GRAFTING, TRANSPLANTING THE ROOTS OF ONE VARIETY OF A PLANT SPECIES WITH THE ABOVE-GROUND LEAF AND FRUIT BEARING (SCION) TISSUE OF ANOTHER VARIETY, PROVIDES A UNIQUE OPPORTUNITY TO ENGINEER DESIRABLE TRAITS IN CROPS. PARTICULARLY FOR FRUIT TREES GRAFTING IS ESSENTIAL, AS THE ROOT VARIETY CAN CONTROL THE OVERALL SIZE AND GROWTH PATTERN OF THE ABOVE-GROUND PORTION OF THE PLANT, REGARDLESS OF THE TYPICAL SIZE OF ABOVE-GROUND VARIETY. IN THIS WAY GRAFTING CAN INCREASE YIELDS AND EASE HARVESTING. ROOT VARIETIES CAN ALSO ENHANCE THE TOLERANCE OF THE ABOVE GROUND VARIETY TO STRESSES SUCH AS LATE FROSTS. HOWEVER LITTLE IS KNOWN ABOUT HOW THE ROOT VARIETIES AND ABOVE-GROUND VARIETIES INTERACT TO ENHANCE STRESS TOLERANCE AND OTHER TRAITS. LATE FROST EVENTS, FROSTS AFTER FRUIT TREES ARE IN BLOOM, CAN CAUSE NEARLY COMPLETE LOSS OF FRUIT TREE CROPS, A $10 BILLION DOLLAR INDUSTRY IN THE US. AS FULL BLOOM DATES AREMOVING EARLIER AND EARLIER DUE TO CLIMATE CHANGE, LATE FROST EVENTS WILL BECOME MOREAND MORE FREQUENT AND CATASTROPHIC.TO BETTER UNDERSTAND AND IMPROVE OUR ABILITY TO INCORPORATE FROST TOLERANCE IN FRUIT TREES THROUGH GRAFTING STRATEGIES WE AIM TO IDENTIFY THE SIGNALS COMING FROM ROOT VARIETIES THAT ARE RESPONSIBLE FOR THESE VALUABLE TRAITS SUCH AS FROST TOLERANCE. TO DO THIS WE WILL (1) IDENTIFY THE SIGNALS ASSOCIATED WITH FROST TOLERANCE IN A PANEL OF APPLE ROOT VARIETIES GRAFTED WITH THE SAME FRUIT VARIETY THROUGH PAIRED MEASUREMENTS OF GENE EXPRESSION AND CHEMICAL SIGNALS IN THE TWO TISSUES, AND (2) DEVELOP METHODS TO RAPIDLY MEASURE THE ABILITY OF DIFFERENT ROOT VARIETIES AND ABOVE-GROUND VARIETIES TO SEND AND RECEIVE THE SIGNALS RESPONSIBLE FOR FROST TOLERANCE. TOGETHER THESE RESULTS WILL PROVIDE INSIGHTS INTO ROOTSTOCK VARIETY SELECTION FOR STAKEHOLDERS SUCH AS ORCHARDS, NURSURIES, AND HOME GARDNERS. THIS WORK WILL ALSO INFORM PLANT BREEDERS ABILITY TO CREATE EVEN MORE STRESS TOLERANT VARIETIES AND PROVIDE A PROOF-OF-CONCEPT FOR APPLYING SIMILAR APPROACHES TO ENHANCE OTHER TRAITS THROUGH SELECTIVE BREEDING.