Abstract
Grafting is a common practice for vegetative propagation and trait improvement in horticultural plants. A general prerequisite for successful grafting and long term survival of grafted plants is taxonomic proximity between the root stock and scion. For the success of a grafting operation, rootstock and scion should essentially be closely related. Interaction between the rootstock and scion involves complex physiological-biochemical and molecular mechanisms. Successful graft union formation involves a series of steps viz., lining up of vascular cambium, generation of a wound healing response, callus bridge formation, followed by vascular cambium formation and subsequent formation of the secondary xylem and phloem. For grafted trees compatibility between the rootstock/scion is the most essential factor for their better performance and longevity. Graft incompatibility occurs on account of a number of factors including of unfavorable physiological responses across the graft union, transmission of virus or phytoplasma and anatomical deformities of vascular tissue at the graft junction. In order to avoid the incompatibility problems, it is important to predict the same at an early stage. Phytohormones, especially auxins regulate key events in graft union formation between the rootstock and scion, while others function to facilitate the signaling pathways. Transport of macro as well as micro molecules across long distances results in phenotypic variation shown by grafted plants, therefore grafting can be used to determine the pattern and rate of recurrence of this transport. A better understanding of rootstock scion interactions, endogenous growth substances, soil or climatic factors needs to be studied, which would facilitate efficient selection and use of rootstocks in the future. Protein, hormones, mRNA and small RNA transport across the junction is currently emerging as an important mechanism which controls the stock/scion communication and simultaneously may play a crucial role in understanding the physiology of grafting more precisely. This review provides an understanding of the physiological, biochemical and molecular basis underlying grafting with special reference to horticultural plants.
Highlights
Grafting has been performed in agriculture since the beginning of civilization
Lot of effort has been put into studying the physiological mechanism of union formation, causes and consequences of graft incompatibility and as to how molecules are being transferred across the graft unions to reveal the mechanisms responsible for inducing the phenotypic changes by grafting
The results indicate that tongue grafting is the best method of propagation for peach variety Shane-Punjab (Sharma et al, 2018)
Summary
Grafting has been performed in agriculture since the beginning of civilization. Historical records have revealed that ancient Chinese and Greeks have been practicing it since 1560 B.C. (Melnyk and Meyerowitz, 2015). The superiority and quality of the grafted crops further led to widespread adoption of this technique It is a wellestablished practice which makes it possible to physically join two or more genetic entities in a single tree to influence the productivity characters of a tree favorably and facilitates asexual propagation in horticultural crops like apple, pear, plum and cherry (Figures 1A–D; Kumari et al, 2015). A “de novo” formed meristematic area must develop between scion and rootstock for a successful graft union. The scion becomes the new shoot system and the rootstock (under stock, stock) forms the root system of the grafted plant. Success of a grafting operation depends on the strength of the union formed. Graft union formation depends on a number of factors viz., molecular pathways and physiological/biochemical responses. In this review we get an idea about the fundamental mechanism of graft union formation, graft incompatibility: its types, mechanism and causes, but it makes some of the critical molecular and physiological mechanisms associated with grafting much easier for us to understand
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
