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

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 (h(2) (A)), narrow-sense family mean heritability (h(2) (F)), and type B genetic correlation (r(B)), and(.) narrow-sense single-site heritability (h(2) (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 (h(2) (A)) estimates for height, dbh, volume and sinuosity ranged from 0.15 to 0.30, with a wider range for h(2) (w) estimates. Heritabilities were higher in the second cycle. Forking and ramicorn branching had good h(2) (F) heritabilities. Second flushing had high h(2) (A) and r(B) values; the same is often true for AV. Budburst was the most strongly inherited trait. h(2) (w) for height, dbh, volume, forking and ramicorns was correlated with means for those traits.

Automated summary

Genetic parameters of coastal Douglas-fir were studied over a period of 45 years, revealing variations in heritability for traits like height, diameter, and volume, with higher heritabilities in the second generation. Traits like stem forking and branching exhibited good heritabilities, while second flushing had high genetic values. The findings provide important insights for the selection and improvement of genetic traits in forestry.