2019 ASHS Annual Conference

Several studies have suggested that postharvest needle retention in balsam fir increases in autumn due to cold acclimation, and that this is more evident in Christmas tree genotypes with lower postharvest needle abscission resistance (NAR). The objective of this study was to compare the fatty acid profiles of low needle abscission resistant genotypes to high needle abscission genotypes. In a 4 x 4 factorial experiment, four genotypes of balsam fir, clones 9, 37, 506 and 566, were sampled for fatty acids at five time periods, ranging from September, 2013 and February 2014. In addition, opposite branches on the stem were transferred to the lab, hydrated and monitored to determine mean needle abscission commencement (NAC) and peak needle abscission (PNA). Abscission commenced after 52, 42, 75, and 32 days in clones 9, 37, 506, and 566, respectively. Peak needle abscission occurred at a mean of 57, 50, 80, and 36 days, respectively. Clone 506 had significantly better needle retention than all other genotypes in each of the sampling periods (p < 0.001). All genotypes commenced needle abscission significantly earlier when collected in February than when collected in September through December (p< 0.001), possibly related to a January thaw. Fluorescence was significantly (p< 0.05) linked with photoperiod(R²= 0.542). Δ5-UPIFA composed > 20% of fatty acids in all clones, 5,9-18:2 (taxoleic), 5,9,12-18:3 (pinolenic), 5,9,12,15-18:4 (coniferonic), 5,11,14,17-20:4 (juniperonic), and 5,11,14-20:3. There were many significant interaction and main effects between date sampled and clone (p< 0.05).There was a significant decrease in 16:0 and 16:1 between September and February. There was a significant increase in unsaturated acids 18-2 cis (linoleic acid) and 5, 9, 12-18:3 (pinolenic acid). There was a significant increase in FA with a chain length greater than 20. There was a significant decrease in 5,9 -18:2 between October and November, and again between December and February unique to Clone 506, suggesting that it could be related to its superior ability to retain needles postharvest.