Lipid and fatty acid changes linked to postharvest needle abscission in balsam fir, Abies balsamea

Key messageThe concentration of all fatty acids decreases during abscission in balsam fir, though saturated fatty acids decrease the least. The ratio of saturated:unsaturated fatty acids is strongly correlated with abscission.AbstractPostharvest needle abscission is a huge challenge in the balsam fir Christmas tree and greenery industry. It was hypothesized that lipid and fatty acid changes postharvest are linked to needle abscission. Branches were cut, hydrated in the lab to determine needle loss and water uptake. Other branches were sampled weekly for membrane injury, and lipid and fatty acids (FA). Total polar lipid and fatty acids decreased significantly (p<0.001) postharvest. The major lipids, monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol, changed significantly from 33 and 28% to 11.5 and 13%, respectively, at the end of the experiment. Most FA in fresh balsam fir needles were polyunsaturated fatty acids (PUFA), which were three times higher than saturated fatty acids (SFA). All fatty acids decreased significantly (p<0.05) as abscission progressed, though SFA decreased the least over time. The concentration of PUFA decreased by 78%, MUFA decreased by 74%, and SFA decreased by only 46%. The ratio of saturated to unsaturated fatty acids positively correlates with abscission using Spearman's correlation coefficient (r(s)=0.833). This research contributes to the current knowledge of postharvest physiology in balsam fir to help find a way to mitigate needle loss and offer a solution to Christmas tree farmers.