• Background
• Goals
• Committee members
• Acknowledgments
• Sponsor Programs
• Literature Cited

Incorporating realized gain from genetic improvement into loblolly pine growth and yield models

Jin Sherry Xiong

Background

 

Forking defects are probably the most serious stem-quality problems in pine trees. Forking defects, including forked stems (Pic. 1) and ramicorn (Pic. 2) or steep-angled branches, may produce large knots and increase difficulty of pruning. It greatly reduces wood yield and wood quality. For tree breeding program, it is important to know about the causes of the forking and the genetic component of it

Stem forking is usually the result of some outside influence and damage, such as insect damage, frost damage or inappropriate silviculture, but forking has a genetic component. Genetic control of forking is necessarily related to the causal the factors for forking. Physiological factors which affect the incidence of forking may be under more direct genetic control.

 

1. Heritability of forking

Franklin and Callanham(1970) found that there is significant difference between families for forking in the study of Lodgepole pine (Pinus contorta var. murrayana Engelm). In addition, Kuser and Knezick(1985) found that forking appeared to be under strong genetic control, with all trees of 10 clones entirely free of forked stems while 50%-100% of tree of 13 others are forked through the clonal plantation of pitch pine. Interestingly, 35 out of 45 trees belonging to Pennsylvania and West Virginia clones are forked at the New Lisbon plantation, while only 1 of 24 trees belonging to Virginia clones has a forked stem. They assumed the forking was a genetic and environmental interaction, or the close spacing increased the forking tendency in the site of Pennsylvania and West Virginia.

In the Ladarch and Lambeth(1991)’s study, forking of Pinus patula, which growing in Colombia, has heritability of 0.46, a rather high value. It predicted the forking of Pinus patula is under genetic control. In red oak(Ouecus rubra), 41% of the seedling from one source were multistemmed while two other sources only had 4% multistemmed seedings(McGee 1968). Genetic parameters of stem forking in 9-year-old Coastal Douglas-fir were estimated by Schermann and Adams(1997) and result showed that the there were significant difference for forking between families. The heritability of ramicorns was 0.43, and heritability of forks was 0.35. Investigation of coastal Douglas-fir by Adams and Bastien(1944) showed that the stem sinuosity had h2 =0.50 and forking had h2=0.44.

Picture 1: A forked stem

 

Picture 2: An example of a ramicorn

 

2. Correlations between forking and other traits.

The Schermann and Adams(1997)’s study showed that both forking defects were positively correlated with stem growth (DBH). Forking defects and stem growth were positively correlated with the second flushing. Genetic correlation between ramicorns and forking was positive, and particularly strong. It indicated that the 2 forking defects are only partially controlled by the same genes (Jarret, 1978).

The correlation analysis failed to show a relationship between seeding height and number of fork per tree in Franklin (1970)’s study of Lodgepole pine, while the average vertical branch angle was significantly negatively correlated with number of forks (r=-0.53). Kerr (2001) found that there was a significant negative relationship between tree height and number of fork at the 14 sites. Significant correlations were revealed between straightness and forking by Savill and Spencer (1999). They also found that forking had a weaker (p=0.014) genotype x environment interaction

Goals

 

In this study, the genetic control of forking and the correlation of forking to growth, stem straightness and other traits will be investigated in 6-year-old diallel tests of loblolly pine, located throughout the Southeast. There are 122 diallel series (12 parents, 30 crosses × 36 trees per cross per site × 4 sites) with sufficient forking (average forking between 20% and 80%) for genetic analysis. A threshold model will be fit to dichotomous data to understand underlying additive and non-additive genetic effects controlling forking in loblolly pine. Results from all 122 diallel series will be presented.

Clonal tests of MeadWestvaco will also be used to assess genetic control of forking. The key advantage of clonal trials for measuring forking is that it converts the trait from a binary trait (any individual tree is either forked or not) to a semi-quantitative trait (of the 10 ramets of a clone at any site, zero to ten can be forked). In addition, DNA markers will be applied to tag the likely position of the genes controlling forking. The identification of quantitative trait loci (QTL) with major effects on forking defects will be accessed, which would increase our understanding of genetic control of this trait. This forking study in elite pedigree will enable us to more successfully breed and deploy non-forked phenotypes.

Committee members

 

Steve McKeand

Email: steve_mckeand@ncsu.edu

Ross Whetten

Email: ross_whetten@ncsu.edu

Fikret Isik

Email: fikret_isik@ncsu.edu

Zhao Bang Zeng

Email: zeng@statgen.ncsu.edu

Acknowledgments

 

I would like to thank my committee members for their guidance. Thanks also to MeadWestvaco and Dave Gerwig for generously allowing access to tests and providing historic data. I’d like to thank all faculty, staff and graduate students in the Tree Improvement Program for their help.

Sponsor Programs

 

NCSU - Cooperative Tree Improvement Program

Literature Cited

 

Adams,W. T. and Bastien. J. C. 1994. Genetics of second flushing in a French population of coastal Douglas-fir. Silvae Genetica 43: 344–351.

Franklin, E.C. and Callaham, R.Z. 1970. Multinodality, branching, and forking in Lodgepole pine (Pinus contorta var. murrayana Engelm.). Silvae Genet.19:180-184.

Falconer, D.S. 1989. Introduction to quantitative genetics. Longman Scientific and Technical, Essex, Enland.438.

Gary Kerr and Roger C. Boswell. 2001. The influence of spring frosts, ash bud moth(Prays fraxinella) and site factors on forking of young ash (Fraxinus excelsior) in southern Britain. Forestry 74(1) :29-40

Kuser, J.E. and D.R. Knezick. 1985. Twenty-year observations on a clonal plantation of pitch pine in the New Jersey Pinelands. Bulletin of the Torrey Botanical Club.112: 318-323.

Ladrach, W.E. and Lambeth, C. 1991.Growth and heritability estimates for a seven-year-old open-pollinated Pinus patula progeny test in Columbia. Silvae Genet.40:169-173.

Li, P. and Adams, W. T.1993.Genetic control of bud phenology in pole-size trees and seedlings of coastal Douglas-fir. Can. J. For. Res. 23: 1043–1051.

Namkoong, G. 1979. Introduction to quantitative genetics in forestry. USDA For. Serv. Tech. Bull. No.1588, 342 p.

Rudolph, T.D.1964. Lammas growth and prolepsis in jack pine in the Lake States. Forest Sci. Monogr.6:1-70.

Savidge, R.A., J.R. Barnett and R.Napier. 2000. Cell and molecular biology of wood formation. Bios Scintific publishers limited.389-391.

Schermann, N, W.T. Adams, S.N. Aitken, J.-CH. Bastien. 1997. Genetic parameters of stem form traits in a 9-year-old coastal Douglas-fir progeny test in Washington. Silvae Genetica 46:2–3.