Leaves need to live longer

Developing crops that use water more efficiently is one of the greatest challenges facing crop scientists today. In the face of diminishing water resources, the world is expected to consume twice as much food in the next 50 years as it has in the past 10,000 years.

To meet this demand, world grain production will need to increase 40 percent by 2020.

Crops such as sorghum and millet are well adapted to semi-arid regions, and contain mechanisms enabling these crops to resist drought. Understanding the genetic, physiological, molecular and biochemical basis of such drought-resistance mechanisms is fundamental to the development of new strains that are better adapted to dry conditions.

Keeping leaves alive longer is a fundamental strategy for increasing crop production, particularly under water-limited conditions. Recent studies in Australia have examined two sources of "staygreen" derived from sorghum lines native to Ethiopia and Nigeria.

Young stay-green hybrids partition more carbon and nitrogen to leaves, resulting in higher specific leaf nitrogen (SLN). As well as enhancing factors such as transpiration efficiency, higher SLN also delays the onset and slows the rate of leaf ageing, and this is associated with stay-green crops taking up more nitrogen from the soil.

These processes lead to increased grain yield and lodging resistance in stay-green lines under drought conditions.

Extract from the proceedings of the 11th Australian Agronomy Conference, Geelong, 2003. GRDC Program 2