Dwarfing of fruit trees: from old cognitions to new insights

Abstract Plant dwarfing is a key agronomic trait, often characterized by shortened internodes and increased branching and leaf production, which improves lodging resistance and facilitates intensive crop planting. In fruit crops, dwarfing promotes dense planting, enhancing land utilization and simultaneously boosting fruit yield and quality, thus driving higher economic returns with reduced labor costs. Significant advancements have been made in elucidating the mechanisms underlying fruit tree dwarfing despite their complex genetic backgrounds, largely due to the rapid progress in modern molecular technologies. This article reviews the morphological and physiological features of dwarfing in fruit trees and examines the molecular regulatory mechanisms, with a particular focus on plant hormones such as gibberellins, auxins, brassinosteroids, and abscisic acid. Furthermore, this review highlights future research directions, including the identification of hormone-related dwarfing determinants, the dissection of comprehensive molecular regulatory networks using cutting-edge techniques like single-cell sequencing, high-resolution microscopy, in situ imaging, and multi-omics approaches. These new insights into fruit tree dwarfing lay a solid foundation for a deeper understanding of plant growth regulation in a new era, offering promising avenues for controlling plant growth through manipulation of key factors, especially hormones, or for the development of new cultivars or rootstocks with stable dwarf phenotypes via molecular breeding, ultimately advancing fruit productivity in the future.