EFFECTS OF POLLINATION METHOD AND GROWING LOCATION ON STARCH THERMAL-PROPERTIES OF CORN HYBRIDS

Starch gelatinization and retrogradation properties of corn were studi ed to determine the effect of controlled (self) pollination versus non controlled pollination on analytical determinations, and the potential to eliminate the expensive and time-consuming step of self-pollinatin g before research screening of corn genotypes. Twenty-four hybrids wer e grown in two Iowa locations, Story City and Ames. At Story City, all hybrids received three pollination treatments: self-pollination; smal l-plot, open-pollination (representing corn from small test plots); an d large-plot, open-pollination (representing corn from a farmer's fiel d). Self-pollinated and small-plot, open-pollinated corn were grown in replicated two-row plots, whereas large-plot, open-pollinated corn wa s grown in unreplicated plots of 12.8 m x 8 rows. At Ames, the small-p lot, open pollination treatment was not done. Starch was extracted fro m samples of corn harvested from each plot, and gelatinization and ret rogradation properties were determined using differential-scanning cal orimetry (DSC). Hybrids exhibited different starch gelatinization and retrogradation properties. Significant differences (P less than or equ al to 0.05) in starch gelatinization and retrogradation properties occ urred among pollination methods and between locations. Pollination met hod did not influence gelatinization enthalpy values, but onset temper ature values for gelatinization, and range values for retrogradation d iffered significantly among pollination methods. At Ames, treatments g ave different values for retrogradation enthalpy and percentage of ret rogradation. Because of differences in some starch characteristics ass ociated with pollination methods, self-pollination is recommended when growing samples in small plots for research purposes.