Substantially increasing the productivity of water used in agriculture is essential to meet goals of food and environmental security. Achieving these increases requires research that spans scales of analysis and disciplines. In spite of its importance, we do not have a common conceptual framework and language to facilitate research and communication among stakeholders. The objective of this chapter is to propose a common conceptual framework for water productivity. In a broad sense, productivity of water is related to the value or benefit derived from the use of water. Definitions of water productivity differ based on the background of the researcher or stakeholder. For example, obtaining more kilograms per unit of transpiration is an important means of expressing productivity of water when the interest of analysis is crops. At the basin scale, obtaining more value from water used from irrigated and rain-fed crops, forests, fisheries, ecosystems and other uses is of importance. There are several interrelated definitions of water productivity that are important across scales and domains of analyses. We propose in this chapter a set of definitions for water productivity and show how these are related across scales.As the analysis moves from individual plants to fields, farms, irrigation systems and water basins, different processes and means of analysis are important. Understanding how measures of water productivity scale up and scale down provides the key to how a group of people of diverse disciplines can work together on this topic. For example, crop scientists and breeders may focus on obtaining more mass per unit of transpiration, while planners and economists may consider policies to allocate water and land resources between different uses. To capture the full benefits of improved water productivity at farm level, it is necessary to integrate these with system-and basin-level changes. We provide a framework to show the interrelationship of the work of various disciplines.
An restriction fragment length polymorphism (RFLP)-based genetic map of ryegrass (Lolium) was constructed for comparative mapping with other Poaceae species using heterologous anchor probes. The genetic map contained 120 RFLP markers from cDNA clones of barley (Hordeum vulgare L.), oat (Avena sativa L.), and rice (Oryza sativa L.), covering 664 cM on seven linkage groups (LGs). The genome comparisons of ryegrass relative to the Triticeae, oat, and rice extended the syntenic relationships among the species. Seven ryegrass linkage groups were represented by 10 syntenic segments of Triticeae chromosomes, 12 syntenic segments of oat chromosomes, or 16 syntenic segments of rice chromosomes, suggesting that the ryegrass genome has a high degree of genome conservation relative to the Triticeae, oat, and rice. Furthermore, we found ten large-scale chromosomal rearrangements that characterize the ryegrass genome. In detail, a chromosomal rearrangement was observed on ryegrass LG4 relative to the Triticeae, four rearrangements on ryegrass LGs2, 4, 5, and 6 relative to oat, and five rearrangements on ryegrass LGs1, 2, 4, 5, and 7 relative to rice. Of these, seven chromosomal rearrangements are reported for the first time in this study. The extended comparative relationships reported in this study facilitate the transfer of genetic knowledge from well-studied major cereal crops to ryegrass.
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