A framework for establishing a rapid ‘Ōhi‘a death resistance program

Abstract

Metrosideros polymorpha Gaud. (‘ōhi‘a) is the most abundant native forest tree in Hawai‘i and a keystone species of cultural, ecological, and economic importance. ‘Ōhi‘a forests, particularly on Hawaiʻi Island, are being severely impacted by Rapid ‘Ōhi‘a Death (ROD), which is caused by the fungal pathogens Ceratocystis lukuohia and C. huliohia. ROD is characterized by branch dieback, crown wilting, and mortality. Initial disease resistance screening of four varieties of M. polymorpha with C. lukuohia demonstrated that varieties may differ in susceptibility. Several survivors of field or screening-based infections still exist, providing strong impetus for the establishment of the ‘Ōhiʻa Disease Resistance Program (ʻŌDRP). Here, we outline a framework for guiding the ʻŌDRP throughout the process of identifying and developing ROD resistance in M. polymorpha and, possibly, all Hawaiian Metrosideros species. Core ʻŌDRP projects include: (1) evaluating and operationalizing methods for greenhouse-based production and screening of test plants; (2) greenhouse screening of seedlings and rooted cuttings sampled from native Metrosideros throughout Hawaiʻi; (3) establishing field trials to validate results from greenhouse assays; (4) understanding environmental and genetic drivers of resistance to characterize the durability of resistance to ROD; (5) developing remote sensing and molecular methods to rapidly detect ROD-resistant individuals; and (6) conducting breeding trials to improve the degree and durability of ROD resistance. Ultimately, the ʻŌDRP seeks to produce ROD-resistant material for the perpetuation of M. polymorpha across Hawai‘i, with the goal of preserving the ecology, culture, and communities that are dependent on this tree species.

Redbay (Persea borbonia L. Spreng) Seedling and Sapling Growth and Recruitment Near Trees with and without Putative Resistance to Laurel Wilt Disease

“…Identifying the genes responsible for laurel wilt resistance in redbay and their durability will allow for selective breeding efforts to be undertaken effectively [33,45]. Finally, as with other species that have been affected by invasive species, the outplanting of disease-resistant redbay germplasm should commence on a wider scale, and reforestation potential should be evaluated, specifically to determine if individuals that have performed well in laboratory trials can withstand disease pressure in the field throughout all phases of their life cycle [34,46]. Silvicultural guidelines to ensure seedling survival should be identified.…”

“…], and ' ōhi'a (Metrosideros polymorpha Gaudich. ), the discovery of disease resistance can provide an opportunity to restore species that are unable to naturally regenerate effectively due to overwhelming pathogenic pressure [8,[32][33][34]. While the deployment of resistant hosts has been suggested as a plausible management strategy [28], studies on the long-term survival of resistant redbays in situ are non-existent.…”

Screening of Persea borbonia clones for resistance to the laurel wilt pathogen, Raffaelea lauricola

“…Persea borbonia genotypes inoculated with Raffaelea lauricola in farm plot disease resistance trials. from heavily impacted sites for initial germplasm collection (Flower et al, 2017;Griffin et al, 2005;Houston, 1982;Luiz et al, 2022). We opted to collect vegetative material for propagation and subsequent screening since long-term storage of seeds is problematic due to a high lipid content (V. Vankus personal communication).…”

A Five-Step Framework for Creating Forests for the Future

“…To uphold the forest renewal process, science and forest practices have also developed a lot of frameworks, supporting plantation forestry, regular stand renewal, and restoration due to different disturbances [34][35][36][37][38]. The latest concepts in row are forest landscape and ecological restoration.…”