Title: Diversity for concentrations of mineral nutrients and trace elements in rice grains Authors
|Tarpley, Lee -|
|Zhang, Min -|
|Geurinot, Mary Lou -|
|Salt, David -|
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 21, 2014
Publication Date: June 20, 2014
Citation: Pinson, S.R., Tarpley, L., Yan, W., Yeater, K.M., Zhang, M., Geurinot, M., Salt, D.E. 2014. Diversity for concentrations of mineral nutrients and trace elements in rice grains. Crop Science. doi:10.2135/cropsci2013.10.0656. Interpretive Summary: For people who rely on rice as their dietary staple, a large proportion of their micronutrients come from rice grains. Some of these nutrients are essential (e.g., zinc) while others are unwanted (e.g., arsenic). The identification of rice genotypes containing unique concentrations of the various mineral elements is an important first step toward breeding new rice varieties with enhanced grain nutritional value (known as biofortification), and can be used as well to identify the genes and mechanisms the plants are using to move (or block the movement of) the elements from the soil into their edible grains. In this study of 1763 rice accessions from around the world, accessions exceptionally high in grain concentration of particular elements were rare. However for those identified, it appears likely that their increased element concentration may be due to a change in a single gene, which would be easier for breeders to incorporate into new varieties than a complex multi-gene controlled trait. Furthermore, because of genetic similarity between rice and other cereal crops, new knowledge generated on the genes and mechanisms determining the nutritional value of rice can also be used to enhance the nutritional value of other grains, such as wheat, oats, and barley. This study identified a number of rice accessions with unique grain element concentrations that we have since crossed with a U.S. cultivar in order to start identifying the underlying genes and physiological mechanisms that control element accumulation.
Technical Abstract: With the aim of identifying rice (Oryza spp.) germplasm having enhanced grain nutritional value, the mineral nutrient and trace element content (a.k.a. ionome) of whole (unmilled) grains from a set of 1763 rice accessions of diverse geographic and genetic origin were evaluated. Seed for analysis of total concentration of the elements P, Mg, K, S, Ca, As, Cd, Co, Cu, Fe, Mn, Mo, Ni, Rb, Sr, Zn by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) was produced over two years in Beaumont, Texas, under both flooded and unflooded watering regimes. The distribution of all elements analyzed were skewed toward low grain concentrations. A significant portion of the ionomic variation observed has a genetic basis (broad sense heritabilities 0.14 - 0.75), indicating an ability to breed for improved grain concentration of all elements except nickel. Variation in grain elemental concentrations was not strongly associated with plant height, heading time, or grain shape, suggesting that mechanisms other than these are of primary importance in controlling ionomic variation in rice grain. Accessions high in specific elements were sometimes found to have similar genetic or geographic origins, suggesting they share a heritable mechanism underlying their enhanced ionomes. For example, accessions enhanced for Ca, Mg, or K were more common in the indica than the japonica subgroup; low As was most common among temperate japonica accessions; and several lines high in Mo originated in Malaysia or nearby Brunei.