Genetics of Stem Forking and Ramicorn Branches in a Cloned Loblolly Pine Family
Forking defects and ramicorn branching were assessed in a cloned full-sib family of loblolly pine (Pinus taeda L.). The proportion of forking ranged from 13 to 21% across four test sites with a mean of 17%. Ramicorn branching incidence averaged 24% and varied from 18 to 31% over all sites. There were significant differences among clones within this family for all traits studied. The estimated clone mean repeatabilities were moderately high for forking defects (0.67‐0.86). Through single trait selection with a selection differential of 4%, the proportion of trees with forks and ramicorn branches could be reduced 10 and 13%, respectively. Low to moderate unfavorable genetic correlations were found between growth traits and forking defects (0.12‐0.45), suggesting that selection for either trait alone will negatively affect the genetic response for the other. No significant environmental correlations were found between forking and growth. A moderate significant positive genetic correlation between stem forking and ramicorn branching indicates that both traits may be partially controlled by the same genes and could be improved simultaneously. Strategies are discussed for within-family selection to capture more gain for increased growth and reduced stem forking for the breeding of loblolly pine.
No Supplementary Data
No Article Media