Foxtail mosaic virus-induced flowering assays in monocot crops.

Virus-induced flowering (VIF) exploits RNA or DNA viruses to express flowering time genes to induce flowering in plants. Such plant virus-based tools have recently attracted widespread attention for their fundamental and applied uses in flowering physiology and in accelerating breeding in dicotyledonous crops and woody fruit-trees. We now extend this technology to a monocot grass and a cereal crop. Using a Foxtail mosaic virus (FoMV)-based VIF system, dubbed FoMViF, we showed that expression of florigenic Flowering Locus T (FT) genes can promote early flowering and spikelet development in proso millet, a C4 grass species with potential as a nutritional food and biofuel resource, and in non-vernalized C3 wheat, a major food crop worldwide. Floral and spikelet/grain induction in the two monocot plants was caused by the virally expressed untagged or FLAG-tagged FT orthologs, and the florigenic activity of rice Hd3a was more pronounced than its dicotyledonous counterparts in proso millet. The FoMViF system is easy to use and its efficacy to induce flowering and early spikelet/grain production is high. In addition to proso millet and wheat, we envisage that FoMViF will be also applicable to many economically important monocotyledonous food and biofuel crops.