Are We There Yet? The Journey Toward Koa Tree Improvement

Transcription

1 Are We There Yet? The Journey Toward Koa Tree Improvement

2 What Needs Improving 1. Yield of Merchantable Wood Gross wood volume at harvest Stem form Fork height (apical control) Growth rate Photosynthetic efficiency Allocation pattern

3 Typical Stem Form of Plantation Koa Assumed target volume = 9,565 bf/ac Goldstein et al Spacing: 7 x 9 ft Density (stems/ac): All initially 691 All at 18 yrs 170 D&C only 114 Crop only 10 Est. 45-yr yield (bf/ac): D&C only 5,615 Crop only 1,100 Volume shortfall (%): D&C only 41 Crop only 88 Scowcroft et al. Small-scale For. 9:

4 Stem Form s Not Much Better for Naturally Regenerated Koa Dense Patches (>250/ac) Clean boles Average butt-log length, 7.5 ft 5 10 crop trees/ac treated Crop tree log length, 14.8 ft 21-years old at Hakalau NWR

5 What Needs Improving (cont.) 1. Yield of Merchantable Wood Net wood volume at harvest Occurrence of defects Proportion of heartwood Wood quality (color, grain, figure)

6 Large Gross Volume, But Low Net Volume Due to Multiple Defects Seams Bark pockets Flutes Holes Hidden decay

7 Defects Type of defect Percent of logs * Seam 61 Branch stub 57 Ring shake 36 Double pith 32 Heart check 28 Bark pocket 28 Flute 14 * 28 logs sampled Wiedenbeck & Lowell. Koa quality study, project accomplishment report (on file IPIF)

8 Desirable Wood Quality #1 Common, flat-saw, 25-yr-old, second-growth koa from Kona-Hema Photographer: Elaine Murray Shafto & McDaniel. (With permission) Contemporary Hawaii Woodworkers: the Wood, the Art, the Aloha

9 What Needs Improving (cont.) 2. Disease Resistance Vascular wilt disease Heart rot Wood decay fungi

10 Koa Vascular Wilt Up to 95% mortality in young plantations Symptoms: terminal branch dieback, staining of wood, weeping, bark cankers, death

11 What Needs Improving (cont.) 3. Insect Resistance Acacia psyllid Black twig borer Koa looper

12 The Acacia Psyllid

13 The result bushy trees with multiple, low forks Each shoot killed is replaced by multiple ones

14 What Needs Improving (cont.) 4. Adaptability to Variable degrees of degradation Variable natural soil properties Chemistry Microbial communities Variable climates Natural variation across range Future climate change

15 Example of Site Adaptability Local seed 3 yrs Off-site seed source 13.5 Height (ft) Basal stem dia. (in) Crown volume (ft 3 ) Wood biomass (lbs) 2 Scowcroft & Silva. J. Plant Nutrition 28:

16 The Journey to Date 1970s 1973 First published report of genetics research on koa: Isoenzyme variability detected Future direction to examine the extent of variation in koa and look for evidence of adaptation which may be reflected in clinal and ecotypic variation Steiner. Preliminary report on electrophoretic variation in Acacia koa. U.S. IBP Tech Rpt 21.

17 Forest Service funds Dr. Jim Brewbaker to conduct further genetic studies Variation in esterase and peroxidase loci among families Outcrossing indicated as the breeding system, but self-pollination possible Observations indicate genetic differences in tree form superior form on HI island; mostly poor form on other islands Brewbaker Acacia koa project, final report.

18 Clonal propagation studies of koa (R. Skolmen) First step, identify koa plus trees Superior size and stem form 38 individuals found in FR on Hawaii Tree H-15, Humuula FR Skolmen Clonal propagation of Acacia koa. PhD Dissertation, UH Agron & Soil Sci

19 Key findings from early clonal propagation studies: Mist rooting and air layering of root suckers succeeded; grafting failed Successful only when suckers had juvenile foliage Photo by P Pijut Complete plants could also be produced by asceptic culture of shoot tip tissue Concepts proven, but not yet practical for mass propagation Skolmen Clonal propagation of Acacia koa. PhD Dissertation, UH Agron & Soil Sci

20 Vegetatively Propagated 30-yr-old Koa Root-sucker cuttings from superior koa Outplanted at 5000 ft in Laupahoehoe FR Plus-tree traits retained Skolmen Clonal propagation of Acacia koa. PhD Dissertation, UH Agron & Soil Sci

21 Koa Plus-Tree Seed Orchard Established Located at Keanakolu, NE flank Mauna Kea Elevation: 5000 ft Former horse pasture (kikuyugrass) Initial spacing: 6.6 x 6.6 ft Seedlings from 18 parents from E. Hawaii; 2 from Kona Rooted cuttings from 6 parents Skolmen et al In, Brewbaker et al., Improvement of Acacia koa: resource documents.

