native plants remain poorly understood. Colletotrichum pyricola, first described as a fruit rot pathogen of Pyrus communis (common pear) in New Zealand, has also been reported in Australia, but its broader host range and potential biosecurity risk remain unknown. In this study, pathogenicity bioassays revealed that Co. pyricola can infect a range of Australian natives, including Banksia burdettii, Clematis aristata, Eucalyptus caesia, and Leptospermum grandifolium, as well as fruit trees, Malus domestica (apple) and Persea americana (avocado). Detached-leaf pathogenicity bioassays using both wound and non-wound inoculation showed Co. pyricola was also able to cause disease symptoms on a range of eucalypt species (Angophora, Corymbia, and Eucalyptus). Additionally, the re-isolation of Co. pyricola from asymptomatic, non-wounded tissues and microscopic observation of appressoria support a latent or hemibiotropic lifestyle. Therefore, these asymptomatic infections may allow the fungus to persist undetected across hosts and environments, facilitating long-term dispersal. These findings expand the known host range and potential geographic distribution of Co. pyricola in Australia, highlighting the importance of understanding fungal pathogens in native plant communities.