Effect of the Small Iso B and Deficient B Chromosomes on the Pairing of Standard B Chromosomes in Rye

Abstract

The pairing of standard B chromosomes in rye plants with a small iso B or deficient B chromosome in addition to several standard B chromosomes, viz., the 2 stB+1 siB plant, the 2 stB+1 defB plant and the 4 stB+1 defB plant, was observed in comparison with the 2 to 5 stB plants and with the 2 stB+1 liB plant. Frequencies of the pairing of standard B chromosomes in the former three plants were considerably lower than those in the latter plants. This indicates that the presence of the small iso B or the deficient B chromosome reduces the amount of pairing between standard B chromosomes. This may be due to the deficience of a special distal segment of the long arm of the standard B chromosome.