Misdivision of Homoeologous Group 5 Univalent Chromosomes in Hexaploid Wheat

I. Univalents derived from Japanese cultivars

Abstract

Misdivision rates of wheat chromosomes 5A, 5B, and 5D were determined at anaphase I of meiosis in F₁ monosomic plants from crosses between Chinese Spring monosomics as female parents and ten Japanese local cultivars. The average misdivision frequencies were 15.3% for 5A, 10.5% for 5B, and 8.4% for 5D. The frequencies of unipolar distributions of monosomes or their derivatives were 31.7%, 34.7%, and 18.1% for 5A, 5B, and 5D, respectively. Although there was a large error variance, the differences among chromosomes and the chromosome-cultivar interactions were significant for both misdivision rates and unipolar distributions, but there were no significant differences among cultivars. The correlation (r=.554) between the frequency of misdivision in cells with bipolar distributions and the frequency of cells with unipolar distributions suggested that these traits were affected by common genetic and/or environmental factors. The female transmission of the group 5 monosomes and their derivatives averaged 12.2% for Chinese Spring. Of the transmitted monosomes, 6.9% were telocentric chromosomes, 3.4% isochromosomes, and 89.7% normal chromosomes. When the Chinese Spring monosomics were crossed with three Japanese cultivars, the transmission frequency to the F₂ of the monosomes from the Japanese cultivars averaged 30%, with 9.2%. telocentric and 90.8% normal chromosomes. These results were compared with expected transmission frequencies of the monosomes and their derivatives.