Rice Genotype Variation in Leaf-Grain Element Concentration Associations.

As a major food crop of the world, rice can also be a major source of mineral nutrients for much of the world's population. The control of accumulation of particular elements in the grain varies by element. There is considerable variation among rice genotypes for concentrations of specific elements in grain; this variation can be exploited to determine the genes and systems biology behind the controls. Some of the control exists at the soil chemistry level, and in different aspects of plant physiology. This study identifies and analyzes variation in leaf element concentrations among rice genotypes exhibiting high or low grain concentrations under flooded or unflooded conditions. The analysis helps delimit the nature of particular controls and helps identify potential parents for populations to examine leaf-level control of rice grain element concentrations. Unlike in grain, where there are few associations among element concentrations besides the apparent phytate complex and the Calcium-Strontium analogue relationship, in leaves there are several wide-spread and fairly strong associations among elements. In addition to the Calcium-Strontium and Potassium-Rubidium analogue associations, there are a handful of other associations among elements. A couple of these associations ‘carry over’ from leaves to grain in certain genotypes. The possibility exists to screen for these element complexes in vegetative-stage leaves of progeny derived from these genotypes, thereby helping identify mechanisms and genes affecting element accumulation in grain and accelerating breeding efforts aimed at improving rice grain nutritional value.