High lipid perennial ryegrass growth under variable nitrogen, water and carbon dioxide supply

A novel strategy to increase the metabolizable energy content of pastures has been the development of a GM technology (HME), which when expressed in the leaves of perennial ryegrass, increases leaf lipids to 6-7% DW (approximately double ‘normal’ levels). Remarkably, increased rates of photosynthesis and growth also occur in these plants. The industry strategy is to perform field trials overseas to establish the value proposition for New Zealand. It is expected that the HME technology holds potential for future application in pastoral agriculture. A series of glasshouse pot trials revealed the influence of the HME technology on whole plant metabolism. Increases in shoot and root growth consistently occurred under high N supply. Increases in photosynthetic enzymes, major osmoticum, leaf water content and specific leaf area were recorded. A strong root growth and leaf photosynthetic response to elevated CO2 suggest possible HME growth mechanisms. Additionally, results from 2017 field trials in USA using heterozygous offspring from the HME crossing programme will be presented.