2017 ASHS Annual Conference

Postharvest abscission is a huge problem for Atlantic Canada's balsam fir industry. It is hypothesized that fatty acid changes are linked to cell damage postharvest and that genotypic differences occur. Branches were collected from two clones of balsam fir (AB-NSD-124 and AB-NSD-005), the first previously identified as a high NRD (needle retention duration) clone postharvest and the latter a low NRD clone. Five samples of each genotype were collected onsite and frozen in liquid nitrogen and stored in a -80 °C freezer for lipid analysis. Branches from the high and low NRD clones were transferred to the lab, hydrated, and kept at an average temperature of 20-24 °C and a light intensity of 85 - 100 μmol m⁻²·s⁻¹. Needle loss (mgg^-1fw) and average daily water use were measured three times a week. Membrane injury (MII), fluorescence index, and capacitance were measured on site and weekly. Lipids were extracted and analyzed. There was a significant interaction between time and genotype (p =.003). By week 9, there was 4x the needle loss in AB-NSD-005 as in AB-NSD-124. Needle loss in AB-NSD-005 was best predicted by increasing MII and decreasing capacitance (R²adj= 75.9%), whereas in AB-NSD-124 it was decline in fluorescence (R²adj= 75.6%), indicating that AB-NSD-124 was more affected by chloroplast breakdown. Needle loss in AB-NSD-005 was weakly but significantly related to peroxidation index (PI) and double bond index (DBI), whereas needle loss in AB-NSD-124 could be predicted by decreasing PI, DBI, and linoleoyl-desaturase ratio (LDR; R²adj= 58.68%), suggesting the production of fewer 18:3 fatty acids over time. Significant interactions between time and genotype indicate that PI and DBI indices decrease much earlier in AB-NSD-005. The most notable interaction in fatty acids was seen in 18:3n3 with a 32% and 35% decline in AB-NSD- 124 and AB-NSD-005, respectively. However by the fifth week, in AB-NSD- 124 there was no change in 18:3n3 whereas in AB-NSD-005 there was a significant decrease. All these lipid and fatty acid changes suggest a significant link between lipid and fatty acid metabolism and postharvest needle abscission and it is hypothesized that lipids could be a potential signal molecule in postharvest needle abscission.