Lack of genetic diversity can potentially limit the ability of cropping systems to resist unknown or evolving pests, pathogens, or adverse environmental conditions. A major frustration in the diversity debate is that there is no clear definition or concise measure of genetic diversity at the farm level. The empirical evidence on the diversity - productivity relationship is also extremely limited. The objectives of the proposed research are: 1) to define and develop the concept of indices to measure genetic diversity in farmers' fields and assess the extent of genetic diversity in wheat production system and 2) to quantify the impact of genetic diversity on crop productivity and variation in output. Detailed country case studies of China and Australia will be used to explore these issues. By providing a better understanding about the relationship between genetic diversity and wheat productivity and stability in yield, the researchers will be able to identify the extent of variety mix that farmers can plant to ensure stable wheat yields over time. In this project, the researchers will also identify i) economically important traits that require breeders attention and from which source material may be available from CIMMYT; and ii) gaps in CIMMYT germplasm collections that could potentially be filled by Chinese materials.