Establishment of a Genetically Diverse, Disease-Resistant Acacia koa A. Gray Seed Orchard in Kokee, Kauai: Early Growth, Form, and Survival
Open Access
- 28 November 2020
- Vol. 11 (12), 1276
- https://doi.org/10.3390/f11121276
Abstract
Background and Objectives: Koa (Acacia koa A. Gray) is an economically, ecologically, and culturally valuable tree species endemic to Hawaii. A vascular wilt disease caused by the fungal pathogen Fusarium oxysporum f. sp. koae Gardner (FOXY) induces high rates of mortality in plantings and threatens native koa forests as well. Landowners are reluctant to consider koa for reforestation purposes in many areas due to the risk of mortality caused by FOXY. Producing seeds with genetic resistance to FOXY is vital to successful koa reforestation and restoration. The Hawaii Agriculture Research Center (HARC), with both public and private partners, operates a tree improvement program to develop wilt-resistant koa populations in Hawaii. The population genetics of koa is poorly understood and seed zones are evolving. Thus, HARC uses provisional seed zones based on genetic and biogeographic variables and has selected wilt-resistant koa populations that are locally found in Kokee, Kauai (eco-regions) of Hawaii. Materials and Methods: To make these selections, virulent FOXY isolates were used in previous seedling inoculation trials to evaluate resistance levels among koa families in greenhouse experiments, and the most resistant families were used in the field trial reported here. Results: In this trial, survival rates two years after planting varied by family, and ranged from 45% to 95%, but all resistant families had greater survival rates than the susceptible control (25%). The trial has been converted to a seed orchard. Conclusions: The higher survival rates of the families are encouraging and seeds coming from the orchard will improve the success of future restoration and reforestation efforts. Within these resistant families it was also possible to make some selections based on height, growth, diameter, and stem form. Thus, the establishment of a wilt-resistant seed orchard results in locally adapted, eco-region specific, disease-resistant koa seed that will allow for the restoration of this iconic species and provide plant material for commercial reforestation opportunities at the landscape level.Keywords
This publication has 11 references indexed in Scilit:
- Assessing the durability, stability, and usability of genetic resistance to a non‐native fungal pathogen in two pine speciesPlants, People, Planet, 2019
- The evolving threat of Rapid ‘Ōhi‘a Death (ROD) to Hawai‘i’s native ecosystems and rare plant speciesForest Ecology and Management, 2019
- Strategic Development of Tree Resistance Against Forest Pathogen and Insect Invasions in Defense-Free SpaceFrontiers in Ecology and Evolution, 2018
- Applying landscape genomic tools to forest management and restoration of Hawaiian koa (Acacia koa) in a changing environmentEvolutionary Applications, 2017
- Breeding trees resistant to insects and diseases: putting theory into applicationBiological Invasions, 2017
- Meeting Forest Restoration Challenges: Using the Target Plant ConceptReforesta, 2016
- Applied disease screening and selection program for resistance to vascular wilt in HawaiianAcacia koaSouthern Forests: a Journal of Forest Science, 2014
- CANOPY NODULATION OF THE ENDEMIC TREE LEGUME ACACIA KOA IN THE MESIC FORESTS OF HAWAIIEcology, 2004
- Dieback of Acacia koa in Hawaii: ecological and pathological characteristics of affected standsForest Ecology and Management, 2002
- Acacia koaSeedling Wilt Caused byFusarium oxysporumf. sp.koae,f. sp. nov.Phytopathology®, 1980