Misdivision of Homoeologous Group 5 Univalent Chromosomes in Hexaploid Wheat

II. Univalents derived from American and European cultivars

Abstract

Misdivision rates of wheat chromosomes 5A, 5B and 5D were determined at meiotic anaphase I in F1 monosomic plants from crosses between the group 5 monosomics of Chinese Spring and ten American (U.S.), one South American, and eleven European cultivars. The misdivision rate was usually higher for one chromatid than for both chromatids of each group 5 univalent, but in 5B from the cultivar Seneca, misdivisions involving both chromatids were three times higher than those involving one chromatid. Significant differences in misdivision rates occurred between the European (including the South American cultivar) and American groups, and also among cultivars and chromosomes within each group. 5A and 5B had similar misdivision rates, which were generally higher than those for 5D. 5A of Chinese Spring in its own background had the highest misdivision rate of any group 5 chromosome or cultivar source. The European and American groups had similar ratios of bipolar versus unipolar distributions of normally divided or misdivided chromatids. The behavior of group 5 chromosomes was compared in these two groups and in a Japanese group reported in a companion paper. Misdivision rates seemed to be affected by the specific chromosome, the genetic background in which it occurred, and possibly environmental conditions.