Adequate winter hardiness has always been the corner stone for the adaptation of perennial crops for cultivation in Northern latitude. Peculiar light conditions and extremely long winter create special over-wintering conditions. Genotypes of Northern origin have adapted to these conditions by early growth cessation is autumn to ensure long cold acclimation period. Climate change has already extended the growing period in Finland and the management of forage grasses has been adapted to new growing conditions. Typically it means change from two to three cuts in intensively managed forage leys and thus, more effective use of the entire growing period. However, the extended fall growth and later growth cessation is negatively correlated with winter hardiness. What kind of forage grass or forage legume cultivars we should have in the future? How much genetic variation exists in traits related to winter survival that could be utilized in the future? And how vernalization requirement is related to winter survival? Field experiments on different forage grass species (P. pretense, Festuca pratensis and Lolium perenne) as well as in alfalfa revealed that during ‘normal’ winter the minimum freezing tolerance was reached in December-January, after which it was gradually lost. Surprisingly two of the studied four years were ‘abnormal’ and even the most winter hardy genotypes did not develop freezing tolerance. During those years the plants were particularly vulnerable for winter damage during spring when the protected snow cover melted. Hand in hand with the decrease of freezing tolerance, vernalization saturation was reached. Both our field and growth chamber experiments supported the observation that the extremely long winter in Finland results can decrease yield potential in forage grasses. It seems that the yield potential was the highest once the vernalization requirement was fulfilled in January-February. During our studies on the day length and temperature regulation of vernalization and growth cessation we learned that there is a great variation between the studied species. The growth of northern timothy genotypes were regulated strongly by day length whereas Festuca, Lolium, alfalfa as well as Southern timothy genotypes responded to temperature. We are currently exploring how this interesting variation between species could be utilized in management and what is the molecular and genetic basis of this variation.
Seppänen, M. M., Jokela V., Korhonen P., Isolahti M., Virkajärvi, P. 2016. Development of vernalization and its effects on freezing tolerance and canopy structure in forage grasses. (submitted to Forage and Grassland Science)
Jokela V., Uusitalo, T. Seppänen M. 2016. Temperature, day length and genotypic regulation of autumn growth in timothy, perennial ryegrass and Festulolium accessions. (manuscript)
Østrem L, Helgadóttir Á, Niemeläinen O, Seppänen M, Greve Pedersen M, Halling M, Rognli OA 2015. Environmental impact on winter survial and production in non-native grasses in the Nordic countries. In: Zeverte-Rivza S (editor) Proceedings of the 25th NJF Congress, Nordic View to Sustainable Rural Development, Riga, Latvia 16-18 June 2015, pp. 127-133 (ISBN 978-9934-14-548-3).
Panu Korhonen 2014. Development of freezing tolerance and vernalisation in forage grasses in field experiments (2009–2013), MSc thesis 63 p.
Tiina Toivonen 2014. Autumn growth of forage grasses – differences between forage cultivars. MSc thesis, 70 p.
Luhtanen, J. 2011. Cold tolerance, vernalisation requirement, growth and development of timothy (Phleum pratense ssp. pratense L.) and the effect of the species origin on these factors. MSc thesis, 75 p.
Alitalo, V. Freezing tolerance and winter survival of six alfalfa (Medigago sativa L.) cultivars with special reference on carbohydrate metabolism. MSc thesis under preparation.