Strigolactones: From Fundamental Biology to Applications in Tree Breeding.

Strigolactones (SLs) are small carotenoid-derived signaling molecules that serve as both rhizosphere chemical cues and well-recognized endogenous plant hormones. They are involved in shoot branching inhibition, root system remodeling, mycorrhizal symbiosis, and diverse stress responses in plants. This paper systematically reviews the biosynthesis and metabolism of SLs, the perception and signaling mechanisms, their translocation and long-distance transport in planta, as well as how SLs modulate key traits of forest trees via crosstalk with other hormones, including auxin, cytokinin, abscisic acid, etc. Based on current technical platforms such as tissue resolved liquid chromatography tandem mass spectrometry (LC-MS/MS), isotope labeling, tissue specific clustered regularly interspaced short palindromic repeats (CRISPR) and inducible expression systems, grafting assays, and semifield long-term monitoring, this study proposes a research and breeding roadmap progressing from molecular validation to medium- and short-term characterization in model trees and finally to multisite long-term ecological assessment. It also provides recommendations covering risks, benefits, and regulations concerning the use of chemical analogs, gene editing, and grafting strategies in forest cultivation. This review presents a multiscale theoretical framework and testable pathways for translating SLs research from model plants to forestry applications.