EXPEDITING ROOTSTOCK AND SCION BREEDING FOR COLD AND DROUGHT TOLERANCE BY PREDICTING HORMONE SIGNALING INTERACTIONS

The most productive fruit trees result from grafting well-adapted, disease resistant, and stress-resilient rootstock with high-bearing, desirable scion (shoot tissue). In many casesgrafted combinations are even more than the sum of their parts, as strong synergy between rootstock and scion can result from hormone signals transmitted between the tissues, which have different genetic makeups.Our major goal is to identify the mechanisms and breeding targets throughwhich apple rootstock tissues can provide apple scion tissue with the ability to resist late frosts, which result in significant reductions in deciduous fruit productivity. We have identified several rootstocks that increased the frost resilience of two scion varieties in the field in 2020.Our objectives are to (1) identify hormone-mediated interactions between rootstock and scion through paired transcriptomics and hormonal profiling of a panel of rootstock-scion pairs, and (2) validate high throughput molecular assays for functional characterization of hormone perception in deciduous fruits. Through this pairing of systems and synthetic biology we will identify and validate breeding targets and grafting strategies which will increase the resilience of fruit trees to osmotic stress events such as frost and drought.