Gain efficiency in short-term testing: experimental results

Abstract

Height growth of loblolly pine (Pinustaeda L.) was measured in trees subjected to one of five irrigation and fertilization regimes in a closely spaced genetic test for 3 years. Shoot components of 3rd-year annual height increment were measured over two contrasting treatments. Juvenile height and number of stem units in summer growth length in the fully irrigated and fertilized short-term test regime exhibited (i) the highest juvenile-mature correlations (family mean correlation = 0.41–0.68), (ii) high individual-tree heritabilities (0.38–0.44), which were two- to three-fold higher than older tree values in a conventional genetic test of the same families, (iii) high genetic stability across two extreme short-term test treatments (genetic correlation = 0.61–0.80), and (iv) an efficiency in genetic gain per generation of 81–87% relative to selection on height at age 8 years.