The variation of timing of terminal bud set and frost hardening in first-year seedlings of Scots pine (Pinus sylvestris is L.) was studied. Both bud set and frost hardiness showed clinal variation with respect to latitude over a steep environmental gradient (60-67 degrees N) in Finland. Northern populations set buds and developed frost hardiness earlier than southern populations. Backcrosses ((north x south) x south) were intermediate or close to the southern parent both in bud set and in frost hardiness between the populations representing the parental origins. In bud set, 36.4% of the total variation was between the populations. The bud set date and development of frost hardiness were highly correlated at the population level (r = 0.69-0.97). Frost hardening started during the bud formation period and accelerated A hen most of the buds had formed. In backcross progenies, earlier bud set resulted also in earlier development of frost hardiness. This suggests a genetical association between the two traits.
Hurme, P; Repo, T; Savolainen, O; Paakkonen, T
Climatic adaptation of bud set and frost hardiness in Scots pine (Pinus sylvestris)
Canadian Journal Of Forest Research