Clinal variation in phyB2, a candidate gene for day – length induced growth cessation and bud set, across a latitudinal gradient in European aspen (Populus tremula).

INGVARSSON P, GARCÍA V, HALL D, LUQUEZ V, JANSSON S.

GENETICS

Año: 2006 vol. 172 p. 1845 - 1853

0016-6731

Abstract. The initiation of growth cessation and dormancy represents a critical ecological and evolutionary trade-off between survival and growth in most forest trees. The most important environmental cue regulating the initiation of dormancy is a shortening of the photoperiod and phytochrome genes have been implicated in short-days induced bud set and growth cessation in Populus. We characterized patterns of DNA sequence variation at the putative candidate gene phyB2 in four populations of European aspen (Populus tremula) and scored single nucleotide polymorphisms in an additional twelve populations collected along a latitudinal gradient in Sweden. We also measured bud set from a subset of these trees in a growth chamber experiment. Bud set showed significant clinal variation with latitude explaining approximately 90 % of the population variation in bud set. A sliding window scan of phyB2 identified six putative regions with enhanced population differentiation and four SNPs showed significant clinal variation. The clinal variation at individual SNPs is suggestive of an adaptive response in phyB2 to local photoperiodic conditions. Three of four SNPs showing clinal variation were located in a region with excessive genetic differentiation, demonstrating that searching for regions of high genetic differentiation can be useful for identifying sites putatively involved in local adaptation.