2001 AACC Annual Meeting Charlotte, North Carolina October 14-18, 2001 Charlotte Convention Center

The enzyme granule-bound starch synthase (GBSS) is responsible for amylose synthesis in the endosperm of cereals. Oat (Avena sativa), an allohexaploid species, contains multiple genes encoding GBSS. Using 1 dimensional SDS-PAGE, several isoforms of oat GBSS were detected. A survey of germplasm ancestral to the North American oat gene pool revealed 8 different GBSS phenotypic groups, based on the number (range was 1-3) and forms of GBSS present. An experiment was conducted to determine whether these different GBSS combinations had effects on oat starch properties. Forty cultivars, representing these 8 different phenotypic groups, were grown together under irrigation in Yuma, Arizona. Starch properties were investigated by use of the Rapid Viscoanalyser (RVA) and differential scanning calorimetry (DSC). Significant differences among the oat cultivars were detected for all RVA variables, including peak and final viscosities, and peak temperatures. Starch paste peak viscosities ranged from a low of 150 RV units in the cultivar 'Brooks' to a high of 320 RV units in cv. 'Orbit'. DSC revealed significant variation in the onset temperatures, and transition enthalpies of two endothermic peaks. Variation in starch pasting properties was significantly correlated with variation in the second endothermic peak, or the peak corresponding to the amylose-lipid complex. Observed differences were not, however, a function of the GBSS phenotypic groups, but might reflect subtle differences among the tested genetic backgrounds in amylose content or some other aspect of starch structure.