The 2012 ASHS Annual Conference

Postharvest needle loss in Balsam fir Christmas trees is a major issue in the Atlantic Canadian Christmas tree industry.  It results in significant losses in income to producers and dissatisfaction with real trees among consumers, which may carry forward many years.  Needle loss is a consequence of complex interactions among many factors, including genetic variations.  A genetic tendency to either retain or shed needles postharvest has been observed.  A study was completed to determine needle retention duration (NRD) of 206 Balsam fir clones located at the Tree Improvement Unit, Department of Natural Resources in Island View, New Brunswick, Canada.  NRD was observed for both pre- and post-cold acclimation periods over the 2010/2011 and 2011/2012 seasons.  Branches with two year old growth were collected on September 27, 2010, January 11, 2011, September 27, 2011, and January 11, 2012 and transported in water to the Christmas tree Research Centre, Truro, Nova Scotia, Canada.  Branches were allowed to equilibrate to ambient laboratory conditions prior to experiment set up for 48 hours.  Following a fresh cut, the branch weight was recorded and each branch was placed on a white, 8 x 10” foam tray at room temperature (21 °C ± 1 °C) under 24 hour fluorescent lighting (15 µmol·m^-1·s^-2).  Needle loss was monitored every second day.  Branches were gently brushed between the thumb and two fingers 5-6 times and the detached needles were collected and weighed.  A final weight of each branch was taken when all of the needles had fallen.   Clones with both high NRD and low NRD were identified.  The highest NRD was 43 days while the lowest was only 7 days.  Interestingly, in low NRD clones needle retention improve after cold acclimation, however clones with a high NRD pre-cold acclimation needle retention decreased post- cold acclimation.  This phenomenon has been observed in other studies in Nova Scotia as well.  Also, NRD for high NRD clones dropped by about 10 days in year 2 while low NRD clones increased by about 8 days in year 2.  The growing season in year 2 was abnormally stressful with higher than normal rainfall and a large gall midge infestation.  It is thought that the trees were showing symptoms of this added stress by altering their NRD similar to what was seen during cold acclimation. In summary, there appears to be a genetic plasticity among genotypes for NAR, which is modulated depending on cold acclimation.