Study of Freezing Tolerance After Cold Acclimation Followed by Deacclimation in Winter and Spring Canola (Brassica napus L.)

Winter canola/rapeseed (Brassica napus L.) produced 20 to 30% greater yield over spring canola. It overwinters to flower in spring. The winter type shows increased freezing tolerance after cold acclimation, which is crucial to survive in winter. However, short duration warm spells can cause canola to lose increased freezing tolerance in a process called ?deacclimation? making it again vulnerable to freezing damage. We found canola almost completely deacclimated at 13?C or more for at least two days of deacclimation. However, longer duration of deacclimation (7 & 14 days) showed increased freezing tolerance as compared to 2 & 3 days at 10?C or less. Variation was seen among winter varieties for deacclimation seems unrelated to cold acclimation ability. Previous genome wide association studies implicated VERNALIZATION INDEPENDENCE 3 (VIP3) as having a potential role in deacclimation. We demonstrated that mutations in VIP3 makes Arabidopsis more tolerant to deacclimation. Deacclimation resistant and susceptible varieties could be used for further study to better understand deacclimation on genetic and physiological level