Variation in the rate of winter hardening of one-year-old plus-tree families of Scots pine raised in different enviroments.

Abstract

The effect of different environmental conditions (four outdoor localities and one greenhouse locality in Northern Sweden) on cold hardening of 29 one-year-old full-sib families from plus-trees of Scots pine ( L.) were studied by artificial freeze testing. Plants exposed to low night temperatures during August achieved faster cold hardening than plants raised in milder localities. The family ranking for rate of winter hardening was consistent among outdoor localities if freeze testing was performed at times when plants from different localities had attained similar levels of cold hardiness. However, significant family x locality interactions were obtained when plants from the outdoor localities were freeze tested on the same occasion. Freeze damage was positively correlated with plant height but not correlated with dry matter content in the autumn. Freezing damage of greenhouse raised plus-tree families was uncorrelated with damage of plants raised outdoors. Possible implications for hardiness breeding are suggested.Pinus sylvestris