Submitted to: Texas Experiment Station Field Day Handout
Publication Type: Experiment Station
Publication Acceptance Date: 6/20/2014
Publication Date: 6/24/2014
Citation: Tarpley, L., Chittoori, R., Pinson, S.R., Salt, D.E. 2014. Rice lines with high leaf mineral nutrient levels. Texas Experiment Station Field Day Handout. Texas Rice, Highlights in Research Special Edition:pg.9-10. http://beaumont.tamu.edu/eLibrary/Newsletter/2014_Highlights_in_Research.pdf Interpretive Summary: While fertilizers have long been used to affect plant chemistry by affecting mineral availability, this study shows that genes also play a very important role in controlling plant chemistry, likely by affecting the rates at which various minerals are taken up by roots, and later transported through the plants’ xylem and phloem. This in turn means that it should prove possible for breeders to develop varieties that will be healthy under variable soil fertility conditions by selecting for genes that improve mineral uptake and internal chemical balances. We have been studying the grain and leaf concentrations of 16 elements in a large, diverse set of rice cultivars that originated from around the world, and is known as the USDA Core Collection. From this set of rice accessions, we have identified some with unusually high concentrations of some of the elements. Of particular interest to U.S. rice producers are those rice cultivars that were found to contain high concentrations of elements that are often required as fertilizer amendments, such as phosphorus, potassium, and zinc.
Technical Abstract: Phosphorus (P) and Potassium (K), and sometimes other mineral nutrients are often applied as fertilizer, in addition to Nitrogen, to help achieve high yields in Texas rice production. For some mineral nutrients, total levels in soil would be sufficient to support the desired rice crop growth, but the nutrients are not in a form that is readily accessible by the plant. To save on fertilizer costs, a potential option is to use varieties that can better exploit the mineral nutrients already present in the soil. This could decrease the frequency and/or amount of fertilizer applied. High leaf levels of a mineral nutrient indicate the ability to take up the nutrient from the soil and transfer it to the vegetation where it can assist in the plant’s physiology. Various micronutrients can sometimes be limiting depending largely on soil conditions. However, high grain levels of mineral nutrients can sometimes promote seedling vigor by providing higher levels of necessary nutrients (as opposed to supplementing soil levels using fertilizer amendments). Dr. Tarpley in The Plant Physiology project in collaboration with Dr. Shannon Pinson (USDA ARS) and Ratnaprabha Chittoori (now at Boise State University) have been systematically screening a diverse collection of rice lines (the USDA Core Collection) for mineral element properties. The screening has been performed at the Texas A&M AgriLife Research Center at Beaumont under flooded and unflooded conditions over the last seven years. Of interest to the Texas rice industry is the fact that several lines with enhanced leaf and/or grain levels of several elements have been identified. For example, several lines accumulating 1.4X more leaf and grain P than a standard US. rice variety used as a check in these studies has been found. Phosphorus is important in all aspects of plant metabolism, especially in energy metabolism and root growth; P is also a key structural component of DNA and other compounds, and it has been shown that seeds low in P produce weak seedlings. Potassium (K) is needed by plants for growth of new buds, maintaining tissue water balance, and for photosynthesis and subsequent transfer of the photosynthate to other parts of the plant. We identified rice lines that accumulate 1.5X leaf K compared to the U.S. check variety, and also provide high grain K. One of the high leaf K lines also has high leaf P. Zinc (Zn) is essential in detoxification metabolism, as well as carbohydrate and nitrogen metabolism. Zinc is frequently added as a rice seed treatment to enhance seedling vigor. Rice lines have been identified that accumulate 2X leaf Zn compared to the U.S. check variety, and also have high grain Zn. The progress toward identifying the DNA markers that can then be used for efficient marker-assisted breeding to develop varieties enhanced for these mineral nutrient levels varies greatly from mineral to mineral. Results from this research may allow decreased fertilizer use and increased sustainability in Texas rice production. Improvement of leaf/grain levels of micronutrients can potentially provide rice varieties that remain healthier under variable soil fertility conditions.