Isolation and characterization of euplasmic wheat-barley chromosome addition lines

SummaryHybridization of Chinese Spring wheat and Betzes barley using wheat as the female parent gave only 1·3 per cent seed set compared to 15·4 per cent obtained with the reciprocal cross made earlier. Furthermore, only one of the 20 F1 hybrids obtained possessed the normal complement of 28 chromosomes. The others had unusual chromosome numbers ranging from 21-36 in different plants. The 28-chromosome normal hybrid was backcrossed to wheat to produce a heptaploid in the first backcross generation (BC1) and subsequently monosomic (21 II + 1 I) and double monosomic (21 II + 1 I + 1 I) additions of barley chromosomes to wheat were isolated in the BC2 generation. The monosomic additions could be divided into five different phenotypic groups and disomic additions were isolated from among their progeny with a very low frequency (0·63 per cent). However, some monotelo-disomic additions (21 II +1t II) obtained from the progeny of selfed monosomies yielded both disomic and ditelosomic additions in their progeny with a much higher frequency. A sixth addition line was obtained independently from three unusual F1 hybrids exhibiting 22 I, 21 I + 1 II and 25 I + 1 III at meiosis.Altogether six of the seven possible disomic additions and seven of the 14 ditelosomic additions of barley chromosomes to wheat have been produced. The chromosome 5 addition could not be obtained in a disomic form because the plants carrying this chromosome are self-sterile. The addition lines were initially characterized by their morphological differences from the wheat parent, and subsequently from isozyme studies and heterochromatic banding (N-banding) of chromosomes. Most of these lines showed more asynapsis at meiosis than the wheat parent and all, except addition line 4, were less fertile than the wheat parent.