Structure and Behavior of Chromosomes in Different Varieties of Aster Amellus L. and their mode of Origin

TLDR: Regular bivalent formation has been noted in all of them, inspite of the occurrence of structurally altered chromosomes, and the role of structural alterations of chromosomes in the origin of the different garden forms has been suggested.

Abstract: SUMMARYDetailed cytological study has been performed on six different horticultural varieties of Aster amellus, L. All the individuals have been found to contain 2 n = 18 chromosomes.Karyotype analysis has been done in five varieties, while in one variety, « mauve », the number has been determined from the meiotic count only. On the basis of the minute karyological differences between the different varieties, the role of structural alterations of chromosomes in the origin of the different garden forms has been suggested.From the present and the previous records, the importance of aneuploidy in the evolution of the different species of Aster has also been emphasized.Meiosis has been studied in four varieties. Regular bivalent formation has been noted in all of them, inspite of the occurrence of structurally altered chromosomes. It has been explained by the fact that these varieties have attained homozygosity for changes during cultivation with the possible elimination of heterozygous forms.