The physiological mechanism(s) of needle abscission resistance in root detached balsam fir

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Needle loss in Balsam fir threatens the survival of the 97 million dollar Atlantic Canada Christmas Tree and Greenery industry. The exact cause of needle drop is not known. Clones with high needle abscission resistance are yet to be identified and developed. The anatomical, physiological mechanisms of needle abscission resistance in root detached (RD) Balsam fir are yet to be uncovered. The initiators, the signals and the modulators of needle abscission are also not known. This project will identify the clones with enhanced needle abscission resistance and discover the initiators, signals and the mechanism and the modulators of needle abscission and regulation. We propose that needle drop in RD Balsam fir is initiated by multiple stresses (dehydration, mechanical and extreme temperatures), triggering complex yet unknown cellular signals, involving multiple plant hormones and/or certain volatiles, promoting a cascade of senescence reactions, resulting in dissolution of certain cell wall components at the point of attachment, promoting abscission. This project will lead to several discoveries relating to causal factor, signals, needle abscission physiology and needle abscission resistance mechanism(s) of RD Balsam fir. An understanding of these processes will help to screen and identify the genotypes with enhanced needle abscission resistance and develop technologies to control needle loss contributing directly to the sustainability of the Christmas tree industry to retain its competitive position and contribute to Canadian bioeconomy and human resource development.