Comparative karyotypic analysis of annual and perennial populations of Lolium

Karyotypic characteristics of eight populations from six Lolium species were comparatively analyzed to provide more insight on annual and perennial ecotypes of the genus, particularly, in Lolium rigidum grown in Iran. The number of base chromosomes was X=7 for all populations examined. The ploidy level, however, was 2n=2x=14, with the exception of L. xhybridum which was tetraploid (2n=4x=28). Chromosomes in all populations were mostly metacentric. Karyotypic traits of the perennial ecotype of L. rigidum, showed greater similarity to the annual ecotype of the same species. Cluster analysis of karyotypic traits separated the tetraploid population from diploid populations. The diploid populations were divided into two distinct groups in which Lrg2 (perennial) and Lrg1 (annual) populations of L. rigidum, were grouped together and perennial populations of foreign origin formed a separate group. Principal components analysis (PCA) showed that the traits including difference between maximum and minimum relative length, long arm´s length, short arm´s length and total length of the chromosomes in the first component contributed the most to the variance among the populations. The byplot of the two major components, PC1 and PC2, separated annual and perennial populations of L. temulentum and L. xhybridum, respectively, from other populations which were divided into two distinct groups. Perennial and annual populations of L. rigidum grouped together. This group was located with a considerable distance from the group consisting of populations from all three ecotypes: perennial (L. perenne), biennial (L. multiflorum) and annual (L. persicum and L. rigidum). Based on the results presented here no specific relationship was observed between karyotypic characteristics and annual or perennial type of plants in the genus Lolium.