Freezing tolerance of winter wheat as influenced by extended growth at low temperature and exposure to freeze-thaw cycles

Authors: Skinner, Daniel; Bellinger, Brian

Submitted to: Canadian Journal of Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/23/2016
Publication Date: 9/7/2016
Citation: Skinner, D.Z., Bellinger, B.S. 2016. Freezing tolerance of winter wheat as influenced by extended growth at low temperature and exposure to freeze-thaw cycles. Canadian Journal of Plant Science. doi: 10.1139/CJPS-2016-0154.

Interpretive Summary: Winter wheat is planted in the autumn and harvested the following summer, and therefore must be able to survive the subfreezing temperatures of the winter months. The plants are capable of acclimating to the cold and developing freezing tolerance but they deacclimate too soon and become vulnerable to winter injury long before the spring arrives. In this research, the ability of wheat lines to increase freezing tolerance in response to mild freeze-thaw events was evaluated over 18 weeks of growth at low temperature, as may occur throughout the winter under snow cover. We found that the plants increase freezing tolerance after freeze-thaw events, but only until the plants reach a certain age, and that age varied among the wheat lines studied. This finding provides a new characteristic to examine when evaluating freezing tolerance of wheat plants, and may provide a means to extend the length of time the plants remain freezing tolerant.

Technical Abstract: As the seasons progress, autumn-planted winter wheat plants (Triticum aestivum L.) first gain, then progressively lose freezing tolerance. Exposing the plants to freeze-thaw cycles of -3/3°C results in increased ability to tolerate subsequent freezing to potentially damaging temperatures. This study was conducted to determine to what extent the length of time grown at low temperature influenced the effectiveness of this freeze-thaw enhancement of freezing tolerance. Plants from six winter wheat lines were grown at 4°C for 1-18 weeks, exposed to 0-2 cycles of freezing to -3°C for 24 h, then thawing for 24 h at 3°C, then tested for their ability to tolerate freezing to -10 to -17°C. The freeze-thaw treatments resulted in increased freezing tolerance after 6 to 12 weeks of growth at low temperature, but had no significant effect before or after that time period. Two cycles of -3/3°C freeze-thaw was consistently more effective than one cycle. Variation in the extent and timing of the effectiveness of the freeze-thaw treatments was found among the wheat lines, suggesting genetic variation that may be useful for prolonging freezing tolerance further into the winter months could be found in winter wheat.