TABLE 1.
Examples of graft-induced transcriptional and epigenetic changes and physiological effects in woody species.
| Woody species | Graft-induced transcript/epi-genetic mark or mobile signal | Graft system | Tissue | Molecular response | Potential physiological change/agronomical trait | References |
| Avocado (Persea americana) | miRNA | Seedling rootstocks and scions, Clonal rootstocks and mature scionwood (budwood) | Leaves (Scion) | miRNA induction in scion leaves | Transition from juvenile to flowering phase | Ahsan et al., 2019 |
| Cassava (Manihot esculenta) | siRNAs | Non-transgenic scion/transgenic rootstock | Leaves (scion) | Translocation of siRNA from rootstock to scion, graft-induced systemic silencing | Resistance to CBSD virus | Yadav et al., 2011 |
| Blueberry (Vaccinium corymbosum) | Hormonal Signaling | Non-transgenic scion/transgenic rootstock | Leaves (scion) | Phytohormones induced by transgenic blueberry (T) carrying a 35S-driven blueberry FT (VcFT-OX) | Flower induction | Song et al., 2019b |
| Grapevine (Vitis vinifera) | miRNA | Reciprocal heterografts Cabernet Sauvignon/M4 | Leaves (scion) and roots (rootstock) | A series of conserved and novel miRNAs either in scion or rootstock are up- or down-regulated depending on drought conditions and rootstock | Differential drought-response | Pagliarani et al., 2017 |
| Grapevine (Vitis vinifera) | mRNAs | Cabernet Sauvignon/41B Cabernet Sauvignon/1103 Paulsen | Leaves (scion) | Differential expression of genes associated with photosynthesis, secondary metabolism, hormonal signaling, stress response depending on rootstock | Vigor, productivity Biotic stress resistance | Chitarra et al., 2017 |
| Grapevine (Vitis vinifera) | mRNAs | Reciprocal combinations of Pinot Noir and 1103 Paulsen | Roots (rootstock) | Differential graft-induced gene expression in roots depending on scion-rootstock combination | Root response | Gautier et al., 2020 |
| Cherry (Prunus avium) | siRNA | Non-transgenic scion/transgenic rootstock | Leaves (scion) | Translocation of siRNA from rootstock to scion, graft-induced systemic silencing | Resistance to PNRSV virus | Song et al., 2013; Zhao and Song, 2014 |
| Apple (Malus domestica) | miRNA | Heterografts with susceptible and resistant rootstocks | Leaves (scion) | miRNA induction in scion leaves | Resistance to fire blight | Kaja et al., 2015 |
| Apple (Malus domestica) | miRNA | Three apple materials were analyzed: M9, Fuji, and Fuji/M9 | Leaves (scion) | A regulatory network between miRNAs and mRNAs that is generated by grafting | Flower formation | An et al., 2018 |
| Apple (Malus domestica) | DNA methylation | GDDH13 line grafted on scion cultivar “MM106” | Leaves (scion) | Differential DNA methylation | Mother plant DNA methylation pattern transmitted to graft | Perrin et al., 2020 |
| Orange (Citrus sinestis) | DNA methylation | Valencia orange scion grafted on Rangpur Lime (RL) and Sunki Maravilha (SM), two rootstocks with different drought responses | Leaves (scion) | Differential DNA methylation under recurrent water stress | Increased “memory of stress” in the VO/SM combination | Neves et al., 2017 |
| Tahiti acid lime (Citrus latifolia Tanaka) | DNA methylation | Tahiti acid lime grafted on RL and SM | Leaves (scion) | Differential DNA methylation under recurrent water stress | Similar physiological responses | Santos et al., 2020 |