Mindful of this, improved sugar production in maple trees can be achieved by a combination of optimizing growth conditions for individual trees or selecting and propagating elite genotypes. These are both labor intensive programs that require gathering information from elaborately controlled experiments before prescriptions can be made or elite seedlings released to growers. Molecular biology, biochemistry, and cytology offer a set of tools that could help in assessing the genetic potential of maples at an early stage with regard to sap sweetness and tree health. Evaluation of trees in past decades has been hampered by environmental influences such as vagaries of weather, soil conditions, insect predation, and age-related effects. Seed selections from superior trees identified 50 or more years ago have been grown in progeny plantations and now show a broad range of characters, including sap sucrose levels.
Various evidence supports the idea that many genes influence sap sweetness.
Therefore the process of selecting sweeter maple trees without harmful effects due to inbreeding will require careful scrutiny at the DNA level. The present biochemical work at Proctor was initiated with the intent to correlate DNA fingerprints with the sustained occurrence of high sap sweetness. Polymorphic DNA fragments amplified from random decamer primers by the polymerase chain reaction are now being catalogued. A recent NRI grant award will accelerate this effort as well as provide a basis for mapping some of the sap sweetness genes among the sugar maple's thirteen chromosomes. However, QTLs will someday be the landmarks for selecting superior seedlings from mother trees.