P-676 - Applied disease screening and selection program for resistance to vascular wilt in Acacia koaia.

Tuesday, August 5, 2025

10:15 AM - 11:00 AM HST

Location: Exhibit Hall 3

Presenting author(s)

KA

Keith V. Adams, IV

Assistant Forester
Hawaii Agriculture Research Center
Waipahu, Hawaii, United States

Author(s)

ND

Nicklos Dudley

Head of Forestry Program
HARC
Waipahu, Hawaii, United States
JL

Jane Marian S. Luis

Assistant Professor
University of Hawaii at Manoa
Honolulu, HI, USA
OO

Olatubosun Ojo (he/him/his)

Graduate Assistant
University of Hawaii at Manoa
Honolulu, Hawaii, United States
JL

Jenna Lidua

Forestry Technician
Hawaii Agriculture Research Center
Waipahu, Hawaii, United States
TJ

Tyler Jones

Head of Tree Crops Program
HARC
Waipahu, Hawaii, United States

Abstract Text: Similar to Acacia koa in most morphological traits, Acacia koaia, the “dry-lands koa”, is listed as “Vulnerable” by the International Union for Conservation of Nature (IUCN) Red List (2003), likely owing to habitat loss, hotter and drier weather, and increasing fragmentation. Conservation is further challenged by Fusarium oxysporum f. sp. Koae (FOXY), the causal agent of Koa Wilt Disease. With populations dwindling across the major Hawaiian Islands, it is critical to expand genetic conservation and resistance screening. Screening methods have been established for A. koa and are used regularly at the Hawaii Agriculture Research Center (HARC). This trial aimed to evaluate FOXY resistance among 28 wild-collected A. koaia mother trees from the west side of Hawaii Island. Seedlings were grown at HARC’s Maunawili facility on Oahu and screened using soilless potting media inoculated with a composite of highly virulent FOXY isolates. Mortality was monitored over a 120-day period under controlled greenhouse conditions. At the time of writing, 20 of 28 families showed moderate to high resistance, with mortality ranging from 4%-54%. These findings are promising for statewide A. koaia conservation efforts and demonstrate that natural resistance to FOXY exists within dryland populations. The application of A. koa screening methods to A. koaia represents a novel extension of this approach, broadening resistance testing in Hawaiian endemic Acacia spp., contributing to our understanding of FOXY phytopathology, and supports disease-resilient reforestation in vulnerable dryland ecosystems.