CYTOLOGICAL STUDIES IN THE GENUS AGROPYRON

Abstract

Eighteen species of the genus Agropyron from Western Canada, Russia, Siberia, and Denmark formed a polyploid series with a basic number of seven chromosomes. Di-, tri-, tetra- and octaploid forms were found among Western Canadian species; di-, tetra-, penta-, hexa- and decaploid forms among the Russian and Siberian species; di-, tetra- and hexaploid forms among the Danish species.The forms collected in Western Canada showed an extremely wide range of morphological variability both within and between the various species. This is probably due to natural hybridization such as has been reported between certain native species in Russia and Denmark. The cytology of these European species and their supposed hybrids has been studied here and has shown that natural crossing has probably taken place between diploid and hexaploid species in some cases and between tetraploid and hexaploid species in others. Some evidence of a similar situation among Western Canadian species has been found. Chromosome doubling, triploidy and aneuploidy occurred in certain of the latter. The relation of these phenomena to hybridization is discussed.