29 Analysis of waxy proteins of wheat and oats: Applications in breeding.

R. A. GRAYBOSCH (1), and J. Skerritt. (3) USDA, ARS, University of Nebraska, Lincoln, NE, USA, (2) CSIRO Plant Industry, Canberra, Australia.

Waxy proteins, also known as the granule-bound starch synthase (GBSS), are responsible for the synthesis of amylose in developing endosperm cells. In hexaploid bread wheats, genes found on chromosomes 7A, 7D and 4A encode three isoforms of GBSS. Modified SDS-PAGE procedures have allowed the separation of these three isoforms, and the identification of null alleles, or genes that do not result in a detectable gene product. Through breeding, lines carrying various null alleles have been combined to develop both amylose-free (waxy) and reduced-amylose bread and durum wheats. Monoclonal antibodies raised against GBSS have been used to develop an ELISA protocol that can identify both waxy and reduced-amylose genotypes. Protein analytical techniques, rather than direct measurement of amylose, have proven a more precise tool in the identification of GBSS genotypes. Manipulation of the number of active GBSS-encoding genes has allowed the development of wheats with a range of amylose contents and starch pasting properties. Extension of the techniques developed in wheat to oats, another hexaploid crop, has demonstrated the existence of a similar gene system. The potential for the development of waxy and reduced amylose oats will be discussed.