Efficiency of early selection for growth and wood quality traits of slash pine in three progeny trials in southern China

A firm understanding of the early selection efficiency of ring width and wood quality traits is a prerequisite for breeding of higher growth rates and wood quality of slash pine (Pinus elliottii Engelm.). To accomplish effective early selection for the studied traits, wood core samples were collected from 360 trees of 20 open-pollinated families from three slash pine rotation-aged (harvest age) genetic trials. Wood cores were measured by SilviScan, and the annual patterning, heritability, age-age genetic correlation and efficiency of early selection for ring width, modulus of elasticity (MOE), microfibril angle (MFA) and wood density for early to reference age (age 27) were investigated. The greatest annual ring width was observed at age 4, and this trait decreased gradually toward the bark. Different radial trends were found for MOE and MFA. Wood density was lowest near the pith and then increased steadily with age. Overall, heritability was moderate to high for all area-weighted wood quality traits. Very high age-age genetic correlation values were observed for all traits researched. Estimates of efficiency for early selection indicated that the optimal age of early selection for ring width was 9-12 years, while that for area-weighted MOE, MFA and wood density was 7-8 years.