Metaphase I bound arms and crossing over frequency in rye III. Non-chiasmate bonds in desynaptic plants

Summary

In order to analyze the correspondence between the number of metaphase I bonds and the chiasma frequency of specific chromosome arms in desynaptic plants, two F1 hybrids were backcrossed to the parental inbred lines. The plants obtained were desynaptic. Some of these plants were heterozygous for a prominent telomeric C-band in chromosomes 1R (long arm) and/or 2R (short arm). From the frequency of bound arms at metaphase I and the frequency of recombined chromosomes at anaphase I in the arms considered, estimates of chiasma frequencies have been derived. The results have been compared with those obtained for the F1s between inbred lines from which the desynaptic plants were produced (Giraldez and Orellana, 1979; Orellana and Giraldez, 1981) as well as with those obtained in an open pollinated variety of rye (Orellana and Giraldez, 1981). The excess of anaphase I parental chromosomes found in the desynaptic plants can be explained on the assumption that some of the bonds appearing at metaphase I are achiasmate and a remnant of prophase pairing.