22 Plus-Tree Seed Orchard Data Shows Genetic Gain Density: (stems/ac): All initially yrs 325 D&C only 210 Crop only 40 Est. 45-yr yield (bf/ac): D&C only 18,330 Crop only 6,510 Vol. shortfall/excess (%): D&C only 92 Crop only 32 Target volume = 9,565 bf/ac Goldstein et al Scowcroft et al. Small-scale For. 9:

23 Most Original Plus Trees Harvested or Suffered Natural Mortality Plus tree H-14 salvaged after dying Gene pool still present in the soil seed bank under the orchard

24 1990s Genetic Improvement Research On Koa Accelerates A 1991 workshop produced Improvement of Acacia koa: Resource Documents, Brewbaker et al. Closely following was Preliminary Evaluation of the Genetic Diversity within the Endemic Hawaiian Acacia koa Complex, Lutzow-Felling et al Common-garden progeny trials established at CTAHR s Hamakua Station and at HARC s Maunawili Station (Brewbaker & Dudley)

25 The 1996 HFIA Symposium: Koa, A Decade of Growth Genetic improvement, a sine qua non for the future of koa, Brewbaker Isozyme studies of genetic variability, Conkle Clonal propagation of Acacia koa, Nagai & Ibrahim Genetic variations of Acacia koa seed, seedling and early growth traits, Sun et al.

26 Field and PhD Dissertation Research Seed source and performance in koa tree establishment, Conrad et al (Common garden study using seed from 4 sites on Hawaii island, 2 on Maui, and 1 each on Oahu and Kauai.) Genetic Improvement of Leucaena and Acacia koa Gray, W. Sun, 1996 Dissertation Genetic variation in morphology and growth characters of Acacia koa in the Hawaiian Islands, Daehler et al. 1999

27 Key Findings from the 1990s Source island affected growth rates and biomass accumulation in common-garden studies in the order of Kauai = Oahu > Maui > Hawaii The genetic variability of koa is large, more so between than within islands As little as 10% of the ~600 koa families evaluated show potential for inclusion in a genetic improvement program

28 2000 to the Present A genetic component to site adaptability Genetic Differentiation of Intrinsic Water- Use Efficiency in the Hawaiian Native Acacia koa, Ares et al UH PhD Dissertation Genetic Improvement of Leucaena Spp. and Acacia koa Gray as High-Value Hardwoods, Xuebo Shi 2003

29 2000 to the Present (cont.) Ploidy Variation in Acacia koa populations, V. Hipkins, Natl. For. Genetics Electrophoresis Lab., 2004 Investigating Koa Wilt and Dieback in Hawaii: Pathogenicity of Fusarium Species on Acacia koa Seedlings, Dudley et al. 2007

30 Key Findings 2000 to Present Extensive progeny trials indicated that bole form, fluting, and limbiness, growth rate, wood properties, resistance to koa wilt (maybe), phyllode and pod shapes, and seed size and arrangement are heritable characteristics

31 Site Adaptability Variation in water-use efficiency across contiguous landscapes is partially under genetic control Such genetic control emphasizes the need for selecting germplasm that is adapted to a given site and avoids genetic contamination of the extant population

32 Principle coordinate and dendrogram analyses of 12 micro-satellite markers confirm the genetic basis of interisland differences in performance in progeny trials Hawaii Maui Oahu Kauai Fredua-Agyeman et al. Genome 51:

33 Vegetative Propagation Photo by SC Nelson Once thought impossible, grafting* and air-layering of material from older trees have now been demonstrated Photo by J DeFrank *Nelson Native Plants:

34 Are We There Yet? Not quite, although progress has been made Landowners can t yet get improved germplasm to support commercial koa forestry Evidence indicates genetic gains will be substantial Establishing a Tropical Hardwood Tree Regeneration and Improvement Center is essential to complete the journey