Christmas Tree Genetics Program
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The Christmas Tree Genetics Program at NC State University focuses on tree improvement strategies for species that are particularly important to North Carolina's Christmas tree industry. Each of tree improvement program is uniquely tailored to the individual species according to their biologic constraints and importance to the state's industry.
- Fraser Fir
- Virginia Pine
- Eastern White Pine
- Eastern Redcedar
- Leyland Cypress
Virginia Pine
Introduction
Virginia pine (Pinus virginiana Mill.) is the second most commonly planted tree species for Christmas tree production in North Carolina. Visit the National Christmas Tree Association Web site for a description of Virginia pine. It is widely planted by North Carolina Christmas tree growers east of the Appalachian Mountains where Fraser fir (Abies fraseri (Pursh) Poir.) cannot be successfully grown. Virginia pine is a deserving Christmas tree species because of its:
- rapid growth (3 to 5 years to harvest)
- short needles
- good branch structure for holding ornaments
- pleasant pine scent
- dark green color
However, Virginia pine also has several significant problems as a Christmas tree species. Chief among these problems are
- poor stem form,
- non-uniformity
- extreme susceptibility to damage by the Nantucket pine tip moth (Rhyacionia frustrana (Comstock)).
In fact, due to the cumulative effect of these and other problems, growers typically only market about 50% or less of Virginia pines planted. The future use of genetically improved planting stock will help improve this yield.
Currently, the planting stock of most North Carolina growers originates from the North Carolina Division of Forest Resources’ seed orchard at the Morganton Forestry Research Center. This orchard contains 20 clones that were selected for forest production rather than for Christmas tree production. While this material is a good temporary source for growers, a comprehensive comparison of available Virginia pine material is needed. The intensive effort and resulting high value in growing Christmas trees (relative to forest products) warrants identification and use of the best available material by growers.
Tree Improvement Program
The tree improvement strategy includes establishment of the Virginia Progeny Test Series using open-pollinated seeds from select trees of existing forest tree improvement programs. These selections were originally made based on growth and stem form. The current progeny test series will be shared and managed as Christmas trees and additional traits such as branching habit and tip moth resistance will be evaluated. As good performing families are identified in these tests, recommendations made so that growers can obtain good quality seed form existing seed orchards. Eventually, elite selections will be made from these tests and grafted into a control-pollinated seed orchard to provide growers will genetically improved seed. The following table shows the anticipated schedule for the Virginia pine tree improvement program.
| Date(s) | Activity(ies) |
| 1997-1998 | Collected & stratified seed for progeny tests Sowed seed and cultured seedlings in greenhouse Established the Virginia Pine Progeny Test Series |
| 1998-2001 | Culture & measure tests |
| 2000 | Plant rootstock for control-pollinated seed orchard |
| 2001 | Graft selections for control-pollinated seed orchard Make recommendations for best families from other existing seed orchards |
| 2005 | Orchard seed is expected to meet planting demand |
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Eastern Redcedar
Introduction
Eastern redcedar (Juniperous virginia L.) is a traditional Christmas tree species commonly planted in North Carolina. Visit the National Christmas Tree Association Web site for a further description of Eastern redcedar. This species makes an ideal candidate for clonal Christmas tree production. Unlike pine species, eastern redcedar roots readily at the ages of concern for Christmas tree production. Further, maturation effects on the growth and development of rooted cuttings appear to be negligible. Many cultivars (clones) of eastern redcedar exhibiting a wide variety of growth habits and colors have been propagated in the horticultural industry for years. Although eastern redcedar is an important Christmas tree species, the relatively small number of trees planted each year makes it difficult to justify a large-scale breeding program for this species. However, clonal screenings within the currently used planting stock can serve to provide growers with uniform and superior planting stock for the near future. Later, if new clonal material is desired, screening of other sources of redcedar or of hybrids with other Juniperus species may be undertaken.
Clonal Testing
Christmas tree plantations of seven interested growers (Table 1) were searched for select trees early in 1997. Thiry-two individual tree selections were made. Measurements were taken for each selection and 5 surrounding check trees.
| Grower | County |
# Selections |
| Snodie Wilson | Pitt | 4 |
| David Corn | Granville | 4 |
| Eric Cobb | Guilford Prince William (VA) |
7 |
| Jack Rich | Edgecombe | 2 |
| Dorsey Daniel | Harnett | 3 |
| Dan McInnis | Johnston | 5 |
| Whit Jones | Duplin | 2 |
| Total |
32 |
|
| Table 1. Grower and location (county) of North Carolina Eastern redcedar selections. | ||
Trees which are outstanding in any of the following four categories were candidates for the clonal testing program: 1) growth and form, 2) color, 3) foliage softness, or 4) resistance to Phomopsis blight. Selection criteria for each of the four traits of interest are outlined in Table 2.
One selection criteria was apparent resistance to Phomopsis blight. This disease of eastern redcedar is caused by the fungus Phomopsis juniperovora Hahn. Its primary symptom is browning and death of branches. This browning usually begins on branch tips and progresses toward the stem of the tree. The fungus can completely kill seedlings and small trees by infecting the stem and girdling it with dead tissue. Although its extent is not currently known, several growers are having severe problems with this disease in their Christmas tree plantations. To be effective, selection of disease-free trees must occur in plantation with a high incidence of the disease.
| Selection Trait |
Criteria |
| Growth & Form | -- exceeds or equals height of the 30 nearest trees |
| Foliage Color | -- pleasing color either before or after artificial coloring |
| Foliage Softness | -- less than 5% of foliage is of juvenile (prickly) type |
| Resistance to Phomopsis Blight | -- pest-free |
| Table 2. Selection criteria for four traits of interest in the North Carolina eastern redcedar clonal program. | |
The selections were rooted in a propagation greenhouse at the NCSU Horticultural Field Laboratory during 1997. Average rooting percent was 66% with individual clones ranging from 16 to 98%.
In early summer of 1998, these rooted cuttings were potted into larger containers for outdoor culture. In the future, multiple copies of each clone will be represented in each of three clonal tests. These tests will be measured annually. Rooted cuttings of all clones will be archived in a clone bank. A protocol will be developed for making cutting material available to North Carolina growers and nursery producers interested in developing hedge orchards of the most promising clones for their own rooted cutting production. A proposed schedule of activites for the Eastern redcedar clonal propagation program is presented in Table 3.
|
Date |
Activity |
1997 |
Selected 32 trees in Christmas tree plantations Rooted 100+ cuttings / selection |
1998 |
Transplanted rooted cuttings into pots Cultured cuttings outdoors |
1999 |
Root cuttings for clonal archive Establish clonal field trials 1st year field measurements |
2000 |
Start production hedge orchard 2nd year field measurements |
2001 |
Continue hedge orchard development 3rd year field measurements |
| Table 3. Proposed schedule for Eastern redcedar clonal propagation program. | |
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