Alternative Agrobacterium Method Bypasses Tissue Culture to Multiply Sweet Potato Cultivars

Chinese scientists were able to multiply sweet potatoes by utilizing both Agrobacterium rhizogenes and the crop's natural transgenic trait. Their method skips the need for tissue culture to obtain genetically modified sweet potato plants.

According to previous studies, sweet potato is a naturally transgenic plant that contains two Agrobacterium transfer DNAs: IbT-DNA1 and IbT-DNA2. On the other hand, Agrobacterium rhizogenes has two transferable TNA regions: TR-DNA that corresponds to IbT-DNA1 and TL-DNA to IbT-DNA2. The scientists theorized that this bacterium-plant relationship is more symbiotic than parasitic, and that Agrobacterium rhizogenes can be used to induce hairy roots upon wounding and infecting plant leaves or stems. The hairy roots may then contain the T-DNA of the bacterium's binary vector if co-transferred, and these roots may serve as adventitious roots with the potential to develop into storage roots with heritable genetic modifications.

To test their hypothesis, the scientists used Shangshu 19 sweet potato variety. They inoculated its vine cuttings with Agrobacterium rhizogenes K599-IbRPS5a:GUS and planted them under natural field conditions where they also induced hairy roots and plant growth. Initial PCR testing found that nearly 100% of the infected vine cuttings could produce transgenic positive storage roots. Whole plants were regenerated and underwent qRT-PCR analysis which showed that 90-100% of the infected plants formed positive storage roots.

The study determined that the Agrobacterium rhizogenes method is faster, simpler and more efficient than having to go through tissue culture. The researchers also concluded that the hairy root lines established from single root meristems are cellular clones, and every transgenic storage root represents an independent transformation event.

More details from Plant Biotechnology.