Scaling of estimated breeding values for stand productivity in the Australian Pinus radiata breeding program

Abstract

ABSTRACT The radiata pine tree improvement program in Australia estimates breeding values for selection criteria traits (SCTs) such as diameter at breast height and height, as measured in progeny trials. The data in each trial are standardised so that estimated breeding values (EBVs) are expressed in units of additive genetic standard deviations. EBVs for harvest-age breeding objective traits (BOTs), such as stand volume mean annual increment (VMAI), are predicted from the SCT EBVs and expressed in measurement units. BOTs are not routinely measured in progeny trials because it would prolong the generation interval. However, the slope of the relationship between VMAI and BOT EBV provides an estimate of the scale of VMAI EBVs. This slope was estimated using 26 block-plot realised-gain trials with stand total produced basal area (TPBA) measurements near age ten years and 11 trials with final VMAI measurements between 15 and 25 years extrapolated to a harvest age of 25. In all trials, EBVs were positively correlated with growth, demonstrating substantial realised genetic gains. At age ten years, on average, one standard deviation of BOT EBV corresponded to a realised gain in TPBA of 3.7 m2 ha−1 and an additive coefficient of variation (CVA) of 11.2%. At the harvest age of 25 years, one standard deviation in EBV corresponded on average to realised gains in VMAI of 4.2 m3 ha−1 y−1 and a CVA of 15.0%. Methods for incorporating estimated genetic gains into growth and yield modelling and forest valuations are discussed.