Cytological studies in Indian Viscaceae. I. Chromosome study and karyotype analysis inViscum capitellatumSm.

Abstract

Detailed karyomorphological analysis of a species (Viscum capitellatum Sm.) in the family Viscaceae is reported for the first time. The exceptionally large chromosomes in V. capitellatum probably represent the largest chromosomes in dicot angiosperms. The chromosome number of the species has been found to ben= 10 and 2n = 20. One pair of the chromosomes is heterochromatic. It is suggested that unequal crossing over of a segment between the homologous chromosomes has resulted in one duplicate chromosome and the other deficient.

Analysis of Meiotic Chromosome Behaviour in Diploid Individuals of Chrysanthemum zawadskii and Related Species (Asteraceae): Evidence for Chromosome Rearrangements

“…Also, the bivalents included at least one or two distinct bivalents, with the two chromosomes differing in length and/or centromere position. As the presence of such bivalents does not hinder chromosome segregation in later meiotic stages, they were likely formed by an unequal crossing-over between homologous chromosomes, as reported in other angiosperm taxa, including Viscum (Soman and Bhavanandan 1993). Thus, chromosome rearrangements, such as reciprocal translocations and unequal crossing-over, appear to be prevalent in the three Chrysanthemum species, resulting in gametes with different chromosome complements.…”