Natural variation in autumn senescence in Swedish Aspen (Populus tremula).

LUQUEZ VIRGINIA; FRACHEBOUD YVAN; JANSSON STEFAN

Salzau, Alemania

Workshop; Third European Workshop on Plant Senescence; 2007

SenNet (European Network on Plant Senescence)

Natural variation in autumn senescence in Swedish aspen (Populus tremula)   Virginia M. C. Luquez *, Yvan Fracheboud, Stefan Jansson. Umeå Plant Science Centre, Umeå University, Umeå, Sweden. * Present address: Instituto de Fisiología Vegetal, La Plata, Argentina. virginia.luquez@plantphys.umu.se   The natural variation in autumn leaf senescence was analyzed in a set of aspen trees collected in 12 sites in Sweden, from 55 to 66 º of latitude; this group of trees is known as the Swedish Aspen Collection (SwAsp, Ingvarsson et al 2006). The trees were grown in pots in a greenhouse with the natural irradiance and photoperiod of the area of Umeå during the year 2006. During the autumn, we measured the date of start and the rate of autumn senescence in the SwAsp. The date of start of autumn senescence showed a clear clinal pattern along latitude: the populations from northern Sweden were the first to senesce and the southernmost populations were the last ones to senesce, with a difference of 25 days between them. The latitude of origin of the populations explained most part of the variation in the start of senescence (R2= 0.95), suggesting that there is an adaptation to the local environmental conditions. On the other hand, the rate of senescence did not show any clear pattern of variation along latitude. We also explored the relationship between bud set and autumn senescence. The correlation between the start of senescence and bud set was positive and highly significant (r=0.647, p<0.0001), implying that the trees that set buds late in the season also had a late start of senescence, and suggesting that both are controlled by the same environmental signal. Bud set is induced by the reduction of photoperiod (Ingvarsson et al 2006), and the results obtained here suggests that this is also the case for the start of autumn senescence.   References Ingvarsson PK, Garcia MV, Hall D, Luquez V, Jansson S (2006) 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). Genetics 172: 1845-1853.