A Review on Advances in Dwarfing Fruit Trees: Current Trends and Future Perspectives

Abstract

Dwarfing of fruit trees is a central breeding strategy to increase orchard productivity, efficiency of input use as well as fruit yield and quality. By decreasing tree vigor (maturity period) and size, dwarfing increases the potential for high-density planting, simplifies orchard operations and induces early precocious fruit production to meet the requirements of present-day intensive fruit culture. This review provides a synthesis of new developments in dwarfing technology via scion stock relationship, which are discussed with respect to practical effects on fruit crops, along with the recent progress and prospects to determine challenges for this purpose. New Stock union systems involving dwarfing rootstocks (e.g. M.9 for apples) and inter-stocks have revolutionised management and maximized yield. These approaches capitalize on these physiological and molecular processes, involving a modified hydraulic conductance, hormonal signalling and QTL gene transfer (e.g.,cDw1 in apple), to reduce tree size by 30–70% from standard rootstocks while increasing fruit set and quality. e.g. tetraploid rootstocks in citrus reduce canopy volume up to 20–30% and Geneva series rootstocks in apples are dwarfing resistant rootstocks. Then interstock grafting involving cultivars like SH40 in apples is in addition able to further modulate vigor under stress conditions showing the capacities for adaptation to environmental constraints.  These innovations allow for high-density orchards, enhancing light interception, and photosynthesis efficiency and economic return. Furthermore, advances in molecular understanding of graft union physiology and gene expression are improving dwarfing precision by providing customized solutions for crops such as apple, citrus, and pear. However, challenges remain such as rootstock-scion incompatibility, variability of performance under different climates and for a few fruit species limited dwarfing options. New cell technologies, for example CRISPR-mediated editing, can be combined in the future to create new dwarf rootstocks with improved stress tolerance and compatibility. Moreover, sensing-based precision agriculture systems can be used to maximize the dwarfing effects in different farming systems. These challenges will need to be addressed through interdisciplinary research which optimises the benefits of dwarfing with long term sustainability. This conclusion emphasizes the transformation of fruit production that can be achieved by grafting-based dwarfing, and expresses its parameter for success in global food security.