Submitted to: Rice Technical Working Group Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: December 6, 1999
Publication Date: N/A
Technical Abstract: Amylose content is the most important factor determining rice cooking and processing quality. The same variety grown in different environments may vary by up to 6 percent in apparent amylose content. This variation may cause processing problems. A better understanding of the impact of the environment and plant genetics in the control of rice quality parameters would help breeders, producers and industry end-users. A study was conducted using over 200 progeny from a cross of Toro 2 and Rexmont which differ for amylose content, alkali spreading value, and starch pasting properties. Progeny were evaluated over 3 years with the objective of obtaining a better understanding of the heritability and role that specific genes may play in rice quality. The progeny were evaluated for genetic polymorphisms that are associated with the starch biosynthesis enzymes granule bound starch synthase (GBSS), soluble starch synthase (SSS), starch hbranching enzyme 1 and 3, and starch debranching enzyme. The GBSS and SSS genes were the only loci significantly correlated with amylose content and starch pasting properties. Since both genes are located at one end of chromosome 6, a path coefficients analysis was used to determine that the GBSS gene had a major impact on amylose content, breakdown viscosity, and setback viscosity while SSS had a relatively minor impact. SSS which plays a major role in the synthesis of amylopectin, apparently has a significantly smaller role in the control of starch pasting characteristics when compared with GBSS. Additional results on the heritability of amylose content, alkali spreading value, and starch pasting properties in this cross were also determined.