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Article

Establishment of a Genetically Diverse, Disease-Resistant Acacia koa A. Gray Seed Orchard in Kokee, Kauai: Early Growth, Form, and Survival

1
Hawaii Agriculture Research Center, Waipahu, HI 96797, USA
2
Department of Forest Engineering, Resources & Management, Oregon State University, Corvallis, OR 97333, USA
3
Department of Forest Ecosystems & Society, Oregon State University, Corvallis, OR 97333, USA
4
Dorena Genetic Resource Center, United States Department of Agriculture Forest Service, Cottage Grove, OR 97424, USA
5
United States Department of Agriculture Forest Service, Forest Health Protection, Vallejo, CA 94592, USA
6
Department of Agricultural Biology, Colorado State University, Fort Collins, CO 80523, USA
*
Author to whom correspondence should be addressed.
Forests 2020, 11(12), 1276; https://doi.org/10.3390/f11121276
Received: 30 October 2020 / Revised: 20 November 2020 / Accepted: 24 November 2020 / Published: 28 November 2020
(This article belongs to the Special Issue The Scientific Basis of the Target Plant Concept)
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. View Full-Text
Keywords: Hawaii; koa; wilt-resistance; ecoregion; seed orchard; survival; growth performance; stem form; whole tree biomass; Fusarium oxysporum Hawaii; koa; wilt-resistance; ecoregion; seed orchard; survival; growth performance; stem form; whole tree biomass; Fusarium oxysporum
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MDPI and ACS Style

Dudley, N.; Jones, T.; Gerber, K.; Ross-Davis, A.L.; Sniezko, R.A.; Cannon, P.; Dobbs, J. Establishment of a Genetically Diverse, Disease-Resistant Acacia koa A. Gray Seed Orchard in Kokee, Kauai: Early Growth, Form, and Survival. Forests 2020, 11, 1276. https://doi.org/10.3390/f11121276

AMA Style

Dudley N, Jones T, Gerber K, Ross-Davis AL, Sniezko RA, Cannon P, Dobbs J. Establishment of a Genetically Diverse, Disease-Resistant Acacia koa A. Gray Seed Orchard in Kokee, Kauai: Early Growth, Form, and Survival. Forests. 2020; 11(12):1276. https://doi.org/10.3390/f11121276

Chicago/Turabian Style

Dudley, Nicklos, Tyler Jones, Kaitlin Gerber, Amy L. Ross-Davis, Richard A. Sniezko, Phil Cannon, and John Dobbs. 2020. "Establishment of a Genetically Diverse, Disease-Resistant Acacia koa A. Gray Seed Orchard in Kokee, Kauai: Early Growth, Form, and Survival" Forests 11, no. 12: 1276. https://doi.org/10.3390/f11121276

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