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Report on U.S. rice quality reveals concerns, points to solutions

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Unreleased report looks at U.S. rice quality concerns.

A comprehensive report on U.S. rice quality, touted while being written, has still not been officially released to the public despite its completion in 2012. However, Farm Press has secured a copy and the report’s findings are in line with what rice specialists around the Mid-South have been saying for years.

For more on rice quality, see here, here and here.

Titled “Report to the USA Rice Federation Rice Marketability and Competiveness Task Force/Quality Assessment of Rice Samples Produced in 2012,” the summary says the nine-page report is the culmination of three surveys to “assess grain quality in (the United States) and imported long grain sources.”

The objectives of the study:

  • Determine the grain quality differences of 16 southern U.S. inbred cultivars and 3 hybrids grown in a side by side study at 6 mid-south locations.
  • Evaluate the impact of optimum and delayed planting dates on grain quality parameters.
  • Compare these southern produced samples with one California long grain produced at two plant dates in California and imported milled samples from Thailand and Uruguay.
  • Assess consistency and relationship of subjective Mill scores and objective laboratory measures.
  • Associate weather data and agronomic traits with grain quality.

The results of this study demonstrated that:

  • The U.S. does have cultivars that have high Mill score values and low chalk like high quality imported samples, however these cultivars are not the most predominantly grown. Some of the more widely grown cultivars, have lower Mill scores and higher chalk. These results suggest that breeders have access to genetic materials that can serve as the basis for on-going breeding improvements in U.S. long grain rice quality.
  • Although cultivars differ in grain quality traits, growing environment was the major factor impacting whole milling yield. Whole milling yield was improved with earlier planting dates, lower heat units during grainfill, and ensuring uniform drying of samples prior to milling. These results indicate that optimizing the production environment and post-harvest handling are necessary to maintain high milling yields.
  • Different methods of determining chalk were utilized. Although the amount of chalk differed greatly depending on the method used, the methods were moderately correlated with each other.
  • As observed in other studies, some Mills evaluate samples quite differently than others. In addition, some Mills have greater repeatability in assessment of subjective traits.

Conclusions:

“This study was conducted to evaluate a set of U.S. rice cultivars grown in side-by-side field trials for both subjective and objective quality traits. The goal was to determine how U.S. cultivars compare to high quality imports and to learn more about the relationship between subjective and objective assessments of quality. In addition, agronomic and weather data from each production site allowed analysis of how these factors may impact quality. This study demonstrated that the different estimates of chalk as determined by Winseedle and S21 Image analysis system and by Russell Marine (graders for export market) differed widely in the amount of chalk. The Winseedle system was calibrated to score much lower levels of chalk than the S21 system or that as subjectively determined by Russell Marine. However, all three methods tracked chalk variability in a similar manner, although the scale was much different. Correlations among the Winseedle, S21, Russell Marine, and the Mill method demonstrated that the Winseedle method was generally more highly correlated with all other methods and was more precise.” “Ten commercial Mills participated in evaluation of 226 rice samples using established criteria for 5 subjective traits. As in previous studies, there was significant variability in how the Mills scored the same samples. Some Mills scored samples more favorably while others were less favorable. In this study, Mills were provided with a repeated check of a sample that was presented at random to them 13 times. Results from this assessment of the repeated check demonstrated that there was significant variation for some Mills in how a sample was scored, as would be expected in subjective assessment. This suggests that identifying baseline standards that all Mills would agree to may help the research community to better meet their goals for quality.

“Nineteen southern U.S. long grains were grown at different locations and planting dates for a total of 11 production environments in the Southern U.S. Results demonstrated that location accounted for the biggest difference in whole milling yield of samples. The Stuttgart location was characterized as the hottest in 2012, while the Beaumont location had the poorest milling yields and Mill assessments of quality. The NE Ark and Stuttgart locations had a relatively positive impact on milling yield as compared to Missouri, Stoneville, Crowley, and Beaumont. In addition, careful post-harvest handling to dry samples to a uniform moisture also enhanced milling quality.

“Two planting dates, optimum and delayed, were compared. The delayed planting date was associated with higher growing degree days, faster plant growth cycles reaching heading and maturity earlier, decreased milling yields, less favorable Total score by Mills, larger grain dimensions, and greater chalk. Thus, planting earlier in 2012, enhanced milling and grain quality.

“The imported, commercially milled, samples from Thailand and Uruguay were ranked high by the Mills and had low chalk. U.S. cultivars that were similar to the imported samples according to Mill scores and estimates of chalk were Presidio and Cheniere grown in the Mid-south and L206 grown in California. Thus, the U.S. does have cultivars that can compete with high quality samples from other regions of the world in the export market if evaluated on a variety basis (not blended).

“However, some of the most predominantly grown cultivars in the southern U.S. were found to be ranked low for Total Mill scores and high for chalk. Thus, the cultivars with the highest yield and commercial acceptance may not have the highest quality. However, the results show that breeders have access to genetic resources with high milling quality and low chalk that can be used in on-going breeding efforts to improve these traits. New technology like the image analysis scanners for grain dimensions and quantifying chalk will be helpful in objectively selecting for these traits.”

Read the full report here.

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