The effect of the Waxy locus (Granule Bound Starch Synthase) on pasting curve characteristics in specialty rices (Oryza sativa L.)

Starch structure and functionality have a significant impact on the utilization of cereal grains as food and feed. Starch viscosity characteristics are used to characterize rice cooking, processing and eating quality. In order to examine the genetics of viscosity characteristics, we developed molecular markers for five of the major enzymes involved in starch synthesis in the endosperm: granule bound starch synthase, soluble starch synthase, rice branching enzymes 1 and 3 and starch debranching enzyme. These markers were polymorphic in a cross between specialty rice varieties of diverging amylose content and viscosity characteristics. Our results indicate that the Waxy locus, encoding the gene for granule bound starch synthase, has a significant effect on peak viscosity, hot paste viscosity, cool paste viscosity, breakdown and setback viscosity. We estimate that the tightly linked (5-10 cm) locus for starch synthase may have a lesser, additive effect.