Starch produced in plant tissues represents an important component of the human diet, providing the bulk of caloric intake. Archaeological evidence points to the importance of starch in the human diet well before evidence of human civilization and crop domestication [1
]. Modern humans use huge volumes of storage starches from domesticated crops for direct food consumption, animal fodder, and a wide range of industrial purposes. Consequently, there are currently unprecedented pressures on global food and fuel supplies, due to an increasing world population (estimated to be 9.6 billion by 2050) and, at the same time, loss of agricultural land to urban growth, as well as climate change. In particular, enhanced affluence in many emerging world economies exacerbates these problems as meat consumption and automobile ownership increase, placing extra demands on crop yields to meet requests for livestock production and bio-fuels for fossil fuel replacements. Human civilization is reliant on a surprisingly narrow range of crops to supply its basic caloric requirements and of these, cereals provide the bulk of the calories in human and livestock diets. In addition, cereal starches are an important raw material for many non-food uses. Despite major advances in crop production brought about by the green revolution [2
], based on current population growth, food production must increase 50% by 2030 and double by 2050 in order to meet projected demands [3
]. The demand for higher-yielding starch-based crops is therefore greater than ever. In addition, over-consumption of carbohydrate-rich foods in some parts of the world are leading to health epidemics such as obesity and type-two diabetes [5
]. The high proportion of starch products consumed in the diet mean that this important source of calories can have a major impact on human and animal health, in particular, starch quality characteristics such as relative rates of digestibility influence blood sugar levels and lower gut (colon) health [6
]. A fundamental understanding of the process of starch biosynthesis in relation to the final structure of the starch granule and the relationship of its biochemical pathway to other metabolic pathways in plants is therefore a critical prerequisite for rational approaches to cereal crop improvement. Starch content in source leaves is recognized as an important factor governing overall plant health and productivity, as well as influencing the quality of vegetation used for grazing by livestock [7
]. Given the importance of starch as a raw material, improvements in starch yield in major crops, such as maize (Zea mays
L.), rice (Oryza sativa
L.), and wheat (Triticum aestivum
L.) will contribute greatly to food security.
In recent years, advances have been made in understanding the structural organization of the starch granule and the mechanism of starch biosynthesis in plants, in particular, storage starch synthesis in cereal endosperms. Such basic science has guided several biotechnological approaches to the improvements of starch yield and quality in both cereal and tuberous crops. Plant breeding has also resulted in yield gains of crops in the field, based on knowledge of the starch biosynthetic pathway and of source-sink relationships during plant development. It is important to realize that plant performance enhancements observed in controlled environments do not necessarily translate under field conditions. Ancestral plant genomes also hold promise for the improvement of new cereal varieties. It will be important to bridge the gap in our knowledge between the biochemical pathways involved in starch metabolism and how these biochemical processes result in the higher order structures found in all starch granules.