Heritability of first and second-year height growth of Pinus sylvestris (L.) plants was studied using three different mating designs. Plants grew in a plastic greenhouse during the first growth period. During the second growth period they were exposed to open air conditions.
Heritability values varied from zero to 42%. An average heritability based on six separate calculations (two from each mating design) was computed and its reliability was discussed. This heritability value was 18%.
Different ways of improving heritability estimates was discussed and the need of more investigations on trait quality in relation to fitness and on the effect of natural selection and population strategy was emphasized.