GENETIC-PARAMETERS IN DIALLEL-CROSSED SCOTS PINE FAVOR HEARTWOOD FORMATION BREEDING OBJECTIVES

After 25 years, full-sibs of Scots pine (Pinus sylvestris L.) in a nor th Swedish progeny test showed an estimated heritability of 0.30 for h eartwood diameter at 80 cm above ground. This was equal to the heritab ility estimate for tree height, although accompanied by a much larger additive genetic coefficient of variation (0.20 compared with 0.06). T he heritability estimate for diameter at breast height was about half that for tree height. Strong and positive phenotypic and environmental correlations were assessed between heartwood and the following traits : diameter at breast height, tree height, and branch diameter. The gen etic correlation was low and positive at 0.02 between heartwood and di ameter at breast height in contrast with 0.27 between heartwood and tr ee height. The assessed genetic correlations between heartwood and bra nch diameter and between heartwood and crown length were very weak com pared with the phenotypic and, particularly, environmental correlation s. This indicates that the association between crown length and heartw ood is significant with regard to environmental factors, no matter to what extent they are independently modified by genes. However, crown l imit was the trait that showed the strongest genetic correlation with heartwood (0.49). Since no correlations with production traits were un favorable, we conclude that including heartwood formation capacity in a breeding program may be done without drawbacks and with good prospec ts for success.