Cytogeographical Studies on Scilla indica in India-Triploids

Abstract

Scilla indica is widely distributed in central and southern parts of India and Sri Lanka, and is highly polymorphic, different populations in different geographical areas of the country looking like different species. Cytological studies on two phenotypically different populations of S. indica occurring in the Madras coastal areas have clearly revealed that both have the same chromosome number of 2n=45 and evidently represent naturally occurring triploids fitting very well under the established basic chromosome number of 15 for the species in the country. These were mistaken to be diploids (aneuploid races) with 2n=44, 45, 46 by the earlier workers apparently due to the reason that the diploid number of 2n=30 was not known at that time. The present study has also revealed the existence of two kinds of triploids in the area, the broad leaved variety consisting of autotriploids and the narrow-leaved variety consisting of allotriploids. While the autotriploids have chromosomes similar to those found in their diploid counterparts, the allotriploids are unique in their diploid set having two long chromosomes with subterminal primary constrictions, a type not encountered in any of the Indian Scillas but very common in European Scillas. Both populations are sexually sterile. Nevertheless, they are found well established with effective means of vegetative propagation through prolific production of bulbils at the leaf tips and underground daughter bulbs. Cytogeographically these populations are very interesting in that they are found restricted and isolated in the coastal areas of Madras in India with no other kind of Scilla other than these triploids occurring in the area. It is also significant to record that in no other area in the country except Madras, did the authors come across any naturally occurring triploids of this species.