High heritability for heartwood in north Swedish Scots pine

In 44-year-old full-sibs of north Swedish Scots pine (Pinus sylvestris L.), the estimated heritability of heartwood diameter was 0.5 despite the influ ence of environmental changes (caused by an earlier thinning) which apparen tly had reduced the heritabilities of height and diameter to around zero. T he heritability of bole straightness was estimated to be 0.6. The coefficie nt of additive genetic variation of heartwood diameter was estimated at 0.2 , Lf a reliable 'heartwood-meter' becomes available that allows nondestruct ive measurements to be rapidly made in the field it should be possible to b reed for or against heartwood formation with less effort compared with that required in breeding aimed at improving regular production traits.