Heritability and type B genetic correlation estimates for coastal douglas-fir in the US Pacific Northwest: trends and insights from 906 first-generation and second-cycle tests

Abstract

ABSTRACT Genetic parameters are reported for coastal Douglas-fir, from measurements on 24,000 first-generation open-pollinated families (786 test sites) and 2,400 second-cycle crosses (120 test sites) over a period of 45 years. The following were estimated: across-site narrow-sense individual heritability (h2 A), narrow-sense family mean heritability (h2 F), and type B genetic correlation (rB), and. narrow-sense single-site heritability (h2 w). The main traits were height, diameter at breast height (dbh), volume index (both cycles), and incidence of stem forking and ramicorn branching, upper stem sinuosity, and second flushing in the leader (second cycle). Smaller datasets were available for progression of budburst, straightness, needle retention, wood specific gravity and acoustic velocity. Measurements were between three and 30 years from planting. The dataset contained at least one trait measured for 2.602 million trees . Heritability (h2 A) estimates for height, dbh, volume and sinuosity ranged from 0.15 to 0.30, with a wider range for h2 w estimates. Heritabilities were higher in the second cycle. Forking and ramicorn branching had good h2 F heritabilities. Second flushing had high h2 A and rB values; the same is often true for AV. Budburst was the most strongly inherited trait. h2 w for height, dbh, volume, forking and ramicorns was correlated with means for those traits.