|LUIZ, BLAINE - University Of Hawaii|
|STACY, ELIZABETH - University Of Nevada Las Vegas, Las Vegas, Nv|
Submitted to: Forest Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/2020
Publication Date: 11/26/2020
Citation: Luiz, B., Stacy, E.A., Keith, L.M. 2020. Screening of Metrosideros polymorpha ('ohi'a) varieties for resistance to Ceratocystis lukuohia. Forest Pathology. 51(1). Article e12656. https://doi.org/10.1111/efp.12656.
Interpretive Summary: M. polymorpha trees in Hawai‘i are dying from a disease complex known as rapid ‘ohi‘a death (ROD). This study was the first step toward understanding if resistance to C. lukuohia infection exists in ‘ohi‘a and if the varieties of this foundation tree found on the Island of Hawai‘i respond differently to infection.
Technical Abstract: Stands of the landscape-dominant tree, Metrosideros polymorpha (‘ohi‘a) on the Island of Hawai‘i, HI., USA are dying from a disease complex known as rapid ‘ohi‘a death (ROD). Approximately 180,000 acres of forest have already been impacted by the disease, the majority of which is attributed to C. lukuohia, the more aggressive of the two Ceratocystis species responsible for ROD. Three isolates of C. lukuohia were compared for differences in virulence. Mean disease severity and mean number of days to death did not differ among the three isolates of C. lukuohia. A single isolate was selected for use in a resistance screening of 128 plants across four varieties of M. polymorpha occurring on Hawai‘i Island: incana, glaberrima, polymorpha, and newellii. Disease severity was lower in early-successional var. incana (38.84%) and riparian var. newellii (36.11%) compared to late-successional var. glaberrima (61.27%) and high-elevation var. polymorpha (70.27%). Var. incana and var. newellii also had the lowest mortality (63% and 77%, respectively) while var. glaberrima (86%) and var. polymorpha (100%) had the highest mortality. Eighty-five percent of the plants that died did so within 49 days post-inoculation and mean number of days to death was significantly higher for var. glaberrima (46) compared to var. polymorpha (31). The results of this preliminary study suggest that some form of resistance might be present in natural populations of at least one variety of M. polymorpha on Hawai’i Island and should be investigated more intensively.