| Analysis of chromosome pairing in interspecific and
intergeneric F1 hybrids involving hexaploid Aegilops crassa
J. H. MELNYK and R. C. MCGINNIS Children's Hospital Winnipeg, and Department of Plant Science, University of Manitoba, Canada In 1957 when both authors were on staff of the Cereal Breeding Laboratory, Winnipeg, a program was conducted to attempt to determine the genome constitution of Aegilops crassa (6x). A total of 10 interspecific and 3 intergeneric F1 hybrids were produced with the aid of an embryo culture technique. Most of these were new combinations and it is primarily for this reason that the present results are being reported. The F1 hybrids were examined cytologically to determine chromosome pairing. The pairing frequencies are presented in Table 1. In 1958, KIHARA et al. concluded that the three genomes of Ae. crassa are DDMCR. Thus is any hybrid with this species, approximately 7 bivalents should be formed by pairing of the chromosomes of the two D genomes. In 12 of the above 13 crosses, sufficient pairing was observed to conclude that Ae. crassa is partly autoploid. However in the crosses with Ae. squarrosa and T. aestivum, where a third D genome is present in the hybrid, a high numder of trivalents would be expected. This was not observed in the present study indicating that the genome constitution may be somewhat more complex than previously suggested. The pairing in the hybrid with T. durum was remarkably low, only 1.05 bivalents per cell. Perhaps in T. durum there is a much more effective diploidizing gene than in the other species used in the study, which prevented the expression of the true degree of homology. |