Abstract A study of spiral grain on material from 52 control-pollinated families of 4-year-old loblolly pine ( Pinus taeda ) indicated that genetic variation in this trait is of the nonadditive type. The study involved 1,043 trees, and spirality was measured in that portion of juvenile wood where spirality often attains maximum values. Results suggest that mass selection to reduce spiral grain will not be very effective if the pattern for older trees is similar to that of the young trees studied. Spirality bad enough to cause serious degrade in sawn or veneer products rarely occurred; this raises some question as to whether spiral grain in loblolly pine is a serious problem. The reference or datum from which degree of spirality is determined is important; since spirality was measured as deviation from pith in this study, results must be interpreted in this light.
Zobel et al. (Sun,) studied this question.
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