Comparison of ribosomal DNA sites inLolium species by fluorescencein situ hybridization

The position of the 18S-5.8S-26S and 55 rRNA genes have been physically mapped on the chromosomes of seven Lolium taxa. 18S-5.8S-26S sites were seen on two pairs of chromosomes in the inbreeding tare. In the outbreeding taxa six sites were found in the L. multiflorum, seven in L. perenne and nine in L. rigidum var. rigidum. Two 5S sites were found in each of the taxa. In the inbreeders, the 5S sites were found adjacent to the 18S-5.8S-26S sites on chromosome 2. In L. multiflorum and L. perenne the 55 sites were on the short arm of chromosome 3. However, in L. rigidum var. rigidum the 55 rDNA site was found in either of the two positions.