II.16 Confirmation of double trisomics by protein electrophoresis.
Robert G. McDaniel. Department of Plant Sciences, The University of Arizona, Tucson, Arizona 85721, USA.
Double trisomics have been obtained from the progeny of partially sterile barley (presumptive triploids), and have been identified cytologically and morphologically (1). Frequencies with which specific chromosomes were associated in double trisomics varied, chromosome 4 and chromosome 6 being found most frequently, comprising 28 and 24 percent, respectively, of double trisomic combinations (2).
Proteins obtained from the germ of individual seeds of double trisomic progenies were characterized by polyacrylamide gel electrophoresis. Double trisomics having different trisomic chromosomes could be distinguished on the basis of the distinctive protein patterns of the specific primary trisomics in their progeny.
In Figure 1, electrophoretic separations of proteins from individual seeds of double trisomic progeny are shown. In this example, chromosome 6 and chromosome 4 are present in three doses. Comparison of the protein patterns, both quantitatively and qualitatively, with those produced by seed of known primary trisomics allows identification of the two chromosomes involved in the double trisomic (3). Matching of protein patterns has successfully identified a number of double trisomics. Double trisomics involving chromosome 4 are the most easily identifiable, as endosperm proteins can also be used to show presence of an extra chromosome 4.
Double trisomics are also found occasionally in double trisomic progeny. These can be distinguished from primary trisomics using protein electrophoresis, but, because of the greater number of changes elicited in protein phenotypes, the chromosomes involved in the double trisomic are identified with less certainty. A double trisomic for chromosome 4 and chromosome 6 is illustrated in Figure 1. An enzymatic assay using isoenzyme separations, or a method wherein pH, gel pore size, or other factors are altered could be developed to identify double trisomic seed if one is desired. Present electrophoretic conditions allow the accurate, rapid identification of double trisomics based on analysis of primary trisomic progeny.
References:
1. Vering, B., 1971. Double trisomics in Betzes barley. Barley Genetics
Newsletter 1: 66.
2. Vering, B. A., 1972. Double trisomics in Betzes barley. Ph.D. dissertation,
The University of Arizona.
3. McDaniel, R. G., and R. T. Ramage, 1970. Genetics of a primary trisomic
series in barley: Identification by protein electrophoresis. Canad. J.
of Genet. Cytol. 12: 490-495.
