No abstract

-Karyotype and meiotic studies were performed in 16 populations of seven Arenaria species growing in Iran. All the species studied showed 2n = 2x = 22 chromosome number supporting the earlier report on A. persica, A. insignis and A. gypsophiloides while the chromosome numbers of A. polycnemifolia, A. zargariana, A. szowitsii and A. minutissima are new to science. The chromosomes were mainly metacentric and submetacentric. The species studied differed signifi cantly in total size of the chromosomes, size of the short arms and the long arms, indicating the role of quantitative genomic changes in the Arenaria species diversifi cation. They also differed in their karyotype formulae indicating the occurrence of structural changes in their chromosomes. Meiotic analysis showed quadrivalent formation in Moorchegan population of A. persica and Kandovan population of A. insignis possibly due to the occurrence of heterozygote translocation between two pairs of chromosomes which in turn may increase the amount of genetic variability in the next generation. Cytomixis led to the formation of unreduced pollen grains in Mishoodagh population of A. gypsophiloides var. glabra, while B-chromosomes were observed in A. insignis and A. polycnemifolia species.

Summary Karyotypic analyses were performed in twenty populations of fourteen Bromus species and varieties from three sections of Bromus L., Genea Dum., and Pnigma Dumort., growing in Iran for the first time. The chromosome numbers of B. stenostachyus, B. tomentosus and B. kopetdaghensis are new and new polyploidy level has been reported for B. cappadocicus, B. erectus, B. variegatus and B. tomentosus. The ANOVA and LSD tests revealed a significant differences (pϽ0.01) in the size of chromosomes as well as chromosome arms among the populations of each species, among species with similar somatic chromosome numbers in each section and also among the three sections studied, indicting the role of the chromatin change in the species diversification in the genus Bromus. PCA analysis showed that the mean chromatin length of the chromosomes is one of the most variable karyotypic features among the Bromus species studied. Pearson correlation determined among the karyotypic features showed that the increase in the mean chromatin length has been accompanied with an increase in the size of both short and long arms of the chromosomes. The increase in the mean chromatin length showed a significant correlation with the TF percentage therefore increasing the level of karyotype symmetry.