Genetic variation in characters of importance for stand establishment in Sitka spruce (Picea sitchensis (BONG) Carr.)

This paper summarizes the results of 2 series of clonal trials-F206 including 151 clones and F215 including 196 clones. The characters measured are: selection intensity for height growth in the nursery, height, autumn coloration, flushing, leader breaks, April-frost damage, and mortality, all characters of expected importance for stand establishment. Genotype-environment interaction and correlation between characters are studied as well. Compared to the standard, a direct import from Queen Charlotte Islands, the clones, selected in a danish second generation material, have a superiority in height growth of 23% to 31%, fewer leader damage, 16% to 17%, and less damage due to April-frost, score 1.1 to 2.5, whereas there is hardly no differences in flushing time and only minor differences in mortality, 1% to 5% less dead trees. There is considerable variance among clones for April-frost damage, but the results are only based on one year. If the frost hits later in the spring the differences between the clones will probably be less because they all are closer to the growing season and all will have an active cambium. Severe damage due to April-frost is a rather seldom event in Denmark. and one may question the effort to avoid damage by selecting less sensitive clones, unless it is an indirect gain by selecting for late flushing clones to late spring frost exposed sites, where even small differences in time of flashing will make a difference. There is only a very limited possibility to select for late flushing in spite of high heritability estimates. Autumn coloration shows no reasonable correlations to held damage and may not be an appropriate measure of autumn hardening. Selection based on 3 year old cuttings yield about 63% to 77% of the results obtained by direct selection 5 years later in the field. Concerning the ageing-problem of the hedges for cutting production 3 year nursery results seem to be a reasonable basis to start commercial production of selected clones. Early selection of ortets among 3 or 4 year old seedlings for height growth seems not to be an appropriate way to increase height growth within the danish provenance. General problems with ageing of propagation material restricts the practical use of the clonal material. Clonal mean values of ecovalence as a stability measure is estimated for the characters showing genotype-environment interaction. Only a rather Limited number, around 15%, of the clones acounts for more than 50% of the genotype- environment interaction sums of square.