JXB Advance Access originally published online on May 12, 2009
Journal of Experimental Botany 2009 60(11):3143-3155; doi:10.1093/jxb/erp142
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RESEARCH PAPER |
Evolutionary change in flowering phenology in the iteroparous herb Beta vulgaris ssp. maritima: a search for the underlying mechanisms
Laboratoire Génétique et Evolution des Populations Végétales, UMR 8016, CNRS, Université Lille 1, F-59655 Villeneuve d'Ascq, France
* E-mail: henk.van-dijk{at}univ-lille1.fr
The potential for evolutionary change in flowering time has gained considerable attention in view of the current global climate change. To explore this potential and its underlying mechanisms in the iteroparous perennial Beta vulgaris ssp. maritima (sea beet), artificial selection for earlier and later flowering date was applied under semi-natural greenhouse conditions. Mean flowering date occurred more than 30 d earlier in 13 generations in the early selection line, but response was weaker in the late selection line. Taking advantage of the growing knowledge on the genetics and the physiology of flowering induction, particularly in Arabidopsis thaliana, the results obtained here were analysed in terms of the four different pathways of flowering induction known in this species. A first significant correlated response was stem elongation (bolting) in the vegetative stage, suggesting that plants were thus able to flower earlier as long as other requirements were satisfied. Vernalization had a clear influence on flowering date and its influence increased during the selection process, together with sensitivity to photoperiod. Vernalization and photoperiod could compensate for each other: each additional week of vernalization at 5 °C decreased the necessary daylength for flowering by about 15 min during the later selection stages, while in unselected plants, it was about 7 min. Devernalizing effects were observed at short days combined with higher temperatures. Special attention was given to the role of the B (bolting) gene that cancels the vernalization requirement. The results here obtained suggest that all four known pathways may simultaneously participate in evolutionary change.
Key words: Artificial selection, Beta vulgaris ssp. maritima (sea beet), correlated response, flowering time, heritability, perennial, photoperiod, stem elongation, vernalization
Received 17 February 2009; Revised 7 April 2009 Accepted 9 April 2009