Identification and characterization of U.S. wheats carrying null alleles at the wx loci
1998
Graybosch, R.A. | Peterson, C.J. | Hansen, L.E. | Rahman, S. | Hill, A. | Skerritt, J.H.
Granule-bound starch synthase (GBSS) is the primary enzyme responsible for the s ynthesis of amylose in amyloplasts of cereal endosperm cells. Bread wheats, due to their hexaploid genetic system, carry three genes (wx loci) encoding GBSS. Pu rification and separation of GBSS from more than 200 North American hexaploid wh eats allowed the identification of genotypes that carry null alleles at either t he wx-A1 and wx-B1 loci. In addition, the cultivar Ike carried both wx-A1 and wx -B1 null alleles. No wx-D1 nulls were detected. Null alleles were found in 10% o f the hard winter wheats tested, but in only 2% of the sampled soft winter wheat s. Amylose contents of wheats carrying single null alleles at either the wx-A1 o r wx-B1 loci often were lower than those of wild type wheats, but greater reduct ion in amylose content was observed in Ike. Monoclonal antibodies were used to q uantify water-extractable GBSS in both wild-type and null genotypes. Gene dosage compensation was evident, although GBSS content, as measured by ELISA, was sign ificantly lower in Ike than in all other wheats. The identification of null alle les in adpated genotypes suggests the development of wheats with a wide range of amylose contents will be possible by simple genetic crossing and selection.
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