Characterization of waxy grain sorghum lines in relation to granule-bound starch synthase

Authors

J. F. Pedersen, USDA, ARS, NPA Wheat, Sorghum and Forage ResearchFollow
S. R. Bean, USDA, ARS, NPA, GMPRC
R. A. Graybosch, USDA, ARS, NPA Wheat, Sorghum and Forage ResearchFollow
S. H. Park, Kansas State University, Manhattan, Kansas
M. Tilley, USDA, ARS, NPA, GMPRC

Date of this Version

9-13-2005

Comments

Published in Euphytica (2005) 144: 151–156.

Abstract

The waxy phenotype, associated with endosperm containing little or no amylose, has been recognized in sorghum (Sorghum bicolor L. Moench) since 1933. Although variants of the waxy gene are well characterized in other cereals, the waxy trait has been assumed to be controlled by a single allele, wx, in sorghum. Recent improvements in technologies encourage re-examination of the waxy sorghums. The objectives of this research were therefore to identify and characterize sorghum lines with differing waxy alleles and to describe the actions of those alleles in crosses. Grain of eight waxy sorghum lines (BTxARG1, BTx630, Tx2907, B.9307, 94C274, 94C278, 94C289, 94C369), three wild-type checks (BWheatland, RTx430, BN122), and F₂ families from crosses among a subset of these lines were evaluated for presence or absence of granule-bound starch synthase (GBSS), the gene product of the wx locus, and wild-type vs. waxy endosperm. The F₂ segregation ratios were tested for fit to a 3:1 ratio using Chi-square analyses. Two distinctly different naturally occurring waxy alleles were identified: One with no GBSS (GBSS−), and one with apparently inactive GBSS present (GBSS+). We propose that the waxy allele with no GBSS be designated wxa, and that waxy allele with apparently inactive GBSS present be designated wx^b. These two alleles are located in close proximity on the waxy locus. The wx^b allele is dominant to the wx ^a allele in terms of GBSS production, and both are recessive to the wild-type W ^x in terms of amylose content.