Genetic Variation in the Microfibril Angle of Loblolly Pine From Two Test Sites

Abstract

Abstract In recent years, several studies have examined the effect of microfibril angle (MFA) on wood quality. However, little research has been conducted upon the genetic mechanisms controlling MFA. In this study, we examined the heritability of MFA in loblolly pine, Pinus taeda L.,and its genetic relationships with height, diameter, volume, and specific gravity. Increment cores were collected at breast height from 20 to 25 progeny from each of 12 to 17 crosses (among 11 parents) in two modified partial-diallels in different locations in southern Arkansas. Specific gravitywas measured on segments containing rings 1 through 5 and on segments containing rings 6 through 20. MFA was measured on the earlywood and latewood sections of rings 4, 5, 19, and 20. Rings 4 and 5 were chosen as representative of core wood and rings 19 and 20 as representative of outer wood. Analyses of variance revealed statistically significant genetic and environmental influences on MFA. Significant general combining ability (GCA), specific combining ability (SCA), and SCA × block effects indicated that there are both additive and nonadditive genetic influences on MFA. Individual-tree, narrow-sense heritability estimates were variable, ranging from 0.17 for earlywood (ring) 4 MFA to 0.51 for earlywood (ring) 20 MFA. Genetic correlations between MFA, specific gravity, and the growth traits were nonsignificant due to large estimated standard errors. South.J. Appl. For. 28(4):196–204.