Physiological basis of the disturbances in frost tolerance of winter oilseed rape as a result of deaclimation processes – role of brassinosteroids

Oilseed rape (Brassica napus L.) is one of the main oil plants that are cultivated in the world.
In the EU, Poland is one of the leading producers of oilseed rape. An increase in the world
production of oilseed rape occurred after a drastic reduction or even elimination of erucic acid in the
process of breeding as well as a significant decrease in the glucosinolate content. This made oilseed
rape oil a high-quality fat and a source of valuable feed. The yield of winter oilseed rape is higher
than the yield of spring oilseed rape, but part of its growing season is during the winter months,
which is connected with the exposure of the plants to frost. Well cold acclimated (during autumn)
oilseed rape plants are able to easily survive frost, especially under snow cover. However, the
problem of recent years is the occurrence during autumn (or early spring) short periods with
abnormally elevated temperatures. It results from climate changes and disturbs the natural process
of preparing plant metabolism to survive frost (reducing plant frost tolerance). The phenomenon is
called deaclimation of plants. As a result of the decreased frost tolerance farmers in Poland are
forced to plow entire winter oilseed rape plantations injured during the winter. In experiments
planned in proposed project we are going to determine which of the oilseed rape cultivars have
high frost tolerance despite the occurrence of decalimation (which cultivars have a higher
decalimation tolerance). We will also look deeper into specific physiological and biochemical
changes that occur during the deaclimation process, such as changes in the hormonal homeostasis,
changes in the properties of cell membranes (chloroplast membranes) and the dynamics of changes
in protective proteins or selected elements of the antioxidant system. It will enrich the current
knowledge in the field of deaclimation research. The implementation of the project will also answer
the question whether the use of plant steroid hormones - brasinosteroids, increases oilseed rape
tolerance to frost after periods of deaclimation. Determining that the frost tolerance of oilseed rape
is improved by brassinosteroids may open the way for the use of these compounds for spraying the
plants in agricultural practice, especially in regions where the largest frost injuries of this species
are associated with deaclimation processes.