Abstract: Loquat (Eriobotrya japonica Lindl.) is a valuable subtropical fruit tree whose genetic improvement has been significantly constrained by the absence of an efficient genetic transformation system. Although Agrobacterium-mediated transformation is the most widely used method, it proves ineffective in loquat due to the species' recalcitrance to in vitro regeneration. Pollen-based transformation offers a promising alternative by bypassing the need for tissue culture. However, the pollen wall poses a major physical barrier to the uptake of exogenous DNA. In this study, we investigated magnetic nanoparticle (MNP)-mediated transformation as a novel strategy for loquat. We confirmed that loquat pollen contains tricolporate apertures with diameters ranging from 3.0 to 5.0 μm, which are structurally suitable for the entry of MNPs–DNA. Based on this finding, we developed and optimized a transformation protocol using polyethyleneimine-coated Fe₃O₄ nanoparticles to deliver genetic material into loquat pollen grains. Using this approach, we successfully generated stable transgenic loquat lines, including both overexpression and gene-edited mutants. To our knowledge, this is the first report of successful MNP-mediated pollen transformation in a woody plant species. This work establishes a robust and efficient genetic transformation platform for loquat, providing a valuable tool for functional genomics and molecular breeding, as well as a potentially applicable strategy for other recalcitrant woody plants.

Key words: gene editing, loquat, magnetic nanoparticle, over-expression, pollen