Efficient vegetative propagation and genetic transformation of Russian dandelion (Taraxacum kok-saghyz Rodin) from leaf explants

Russian dandelion, Kazakh dandelion, or rubber dandelion (Taraxacum kok-saghyz Rodin, TKS) is one of the most promising alternative natural rubber (NR) crops, and also the model plant for studying NR biosynthesis. However, the system for vegetative propagation and genetic transformation still remains underdeveloped for both basic and applied research in this self-incompatible and highly heterogenous species. Here we reported the efficient and repeatable vegetative propagation and genetic transformation using the leaf discs in a high-rubberproducing TKS germplasm, TK20. With the optimized hormone combination of 1 mg center dot L 1 kinetin (KT) and 0.4 mg center dot L-1 indole-3-acetic acid (IAA), an average of 15.2 normally regenerated shoots per leaf disc explant could be achieved. Base on this high-efficiency shoot regeneration technique, we have successfully transformed the TK20 via Agrobacterium tumefaciens-mediated leaf disc transformation, with the transformation rates of 40.1% and 41.2%, respectively, for the RUBY or the beta-glucuronidase (GUS)-green fluorescent protein (GFP) fusion reporter. Furthermore, the transferred genes could persist transmittable and functional in vegetative propagation through tissue culture. This is the first report that high-rubber TKS can be efficiently propagated and transformed via leaf disc cultures, and will facilitate both functional genomics research and molecular breeding in this plant species.