Effective Agrobacterium-Mediated Transformation System for Eureka Lemon Using Whole Cotyledonary Node

<i>Agrobacterium</i>-mediated transformation systems using epicotyl explants have been widely used for genetic transformations of citrus. However, their application in lemons is severely constrained by browning of epicotyl tissues, which leads to an extremely low efficiency of transformation. In this study, we developed an optimized <i>Agrobacterium</i>-mediated transformation system using whole cotyledonary node explants of 'Eureka' lemon (<i>Citrus limon</i>), which significantly reduced tissue browning and enhanced transformation efficiency up to 14.48%. In addition, preparation of the whole cotyledonary node was simple and rapid, which reduced time and labor. This system facilitated efficient generation of transgenic lemon plantlets and provided a novel explant source for citrus transformation.