Endoreduplication and Mixoploidy During the Cell Cycle in Cannabis sativa

Endoreduplication and mixoploidy are widespread but poorly characterized phenomena in Cannabis sativa, a species notable for its rapid growth and high morphological variability. In this study, we analyzed 12 accessions using flow cytometry, chromosome counts, and fluorochrome banding to investigate organ-specific patterns of endopolyploidy and the occurrence of mixoploidy. Roots and cotyledons consistently exhibited high levels of endoreduplication, with substantial proportions of 8C nuclei and above, whereas the first pair of leaves displayed a profile similar to that of adult foliage, dominated by 2C nuclei. Cycle value and endocycle index calculations confirmed significant differences among organs, with roots and cotyledons showing markedly higher endoreduplication levels than leaves. Chromosome counts revealed the expected diploid number (2n = 20), but we also detected triploid and tetraploid cells in several accessions, indicating somatic mixoploidy. The presence of endoreduplication and mixoploidy suggests that C. sativa exhibits complex cell cycle regulation during early development. Fluorochrome banding revealed GC- and AT-rich DNA regions. Sex chromosome candidates are heterochromatic and contain AT-rich DNA. These findings expand the cytogenetic knowledge of the species and provide a basis for future studies on the developmental and evolutionary significance of somatic genome variation in C. sativa.