Chromosomal polymorphism in isolated populations of Elymus (Agropyron) in the Aegean:

Abstract

Elymus diae is an octoploid (2n = 56) littoral species that grows in small isolated populations on the Aegean islands. A striking chromosomal polymorphism was found in twenty plants raised from seeds collected from four natural populations. All four populations had unique satellite and marker chromosome constitutions. Further chromosomal polymorphism was observed among plants originating from one of these populations. There were similarities in the appearance of the satellite chromosomes in E. diae, E. rechingeri and E. striatulus which denotes a close relationship between the three species. This is ascertained by a karyotype analysis of a polyhaploid individual of E. diae. The genome formula J4J4J(4)J(4)J5J5J6J66 or J4J4J(4)J(4)J(1)J(1)J6J66 was suggested for the species. Analysis of the satellite and marker chromosomes in 33 plants raised from seeds obtained in the greenhouse, following open pollination, inferred a predominance of self-fertilization or intrapopulation crosses. Aneuploids were found among plants raised from seeds collected in nature or obtained in the greenhouse. During meiosis, paired chromosomes usually appeared as bivalents and rarely as multivalents. Univalents occurred frequently which might be related to the prevailing chromosomal polymorphism. In the polyhaploid, most of the pollen mother cells had 4–7 bivalents which evidenced the presence of two closely related genomes. During the first pollen mitosis, chromosome numbers of 28 and 27 were observed in octoploid plants, whereas in the polyhaploid there were variable chromosome numbers.