Potential Threat of Ceratocystis lukuohia to kiwifruit

Ceratocystis species are responsible for causing ceratocystis wilt in forestry and agronomic crops across numerous countries. Some Ceratocystis isolates are host-specific, while others are multihost. In Brazil, ceratocystis wilt stands out as the most severe disease affecting kiwifruit (Actinidia spp.), posing a threat to other kiwifruit-producing countries where Ceratocystis species have not yet been reported infecting kiwifruit plants. Where Ceratocystis isolates from different hosts and countries can infect kiwifruit, it is important to implement biosecurity measures that prevent the introduction of these isolates into kiwifruit-producing areas. In the present work, we assessed whether C. lukuohia and C. huliohia, isolated from diseased ʻōhiʻa trees (Metrosideros polymorpha) in Hawaii, can cause ceratocystis wilt in kiwifruit cultivars. Inoculations of both species in rooted cuttings of Monty and Zesy002 cultivars showed that C. lukuohia can infect and cause wilt and death in both kiwifruit cultivars, while C. huliohia was not able to infect either kiwifruit cultivar evaluated. The finding that C. lukuohia can infect plant species outside the Metrosideros genus indicates that it is not a host-specific Ceratocystis species, underscoring the importance of assessing the pathogenicity of this fungal species to other agricultural and forestry crops in Hawaii and the Pacific Basin. This is the first work demonstrating that C. lukuohia is pathogenic and lethal to kiwifruit plants. Therefore, it is essential to prevent the introduction of this pathogen into kiwifruit-producing countries, especially those where native Metrosideros species coexist.