Controlling the time that forage plants flower would vastly improve tools available for pasture quality management, and provide some fundamental knowledge about flowering physiology, especially in grasses.
In most flowering plants one can easily distinguish vegetative and reproductive phases of growth: during the first, only leaves, stems and roots are produced, and during the second, inflorescences bearing flowers and later seeds, will appear. Because correct timing of flowering is essential for survival, plants have complex mechanisms that regulate this transition. Many internal and external cues are evaluated, like developmental state, temperature and day length. For ryegrass to flower, for example, requires exposure to a lengthy period of cold (naturally happening during the winter), followed by a few long days of 14 hours or more, which happens naturally in spring.
Without either of these external stimuli, ryegrass plants will remain vegetative throughout the season.
Great progress has been made in understanding genetic networks in model plants like Arabidopsis thaliana. By selectively manipulating 2-3 key regulatory genes in this little annual weed (close relative of rapeseed, cabbage and radish) one can make plants that either never flower, or go into floral development straight after seed germination.
There is emerging evidence that the basic genetic relationships and the key ‘players’, or main genetic switches, are the same, or very similar in many flowering plants. The similarity extends even to plants with very dissimilar flowering physiology: genetic parallels can be drawn to at least some extent between arabidopsis and many species like rice, morning glories, snapdragons, brassicas and even trees.
In our project we are identifying these genetic switches in ryegrass. We use the knowledge developed in the model plant species to list the most promising candidate genes, and then use our collection of ryegrass EST sequences and other methods to actually identify them in the ryegrass genome, and to ascertain their functions. These genes will be used to develop plants that will lose their natural ability to flower in response to cold and long days, but will have a built-in switch that will activate floral development when an artificial signal is provided, like a spray with a certain chemical.