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United States Department of Agriculture

Agricultural Research Service

Research Project: Attributable Factors to Rice Straighthead and Development of a Natural Screening and Evaluation Site

Location: Dale Bumpers National Rice Research Center

Project Number: 6225-21000-010-24
Project Type: Reimbursable

Start Date: Oct 01, 2012
End Date: Sep 30, 2015

Objective:
Rice is a staple food for over half of the world's population. As a third exporter of rice, the U.S. plays an important role in global food security. The overall goal of this proposed research is to reduce the risk of rice production losses due to straighthead disorder. This is a physiological malady that is associated with anaerobic conditions found in flooded rice fields and can result in complete yield loss in fields where it occurs. It is estimated that about one-third of the rice acreage in Arkansas is drained early in the season as a preventative measure for straighthead. This wastes 151 million m*3 of water in Arkansas annually and results in over $7 million in additional energy costs to re-flood these fields. Developing a better understanding of the soil-plant interactions for straighthead to occur will help establish an economic strategy to stabilize yield, and save water and energy. The specific objectives are to: a) Determine the soil, plant, and environmental factors that impact straighthead disorder in rice germplasm evaluated under a site (UAPB) known to induce straighthead and at another site (DBNRRC) amended with a chemical that induces the symptoms, b) Establish a straighthead evaluation site using natural (non-amended) soils at UAPB for on-going research to support rice breeding efforts in the southern USA, and c) Expand UAPB capacity in agricultural research and education.

Approach:
Task 1: Determine the Genetic Response to Straighthead Induction Using Natural and Chemically Amended Soil Sites Two field testing sites will be used through the course of the project. The UAPB site has been observed to naturally induce straighthead symptoms, whereas the DBNRRC site has been used for many years for straighthead evaluation following amendment with an herbicide (MSMA). One hundred germplasm accessions including domestic and foreign cultivars will be tested in a Randomized Complete Block Design at both sites. Maturity will be measured by date when 50% of panicles emerge from the sheath. At the end of the season, grain yield and plant height will be measured and straighthead symptoms will be scored using a 0 - 9 rating scale as described by Yan et al. (2005). Task 2: Determine Soil and Water Factors Associated with Straighthead Resistance Cultivars that are resistant, intermediate, and susceptible to straighthead from Task 1 will be grown in large plots at both field sites using a Completely Randomized Block Design. Soil and water samples will be collected from each plot every month from planting until harvest. Plant height, grain yield, and straighthead will be recorded at the end of season. Soil samples (0-15 cm) will be characterized for major/minor/trace elements, organic content, texture, pH, and cation exchange capacity using the USDA standard procedures. Water samples will be analyzed for major/minor/trace elements. Task 3: Determine Plant Factors Associated with Straighthead Resistance In the experiment for the Task 2, a main tiller and the most recently emerged (top) two leaves will be collected from each plot every month, and panicle samples will be collected every week from heading to maturity. The elemental (P, K, Ca, Mg, Na, S, Fe, Mn, Zn, Cu, and B) composition in the tissue will be determined using the ICP-AES. Task 4: Identification of Resistant Germplasm for Straighthead Improvement Germplasm accessions that had statistically similar straighthead symptoms in both the sites will be selected from year 1 for verification in large plots in year 2. In year 3, the most resistant germplasm accessions will be tested in farmer fields where straighthead has frequently occurred. Meanwhile, the most resistant accessions will be evaluated for agronomic characteristics in both the sites. The resulting information will be used by breeders for parental selection. Throughout these stages of operation, UAPB undergraduate and graduate students will be trained in scientific methods, experimental design, soil and plant sampling, field operations for rice farming and research, evaluation methods for screening for straighthead resistance, breeding techniques, making scientific presentations, and assisting in manuscript drafting.

Last Modified: 9/1/2014
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