Mitotic index studies on edible cocoyams (Xanthosoma and Colocasia spp.)

Mitotic index studies were carried out on three cultivars of Xanthosoma and four cultivars of Colocasia. Young healthy roots (about 15 mm) were collected at 2 hourly intervals from 6:00 am to 8:00 pm. Root tips were fixed in 1:3 ethanol: acetic acid for 24 h and stored in 70% ethanol prior to squashing in FLP orcein. Microscopic counts showed that the dynamics of mitosis varied slightly between the two groups of cultivars. The peak of metaphase remained between 12:00 noon and 2:00 pm for most of cultivars but one (NCY 00Sa), which had its metaphase rising to a peak between 2:00 and 4:00 pm. This suggests that the best time to harvest root samples for optimum metaphase is immediately before 12:00 noon.