Morphological, Physiological and Gene Expression Modulation of Apple Scions By Apple Rootstocks

Apple scion varieties have been grafted on dwarfing apple rootstocks for several hundred years to increase productivity and early bearing of trees.  Recently, we have been able to describe several other rootstock-induced morphological and physiological effects beyond dwarfing and early bearing including branch angle modification, induction of sylleptic branching, nutrient aquisition, reduction in chilling requirements.  Apple rootsocks were the first crop where rootstock-induced gene expression modulation in scions was described.  We describe a series of experiments aimed at understanding the genetic basis of these rootstock induced changes leveraging breeding populations, QTL and eQTL  approaches and phenotyping of composite trees.