Koa cannot be grown in plantations due to wilt disease. No seed sources with assured resistance are available to growers. We appear to have made major genetic progress in breeding koa wilt resistance. Seed from these plus-tree orchards will be wilt-tested, and an orchard established for wilt-resistant progenies of superior form and growth rate.

Contact Dr. J.L. Brewbaker (brewbake@hawaii.edu) Phone: 808-956-7985 Fax: 808-956-3894 FUNDING has been provided to CTAHR for this research from the USDA Cooperative State Research, Education, and Extension Service Project HAW00809-M.

OBJECTIVES

1) Identify superior trees among half-sib progenies in CTAHRs two koa seed orchards and rogue for tree form and growth.

2) Evaluate tolerance of half-sib progenies from these trees to koa wilt (Fusarium oxysporum f.sp. koae).

3) Establish advanced, isolated seed orchard of wilt-tolerant second-generation progenies and market seed to growers.

APPROACH

Our two koa seed orchards at Hamakua were based on outstanding trees among 600 half-sib progenies evaluated since 1991. These orchards will be rogued and coppiced to provide superior composited seedstock. Seeds (half-sib) from all selected trees will be evaluated for tolerance to fusarium wilt in greenhouse. Outstanding progenies will be composited for new seed orchard in isolation (Hamakua or Mealani). Seed samples will be provided to Hawaii Forest Industry Association for island-wide performance tests. Subsequent seed harvests will be composited for marketing by Hawaii Foundation Seeds (TPSS Dept).

All of our koa trials (about 20) occur on the Hamakua Station, 700m elevation, on the Hamakua coast of Island of Hawaii. This Station is no longer accessible by normal vehicles, due to severe erosion of the 6 miles of dirt road up the mountain, and our one attempt this summer resulted in damage to pickup and abortion of our plans. We have a trip planned for Nov. 20, '06. We continue to analyze data of mortality due to wilt since the first planting in 1991. If conditions at Hamakua continue to erode, we must move our trials elsewhere.

It is presently unwise to plant koa as an economic crop in Hawaii, due to spectre of wilt devastation. If our newly bred varieties are highly tolerant of wilt, they could have great economic impact in jump-starting what is presently a dying industry.