Genetic modifiers of maize (Zea mays L.) starch thermal properties were examined by differential scanning calorimetry (DSC). Sugary- 2 (su2) kernels from segregating ears were identified based on textural appearance of starches following crosses between an exotic maize accession with the inbred OH43 homozygous for the su2 allele (OH43 su2). Two exotic maize accessions, PI213768 and PI451692, were used. Germs retained from su2 kernels were used to produce an F2 population of su2 plants containing 50% exotic germ plasm. With few exceptions, F2 ears from the populations were homozygous for the su2 allele. Significant (P less than or equal to 0.05) differences were seen between the exotic populations and OH43 su2 for gelatinization onset temperature (To), range (RN), enthalpy (deltaH), and retrogradation (%R). The number of DSC values with significant within-population variations was greater among F2 ears within the exotic populations than among ears within the inbred line OH43 su2. Standard deviations for DSC values were consistently greater for exotic su2 populations than for those of OH43 su2. Also, the population PI213768 su2 differed greatly from OH43 su2 for mean values of To, RN, deltaH, and %R (52.8 C, 13.4 C, 1.5 cal/g, and 34.5%, respectively) when compared to those of OH43 su2 (54.6 C, 10.6 C, 1.3 cal/g, and 29%, respectively). Results from this study indicate that examining the texture of starches from single kernels may be used to identify and develop populations homozygous for the su2 allele. In addition, the increased variability for DSC values within populations containing 50% exotic germ plasm suggest that genetic modifiers might be used to alter thermal properties and, possibly, functional properties of su2 starch.
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