Example confocal image of a graft junction between two mutant tomato plants. A clear misconnection of the xylem can be seen within the graft junction.

Cornell University Frank Lab

NSF Research for Post-Baccalaureate Students 2021-2022

Plant grafting is an agricultural tool that involves cutting and joining various plants to increase stress resistance. The most common method is to graft the shoot of one plant (scion) to the root of a different plant (stock). After grafting, intact cells close to the graft junction adhere to the opposing tissue. Callus differentiation at the junction gives rise to the phloem and xylem. Typically, xylem strands heal in a coordinated fashion within the graft junction for a seamless reconnection; however, grafts between many species display a possible loss of communication that results in failed xylem reconnection. The cause of graft incompatibility due to failed vascular reconnection is unknown; however, finding the cause will offer more options to improve stress resistance in the face of climate change. In this project, CRISPR/Cas9 was used to knock out candidate genes that may be involved in successful grafting. After genotyping to confirm successful transformation, mutant lines are self- and heterografted with wild-type control lines to measure survival rate and vascular connectivity within the graft junction.