Gelatinization properties of starches from three successive generations of six exotic corn lines grown in two locations

The objectives of this research were to evaluate the intra- and interpopulation variability in gelatinization properties of starches from exotic corn lines and their derivatives when grown 1) during two successive years in the same location; and 2) in both temperate and tropical environments. Six novel exotic corn lines (two 100% exotic and four 25% exotic derived from a breeding cross developed by crossing an exotic hybrid with Corn Belt lines) were selected for this research because their starches have significantly different (and potentially useful) thermal properties from those found in starch from normal Corn Belt corn. The S(n) (n = 3 for 25% exotic lines and n = 1 for 100% exotic lines) generations of the six exotic lines were self-pollinated and grown in the winter nursery in Puerto Rico. Two successive generations (S(n+1) and S(n+2)) of lines selected for low onset of gelatinization temperature were self-pollinated and grown in the same environment near Ames, IA. To evaluate the effect of environment, the S(n+2) generation also was self-pollinated and grown in the winter nursery in Puerto Rico. Thermal properties of starches from 10 single kernels from each line were analyzed by using differential scanning calorimetry (DSC) at a ratio of 4 mg of dry starch to 8 mg of distilled water. After subsequent generations, the differences in DSC gelatinization properties between selected kernels within each progeny line narrowed, suggesting increased homogeneity of starch structural properties within each line. Unusual thermal properties were fixed in some progeny lines. Environmental factors also affected the thermal properties of starch and a significant interaction between environment and genotype was observed. These results suggest that introgression of adapted germplasm with useful genes from exotic corn would increase the available genetic variability for starch functionality and allow the development of hybrids with important value-added traits.