Research Plant Pathologist USDA Forest Service Hilo, HI, USA
Rapid ʻŌhiʻa Death (ROD), caused by the fungal pathogen Ceratocystis lukuohia, has led to the death of over one million ʻōhiʻa (Metrosideros polymorpha) trees across Hawaiʻi. The loss of this keystone species has severely impacted forest health and ecosystems. To combat this crisis, the ʻŌhiʻa Disease Resistance Program (ʻŌDRP), a collaborative effort between the US Forest Service, Institute of Pacific Islands Forestry, and the Akaka Foundation for Tropical Forests, aims to develop disease-resistant ʻōhiʻa trees for restoration. Over the past seven years, the program has collected germplasm (seeds and cuttings) from more than 200 mother trees, primarily from areas experiencing significant ʻōhiʻa mortality. These materials are propagated at the Hilo facility, with seeds from additional trees being collected continually. Seedlings are grown for two years before undergoing resistance screening trials through artificial inoculation in a greenhouse. To date, seven screening trials have been conducted, revealing considerable variability in mortality rates among clonal materials and progenies. Survivors from these trials are being outplanted at high ROD hazard field sites to assess long-term survival.Ongoing research focuses on refining the screening process to reduce variability, including testing different inoculum types, temperatures, and sites. The program aspires to transition from its research phase to operational status, enabling the development of genetically resistant ʻōhiʻa populations. The promising resistance observed thus far offers hope for restoring native forests and providing stakeholders with disease-resistant seed and plant material essential for conservation.
