A study of chromosome association and chiasma formation in the amphidiploid between Lolium multiflorum and Festuca drymeja

Abstract

The chromosomes of Festuca drymeja are larger than those of Lolium multiflorum and the two complements can be distinguished in the F1 hybrid and allotetraploid. Chromosome associations at metaphase 1 in the amphidiploid was typical of an allopolyploid because all the bivalents were symmetrical, which indicates complete preferential homologous chromosome pairing. Chromosome behaviour within the two genomes of the amphidiploid differed from that in the corresponding diploid species. The mean chiasmata per bivalent of the F. drymeja complement was much higher in the allotetraploid than in the diploid species and there was a corresponding reduction in the L. multiflorum complement compared with the diploid. Total chiasma frequency of the amphidiploid was determined by the additive effect of the two genomes but there is evidence that the distribution of chiasmata was related to the specific genomes.