Chromosome divergence in the genus Cuscuta and its systematic implications BATIA

Cuscuta L. plants are holoparasites with high chromosome divergence. Species representing the three subgenera of the genus were checked for their chromosome number, length and behaviour. Chromosome numbers range between 2n = 8 and 2n = 60, and their size, although roughly uniform within species, varies between 1–23μm. On the whole, size or number of Cuscuta chromosomes cannot be used as diagnostic criteria, except for very few species with unique numbers or sizes. Some associations between certain systematic entities and chromosome characters can be inferred. Species of the Old World of subgenus Cuscuta Engelm. are characterized by inverted meiosis and apparently by holocentric chromosomes, whereas species of the two other subgenera, subgenus Motiogyna Engelm. and subgenus Grammica Yuncker, undergo the regular process of meiosis and have monocentric chromosomes. The presence of holocentric chromosomes does not seem to be associated with their number.