Grafting is a traditional method for uniting one part (scion) of a plant (e.g. shoot or bud) with the root system of another. It has become a fundamental method for studying physiological, genetic and molecular aspects of long distance signalling events. There are many grafting techniques described, of which some are widely used in agriculture as a mean to facilitate asexual propagation. Advantages are to induce dwarfing and fruitfulness, avoid juvenility, promote sturdiness[1, 2] as well as facilitate domestication of both woody and non woody plant species[3, 4]. In the laboratory, grafting for most dicot species is now a well-established practice widely used to study plant nutrition, disease resistance against phloem associated pathogens[6, 7], apical dominance and shoot branching[8, 9].
Grafting has provided a powerful approach to combine diverse genotypes and investigate the transport of various long-distance signalling molecules. The technique of grafting has demonstrated that 1) the transfer of tuberigen stimulates tuberization in potato[10–12], 2) autoregulation of nodulation is regulated via long-distance shoot and root derived signals,[13–16], 3) allocation of nutrients by the Arabidopsis Na+ transporter AtHKT1 functions in the root to control Na+ accumulation in the shoot[17–20] and that the phloem mobile miRNA that acts as long-distance signal regulating phosphate homeostasis in Arabidopsis[18, 19], 4) transport of phytohormone growth molecules such as the movement of cytokinin from roots to shoots and translocation of strigolactone from root to shoot which inhibits shoot branching[22, 23], 5) the movement of secondary metabolites such as alkaloids and 6) mobile flowering signals synthesized in the leaves can stimulate flowering within the shoot apical meristem[25–28].
Hypocotyl micrografting techniques have been successfully used to study developmental and physiological processes between the root and shoot[2, 8, 29–31], while the inflorescence meristem grafting methods have generally been used to investigate the nature of signals coordinating floral reproductive growth[32–36]. Indeed small RNAs have been shown to move across the junctions from hypocotyl and inflorescence grafts, most likely via the plasmodesmata rather than the phloem[37–39]. Experiments investigating the movement of mobile signals that control apical dominance (cytokinins and auxin), nutrient uptake (phosphorus) and cellular differentiation (small RNAs) are key research areas that can benefit from the inflorescence grafting technique. Given that this technique investigates a post-floral transition, it provides a unique system to discover signals mediating reproductive development.”
This paper describes a protocol for efficient wedge-style grafting of the primary inflorescence scion to the rootstock. We define the location, timing and preparation of the floral stems for grafting. An inflorescence growth assay was developed to determine the healthiest of grafts. Histological studies confirmed the differentiation of vascular connections as well as a successful graft union.