Early selection efficiency for fiber dimensions and their relationships with growth and wood quality for Pinus elliottii Engelm. in southern China

A solid understanding of the efficiency of early selection for fiber dimensions is a prerequisite for breeding slash pine (Pinus elliottii Engelm.) with improved properties for pulp and paper products. Genetic correlations between size of fibers, wood quality and growth properties are also important. To accomplish effective early selection for size of fibers and evaluate the impact for wood quality traits and ring widths, core samples were collected from 360 trees of 20 open-pollinated Pinus elliottii families from three genetic trials. Cores were measured by SilviScan, and the age trends for phenotypic values, heritability, early-late genetic correlations, and early selection efficiency for fiber dimensions, such as tangential and radial fiber widths, fiber wall thickness and fiber coarseness, and their correlations with microfibril angle (MFA), modulus of elasticity (MOE), wood density and ring width were investigated. Different phenotypic trends were found for tangential and radial fiber widths while fiber coarseness and wall thickness curves were similar. Age trends of heritability based on area-weighted fiber dimensions were different. Low to moderate heritability from pith to bark (similar to 0.5) was found for all fiber dimension across the three sites except for tangential fiber width and wall thickness at the Ganzhou site. Early-late genetic correlations were 0.9 after age of 9 years, and early selection for fiber dimensions could be effective due to strong genetic correlations. Our results showed moderate to strong positive genetic correlations for modulus of elasticity and density with fiber dimensions. The effects on fiber dimensions were weak or moderate when ring width or wood quality traits were selected alone. Estimates of efficiency for early selection indicated that the optimal age for radial fiber width and fiber coarseness was 6-7 years, while for tangential fiber width and wall thickness was 9-10 years.