Frequency of euploids in different seed size classes of hexaploid triticale

Summary Bulk seeds of each of nine strains of hexaploid triticale were classified according to size by passing them over four round-holed sieves, 8/64, 9/64, 10/64 and 11/64-inch mesh. The actual size was different in different strains depending on the characteristic seed size of the strain (Table 2). Of the nine strains, six had low aneuploid frequency (11.8% average) and three had high aneuploid frequency (39.0% average) in the bulk populations. Chromosome numbers were counted in root-tip mitosis of germinating seeds.The frequency of euploids was highest in large-seed classes in all but one strain, UM 6608 (Group F). The euploid frequency was variable in medium- and small-seed classes. It was suggested that the screening of larger seeds would give a higher frequency of euploids, particularly in most populations with a low frequency of aneuploids.