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Rapid Screening to Identify Unusual Thermal Starch Traits from Bulked Corn Kernels

¹Graduate student and professor, respectively, 2312 Food Sciences Building, Department of Food Science and Human Nutrition and Center for Crops Utilization Research, Iowa State University, Ames, IA 50011. ²Currently, Food technologist, Tate and Lyle North America, Decatur, IL 62525. ³Biologist, USDA-ARS, Plant Introduction Research Unit, Department of Agronomy, Iowa State University, Ames, IA 50011. ⁴Corresponding author. Phone: 515-294-9688. Fax: 515-294-8181. E-mail: pjwhite@iastate.edu

Differential scanning calorimetry (DSC) is used routinely to screen for starch thermal properties. In early generations of line development, the established analysis separately evaluates starch extracted from five, single corn kernels. A thermal property trait carried by a recessive gene would appear 25% of the time; thus, if five separate kernels were evaluated, the likelihood of detecting an unusual thermal trait is high. The objective of the current work was to expedite selection by examining five kernels at a time, instead of one, hypothesizing that we would be able to detect different thermal properties in this blend. Corn lines, all from the same genetic background (ExSeed68 or Oh43), with known thermal functions (amylose-extender, dull, sugary-1, sugary-2, and waxy) were blended with normal starch (control) in ratios of 0:5, 1:4, 2:3, 3:2, 4:1, and 5:0, and analyzed with DSC. The values for each ratio within a mutant type were unique (α < 0.01) for most DSC measurements, especially for gelatinization onset temperature, change in enthalpy of gelatinization, and range of gelatinization. These results support the five-kernel method for rapidly screening large amounts of corn germplasm to identify kernels with unusual starch traits.