Submitted to: Plant and Animal Genome Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: August 1, 2003
Publication Date: December 10, 2003
Citation: Chen, M., Bergman, C.J., Fjellstrom, R.G. 2003. Genetic variation at the waxy locus associated with starch pasting properties in international rice germplasm. In: Proceedings of the Plant and Animal Genome Conference Proceedings. p. 168. Technical Abstract: Rice starch pasting properties are used to characterize the processing and cooking qualities of rice (Oryza sativa L.). The Waxy gene on rice chromosome 6 encodes the granule-bound starch synthase enzyme, which controls much of the variation in grain amylose content, and reportedly has major effects on starch pasting properties. Amylose content, however, does not explain all the variation in rice pasting characteristics. Some varieties with similar apparent amylose content have very different pasting viscosities. We are studying 164 diverse rice accessions with apparent amylose contents ranging from 0 to 27%, and determining sequence variation in the Waxy gene to identify associations between pasting properties and genotypes. Rexmont, a javanica type rice with a strong pasting curve, has a characteristic single nucleotide substitution resulting in an amino acid change in exon 10 of the Waxy gene. Accessions that have the Rexmont mutation in exon 10 (all with high apparent amylose) consistently display a strong RVA curve, with significantly different (pless than 0.0001) hot paste viscosity, cool paste viscosity and setback from those with a weak RVA curve (apparent amylose contents ranging from 0 ' 27%). Within the 42 high amylose accessions, this single nucleotide polymorphism explains 71%, 83%, 78%, and 53% of the variations in peak viscosity, hot paste viscosity, cool paste viscosity, and setback, respectively. The high amylose accessions with a strong RVA curve (Rexmont type) all have a Waxy CT 11 repeat, while the ones with weak RVA curve (Jodon type) have 8, 10, and 20 CT repeats.