OBJECTIVES

1. Breed seedless leucaena hybrids for production of high-value hardwood and other products;
2. Develop strategies for cloning leucaenas and koa (Acacia koa);
3. Characterize the genetic diversity of koa and heritability of breeding system, bole form, color, figure and resistance to diseases and pests;
4. Evaluate superior varieties and hybrids of leucaena and koa in yield trials at locations representative of plantation development in Hawaii.
   
   

APPROACH

1. Artificial hybridization among Leucaena spp. and among provenances of Acacia koa;
2. Vegetative propagation, include meristem cloning and rootsprout culture;
3. Evaluation of genetic resistance through inoculation of koa seedlings with cultures of Fusarium oxysporum;
4. Production and mensuration in yield trials for hardwood production on 10 to 20 year cycles of elite accessions of koa and leucaena.
   
   

PROGRESS October 1999 to September 2000

1. Leucaena Hybridization and Cloning: The 50 accessions of L. pallida collected in Mexico in 1997 under a USDA grant were carried to 3-year maturity and seeds harvested from elite trees for advanced breeding. A composite was developed and made available to scientists in Mexico and internationally. Results of cloning studies were published, indicating that L. pallida was the only species we could not vegetatively propagate, and weinstituted studies of clonability among advanced crosses of this and other species. Our experiences with heterosis in this genus were the subject of two publications that emphasized the superiority of both intra- and inter-specific F1 hybrids. Loss in productivity by F2 populations was considered too small in the polyploid L. leucocephala to be significant, and seed agencies encouraged to market these as hybrids. Private financial support was obtained to expand cloning of seedless triploids in this genus, and a seed orchard planted to create triploid hybrid seeds. 
   
   
2. Koa Characterization and Evaluation: The family collections of Acacia koa were expanded to about 500 at the Hamakua Station, and seeds harvested from selected trees for our first seed orchard. Several collections were from six-year old trees in the first planting at this Station in 1991. In close collaboration with scientists at Hawaii Agriculture Research Center, quantitative genetic evaluations of several traits are underway, with clear evidence of high heritability of limbiness and bole form in this species.
   
   

IMPACTS