GRAFTING, THE TECHNIQUE OF JOINING TWO PLANT PARTS TOGETHER, IS AN ANCIENT TECHNIQUE THAT IS USED TO PROPAGATE PLANTS. MANY INDUSTRIES RELY ON GRAFTING TO SUCCESSFULLY GROW ECONOMICALLY SIGNIFICANT SPECIES, SUCH AS APPLES, WHERE DESIRABLE VARIETIES ARE GRAFTED ONTO HARDY ROOTSTOCKS. THE ABILITY OF TWO DIFFERENT VARIETIES OR SPECIES TO GRAFT IS CALLED GRAFT COMPATIBILITY. WHILE THE PROCESS OF GRAFTING HAS EXISTED FOR THOUSANDS OF YEARS, THE MECHANISMS THAT UNDERLIE GRAFT COMPATIBILITY REMAIN POORLY UNDERSTOOD. DUE TO THIS, GRAFT COMPATIBILITY IS DETERMINED THROUGH TRIAL AND ERROR. TRIAL-COMBINATIONS ARE NOT ALWAYS EASILY DIAGNOSED AS INCOMPATIBLE. A TYPE OF GRAFT INCOMPATIBILITY, CALLED DELAYED INCOMPATIBILITY, OCCURS WHEN GRAFTS APPEAR TO BE SUCCESSFUL ONLY TO FAIL MONTHS OR YEARS LATER. BECAUSE WOODY CROPS ARE SLOW-GROWING AND CHALLENGING TO USE IN RESEARCH, LITTLE IS KNOWN ABOUT THE MOLECULAR BASIS THAT LEADS TO GRAFT INCOMPATIBILITY. THIS PROJECT UTILIZES A NON-TREE MODEL SYSTEM: TOMATO AND EGGPLANT GRAFTED AS COMPATIBLE PARTNERS AND TOMATO AND PEPPER GRAFTED AS INCOMPATIBLE PARTNERS. ALL OF THESE PLANTS ARE FAST GROWERS AND EASILY STUDIED IN A RESEARCH ENVIRONMENT.PREVIOUS WORK HAS SHOWN THAT COMPATIBLE GRAFTS REQUIRE A COMPLEX NETWORK OF MOLECULAR AND HORMONAL SIGNALING. THIS PROJECT WILL INVESTIGATE THE ROLE THAT THESE SIGNALS PLAY IN GRAFTING. WE WILL DO THIS BY ANALYZING KNOWN MOBILE SIGNALS AND SIGNAL TRANSPORT IN BOTH COMPATIBLE AND INCOMPATIBLE GRAFTED PLANTS. WE WILL ALSO ASSESS IF NECROSIS (TISSUE DEATH) IN THE GRAFT JUNCTION CORRELATES WITH BLOCKED INTERCELLULAR TRANSPORT. THROUGH THIS PROJECT, WE AIM TO ADVANCE THE UNDERSTANDING OF GRAFT BIOLOGY. A BETTER UNDERSTANDING OF GRAFT COMPATIBILITY WILL BENEFIT BREEDERS AND GROWERS WHO ARE NEGATIVELY AFFECTED BY THE LOSS OF CROPS DURING GRAFT INCOMPATIBILITY.