1. Characterization of postharvest NAR of balsam fir after natural cold acclimation
Mason MacDonald, Arumugam Thiagarajan, Rajasekaran Lada, Scott Veitch, Azure Adams
11th Annual Christmas Tree Research and Extension Conference
Dalhousie University, Truro, Nova Scotia, Canada
August 10-14, 2013

2. Introduction
Cold acclimation is thought to be necessary to promote needle retention in balsam fir
Producers in NS typically hope for a few frost events before harvest
Warm autumns results in noticeable decrease in needle retention
Metabolic shifts in hormones, sugars, and lipids associated with cold acclimation

3. introduction
Artificial cold acclimation promotes needle retention (Thiagarajan, 2012)
Balsam fir seedlings pre-exposed to a variety of temperatures
Significantly improved retention at pre-exposure to 4°C
5-fold increase in root ABA
2.5-fold increase in shoot ABA

4. introduction
Hypothesis: natural cold acclimation will improve needle retention in balsam fir
Objectives:
To determine the effect of natural cold acclimation on postharvest needle abscission
To identify physiological changes indicative of cold acclimation
To identify a potential time to harvest trees with superior needle retention

5. Methods – experiment 1
Samples collected from Debert, NS and Fredericton, NB in three field seasons
95 branches in
93 branches
208 branches
Design was 2 x 3 factorial
Factor A: harvest (October versus January)
Factor B: NAR (low, moderate, or high)
Response: Needle abscission

6. Methods – experiment 2 Samples collected from Debert, NS each month
September to January
Factor A: month
Factor B: NAR
Response variables
XPP
MII
Capacitance
Raffinose/galactose
ABA

7. Results – experiment 1 2007-2008 season
Clear separation of low, moderate, and high NAR in Oct.
Significant improvement in low and moderate NAR
No improvement in high NAR

8. Results – experiment 1 2008-2009 season
Clear separation of low, moderate, and high NAR in Oct.
Significant improvement in low NAR
No improvement in moderate NAR
Decrease in high NAR

9. Results – experiment 1 2010-2011 season
Clear separation of low, moderate, and high NAR in Oct.
Significant improvement in low NAR
Decrease in moderate NAR
Decrease in high NAR

10. Results – experiment 2
Significantly higher needle retention in Nov or Dec

11. Results – experiment 2
At some points, the low NAR genotypes out perform the high!

12. Results – experiment 2
Cold acclimation from October to January was not beneficial
Cooler autumn, trees may have acclimated earlier
“Genotypic convergence” still occurred

13. Results – experiment 2

14. Results – experiment 2

15. Results – experiment 2

16. summary “Genotypic convergence”
Low NAR genotypes tend to benefit from cold acclimation
High NAR genotypes do not benefit, but may decrease
Superior needle retention was observed in November or December in all NAR classes
Clear trends in capacitance, raffinose, galactose, and ABA over time
Indicative of cold acclimation
Does not distinguish among NAR classes