II. 30. Half-seed determination of hordeins associated with known Ml-a alleles conferring race-specific resistance to barley powdery mildew.
C. T. Hash, Jr. and T. K. Blake, Department of Agronomy and Soils, Washington State University, Pullman, Washington 99164, U.S.A.
Jensen et al. (1980) reported the tight linkage in barley of the hordein loci Horl and Hor2 with the powdery mildew resistance locus Ml-a. The order of the loci is Horl, Ml-a, and Hor2, with Horl being nearest the centromere. Shewry et al. (1980) agreed with this ordering of these loci and further suggested that this tight linkage might be exploited by plant breeders attempting to improve resistance of barley varieties to powdery mildew (Erysiphe graminis f. sp. hordei).
The study reported here was designed to determine the hordein-l and hordein-2 electrophoretic banding patterns of a number of barley varieties carrying identified Ml-a alleles and of the variety 'Advance', an adapted variety which is susceptible to powdery mildew.
Seed of the resistant lines was obtained from the USDA World Barley Collection at Beltsville, Maryland. Half-seed hordein samples were prepared by the method of Blake (1981). Hordein samples were subjected to SDS polyacrylamide gel electrophoresis (Laemmli, 1970) on an 8 to 16T acrylamide linear gradient gel at 15 m Amps per gel for three hours. Visualization of the hordein banding patterns was accomplished using a Coomassie Brilliant Blue R-250 protein stain followed by 10% TCA destain.
All varieties examined here exhibit hordein banding patterns which are
distinctly different from those of Advance (see Figure 1). Therefore, selection
of F2 and/or backcross seeds carrying these known Ml-a alleles should
be possible by the SDS PAGE half-seed technique outlined here. Development
of an Advance multiline variety composed of isolines differing essentially
only in their Ml-a alleles for powdery mildew resistance and their
Horl/Hor2 alleles appears to be feasible. The different hordeins
in the different components of the multiline would aid in identification
of these individual components.
Figure 1. Drawings of hordein electrophoretic banding patterns with apparent molecular weight estimates determined using Phosphorylase b, Bovine Serum Albumin, Ovalbumin and Carbonic AnEydrase as standards. Sample sources and resistance types: 1) Rogers, Ml-a7; 2) Oliveres Litoral, Ml-a11; 3) Maris Mink, Ml-as; 4) I 25, Ml-a*; 5) I 5, Ml-a9; 6) CM 72, Ml-a*; 7) Advance. * resistance type unknown
Most of the resistant varieties utilized in this study originated on the Indian subcontinent and most of these have very similar hordein-2 electrophoretic banding patterns. This may indicate that these varieties and the Ml-a alleles they carry (Ml-a5, Ml-a7, Ml-a9, Ml-a10 , Ml-a11l, and Ml-a? --the latter being present in 'Oliveres Litoral', derived from 'Engledow India') are closely related and may have arisen from a common progenitor.
References:
Blake, T. K. 1981. New techniques for evaluating lysine content in hordeins. Barley Genetics Newsletter 11:79-83.
Jensen, J., J. H. Jørgensen, H. P. Jensen, H. Giese and H. Doll. 1980. Linkage of the hordein loci Horl and Hor2 with the powdery mildew resistance loci Ml-k and Ml-a on barley chromosome 5. Theor. Appl. Genet. 58:27-31.
Laemmli, U. K. 1970. Cleavage of structural proteins during the assembly of the head of bacteriophage T4. Nature 227:680-685.
Shewry, P. R., A. J. Faulks, R. A. Pickering, I. T. Jones, R. A. Finch and B. J. Miflin. 1980. The genetic analysis of barley storage proteins. Heredity 44:383-389.
