Genetic transformation is central to the discovery, delivery, and functional analysis of genes, and for associated crop improvement, and yet is technically challenging in many plant species. As an example, cucumber (Cucumis sativus L.) is a model species for the study of phloem characteristics, raffinose family oligosaccharide (RFO) metabolism and sex determination, but methods for its genetic transformation have generally had low efficiency, thereby limiting basic and applied studies. Here, we describe a rapid and efficient protocol for Agrobacterium-mediated transformation of cucumber cotyledon explants, using vacuum infiltration. The transformation efficiency of the regenerated plants was as high as 54%, and the final positive plantlet transformation efficiency was approximately 26% of the total number of infected explants and this is obviously higher than previously published protocols. Transgenic plantlets can be obtained in 3 to 4 months and the transgenic T1 seeds generated in the subsequent 3 to 4 months after self-pollination. Using this protocol, we have obtained more than 600 transgenic cucumber lines. This protocol is of great importance for studies of cucumber and of other Cucurbitaceae species, since it enables gene functional analysis, and so opens a pipeline for rapid cucumber variety improvement.

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