Found: Genes Controlling the Nutrient Content of the Rice Grain.

Biofortification refers to natural enhancement of the grain/food product through traditional breeding.  Since it does not require genetic engineering, it is acceptable to many consumers, and is compatible with organic labeling.  Enhancing the nutritional value of rice is of particular interest because rice is a primary dietary component for more than half of the world’s population, and especially so in underdeveloped parts of the world that have higher rates of malnutrition.  New marketing strategies could be employed in developed countries as well for value-added products naturally high in consumer-desired minerals such as Ca, K, and Fe; or strategically low in undesirable elements such as As or Cd.  The first step toward targeted breeding is the identification of genes responsible for orchestrating concentrations of various elements in the grain. 

Here we report the identification of quantitative trait loci (QTLs) affecting the concentrations of 16 human and plant nutritional as well as undesirable elements in brown rice grain (dehusked but  unmilled). Genetic loci were mapped among several progeny populations from biparental crosses as well as among a set of diverse rice accessions. To increase opportunity to detect and characterize grain-element QTLs, the study populations were grown under two contrasting field redox conditions, flooded (reduced soil chemistry) and unflooded (flush-irrigated to maintain aerated soil chemistry while preventing water stress).  Soil redox is known to alter mineral availability, and so was expected to affect grain mineral concentrations.  ICP-MS was used to analyze the harvested brown rice for variation in accumulation of 16 elements, namely Mg, P, K, S, Ca, Mn, Fe, Co, Ni, Cu, Zn, As, Rb, Sr, Mo, and Cd.  Correlations among the individual elements and between each element with grain shape, plant height, and time of heading were also studied.  

Many of the grain element QTLs were significantly associated with multiple elements, supporting the concept of element networks within plants, and indicating the importance of studying multiple elements at a time. Grain shape, heading time and plant height proved to have much less direct influence on rice grain mineral concentrations than was anticipated.