Data from: Freezing damage in canola (<i>Brassica napus</i> L.) shows varietal differences for deacclimation rates and temperature thresholds for deacclimation initiation

<p dir="ltr">These data indicate the raw freezing survival scores (0=dead, 3=undamaged) of canola that was acclimated for 4 weeks at 5C and then deacclimated at the indicated times and temperatures and then frozen for 4 hours at -13C- followed by recovery for 7 days prior to scoring. The data is shown for 6 replicates for each line with the first column indicating the genotype, the number of days (column 2) at each temperature (column 3), the replicate number (column 4) the experimental run 1 or 2 (column 5) and the survival score (column 6).</p><p dir="ltr">Nine varieties of winter type canola with divergent freezing tolerances following cold acclimation (Chao et al., 2021) and deacclimation (Horvath et al., 2020b) were chosen from a diversity panel used to conduct genome wide association studies on freezing tolerance and deacclimation resistance (Horvath et al., 2020a). Two spring type canola (<i>Wester </i>and <i>Regina II</i>) were also used as controls. Experiments were conducted using a randomized complete block design (RCBD) with six replicates and a single plant as an experimental unit. Each experimental unit was performed two times and data for each independent experiment is presented (see: experiment I and experiment II in the results). Plants were grown in 800mL pots and potting soil (Promix from PREMIER HORTICULTURE INC) under greenhouse conditions for 4 weeks (6-8 leaf stage) at ~22°C. The photoperiod was 16 h of light with supplemental halogen lighting as needed. Plants were fertilized with 20-20-20 NPK mixed fertilizer once a week in a greenhouse and plants were watered as needed (Horvath et al., 2020a).</p><p dir="ltr">After 4 weeks of growth under the greenhouse conditions, plants had reached the 6 to 8 leaf stage and were moved to a cold acclimation chamber at 4-5°C with 12-h photoperiod (with supplemental full spectrum LED lighting—Lumigrow LU50001) for 4 additional weeks. Plants were then moved to a growth chamber for deacclimation at a constant temperature of 5, 7, 10, 13, & 15°C with a 12-hour photoperiod. Plants were deacclimated for 1, 2, 3, 7, & 14 days at each temperature. Plants were transferred from acclimation chambers on different days to allow synchronizing of the freezing treatment. There were 25 different treatments (5 temperatures × 5 deacclimation time points). Plants were assigned randomly to each treatment after cold acclimation. Plants were separately grouped for freezing as follows: group 1- 1, 2, & 3 days of deacclimation; group 2 - 7 days of deacclimation; and group 3 - 14 days of deacclimation. Deacclimation at 5°C is essentially the same as cold acclimation. Thus, a subset of plants (those given 7 and 14 days of deacclimation at 5°C) received 5 or 6 weeks of cold-acclimation respectively. Plants were randomly placed within the freezing chamber. Freezing treatment was initiated at around noon starting at 15°C and ramping down to 5°C over the next five hours, then ramped down to the freezing temperature (−12°C) over eleven hours (4:00 AM), and held at -12°C for 4 h before ramping back up to 0°C, over 1 hour (h), and then back up to 15°C by noon the following day (lights were turned off at 5:00 PM when plants had reached 5°C and then turned on again at 8:00 AM during the last hour of freezing temperature). Plants were moved to the greenhouse and were scored for visual damage on a 0–3 scale with 0 being dead, 1 having >50% foliar damage but maintaining at least one living meristem, 2 having between 50% and 10% foliar damage, and 3 having 0–10% foliar damage after a one-week recovery period. The whole experiment was run twice.</p><p><br></p>

Tags: canola, deacclimation, freezing
Organization: Department of Agriculture