P-255 - Assessment of Acacia koa families for resistance against koa wilt

Koa (Acacia koa Gray) is a keystone species in Hawaii’s forests, valued for its ecological, economic, and cultural significance. Infection with koa wilt, caused by Fusarium oxysporum f. sp. koae (FOXY), has led to high mortality rates in field planting and native forests. Identifying koa families possessing natural resistance to FOXY is crucial for disease management and reforestation efforts. In this study, a controlled greenhouse trial was established at the Hawaii Agriculture Research Center’s Maunawili Breeding Station to screen koa populations for resistance or susceptibility to wilt. The trial consists of 60 koa families, each represented by six seedlings per treatment arranged in a randomized complete row-plot design, replicated four times. Seedlings were grown in cone-tainers filled with soilless potting mix supplemented with a composite of nine highly virulent FOXY isolates. Controls included a susceptible family grown without inoculum, a non-virulent FOXY isolate, and the composite inoculum. Disease progression was monitored weekly by assessing wilt incidence, severity, and other disease symptoms. Wilted plants were harvested, surface-sterilized, and plated on Komada medium to confirm FOXY infection. Preliminary data shows variability in disease response among families, indicating differences in resistance and survival. As data collection progresses, family-specific resistance patterns will aid in the selection of families for orchard and reforestation trials. Findings will also be used for the development of tools for early resistance detection in koa seedlings.