With the aid of high –tech tools Agricultural Research Service and collaborating scientests are closing in on the genes in rice that regulate the uptake and storage of important minerals – a pursuit that could bolster the nutritional value of the cereal grain crop as a staple food for roughly half of the world’s population.
Ultimately, the team envisions bio fortifying rice using traditional plant breeding methods to develop new varieties whose grains boast exceptionally high concentrations of essential minerals , including zinc, iron, and calcium.
Rice is a mainstay of the human diet for good reason. It is a good source of energy, free of gluten (which causes allergic reactions in some individuals ), easy to digest , low in fat , and packed with vitamins , minerals and other nutrients . Some key elements , however, like iron , are lost when the bran on brown rice is stripped off during milling to produce the so-called white rice , notes Shannon Pinson , a plant geneticist with the ARS Dale Bumpers National Rice Research Center in Stuttgart, Arkansas.
More than 70 percent of the white rice eaten in the United States is enriched, meaning that thiamine, niacin , iron and folic acid have been added to the outside surface of the uncooked white kernels to bring the overall nutritional level up too or higher than that of the whole grain ( brown rice) for these vitamins .But in developing countries where rice is a mainstay, fortifying the grain after milling may not be viable option. Additionally, the soils in which the crop is grown may be lacking in certain essential minerals . For population that rely on rice as a staple food , low level of irons ,zinc or other minerals can lead to nutritional deficiencies that manifest as fatigue , poor immune system function , and other symptoms . Indeed, more than three billion people worldwide suffer from iron or zinc deficiencies in their diets .
To address these concerns , Pinson and her ARS and university colleagues focused their studies on three different groups , or “populations” of rice with the most diverse represented by 1,643 lines called “accessions” collected from 114 countries around the world . In this diverse group, the researchers encountered rice accessions whose grains contained up to nine times the amount of minerals normally observed in standard U.S. varieties .The group began the project in 2007. The National Science Foundation is supporting the effort , which include mapping the
approximate locale of genes on rice’s 12 chromosomes and developing marker data to easily detect them during breeding efforts.
Based on the data from side-by-side comparisons conducted under controlled field conditions in Beaumont, Texas the team identified 40 rice accessions whose grains contained high levels of minerals important not only to human health, but also to that of the rice plant. Take for example, calcium.
Calcium strengthens the plant cell wall and decreases permeability of cell membranes , which in turn , can lead to increased resistance to diseases and environmental stresses.
Also of interest are rice accessions with lo grain levels of certain elements that are toxic to plants and people , such are arsenic and cadmium . Rice with low levels of Arsenic or cadmium may have genes that sequester or bind these toxic minerals in leaves instead of grain or that curtail their absorption from contaminated soil s or irrigated water – a concern, for example in parts of Bangladesh where rice is grown as a staple crop and high arsenic levels in water are indigenous .In the studies , the team compared mineral uptake in rice plants grown in flooded and non flooded fields . Flooding , Pinson explains , changes the soil chemistry and converts some elements into forms more available for mineral uptake .By studying plants grown in both soil conditions , the team were able to identify even more genes function in the plant to affect element uptake and accumulation.
To date, the team has identified 127 genes clustered in 40 different chromosomes regions that correlate to high concentrations of particular minerals .They have also identified genes affecting other grain features, including shape, and found that grain element accumulation is largely dependent of these other grain quality attributes.
Other findings: There is a wide range of mineral concentrations among rice accessions from around the world. Mineral levels fluctuated more when rice was grown in nonflooded fields than in flooded ones .Rice with the highest grain levels of certain minerals like molybdenum (important for plant nitrogen nutrition; high levels help rice cope with acidic soils ). Sometimes originated from the same geographic region of the world. Natural gene variation may be responsible for some of the highest mineral levels in grain..Plant maturity influences the amount of mineral absorbed and where it is stored –in leaves , bran or grain, for example.
In addition to ensuring the consumers get more of the essential minerals needed for their sustained health and well-being , biofortified rice could mean expanded markets , the approach could serve as a useful model for biofortifying other important grains that feed the world.
By: Richelle P. Ponce I T-II I Pagalanggang National High School I Dinalupihan, Bataan
