Studies on the Genus Dioscorea L.

Abstract

Morphological and cytological studies have been made on 13 species of Dioscorea and their different polyploid forms. New chroomosome numbers have been recorded in D. deltoidea, D. hamiltonii, D. belophylla, D. sansibarensis and D. oppositifolia var. linnaei . Chromosome numbers of the Indian species range from 2n=20 ( D. deltoidea ) to 2n=100 (e.g. D. bulbifera, D. esculenta ) indicating a basic number of x=10 for this genus. Different polyploid races have been observed in 8 species studied, but a study of the epidermal peelings of the leaves shows that there is not much variation in the epidermal patterns between species as also within the polyploid series of any species. The nature of the tubers, occurrence and size of the bulbils, and the morphology of the epidermal hairs are of much taxonomic interest in the delimitation of species and varieties within a given species.