Cytogenetical Investigations in Relation to the Mechanism of Evolution in Hexaploid Solanum nigrum L.

Abstract

Solanum nigrum L. shows a polyploid series with n = 12, 24 and 36 (ref. 1). Although a considerable amount of work has been done on the three cytotypes, yet there is a lot of controversy about the nature of polyploidy and the course of evolution in hexaploid Solanum nigrum². An ideal method for tracing the mechanism of evolution of the forms with higher chromosome numbers in species showing polyploid series is by producing these artificially. It has been possible for us to synthesize the hexaploid Solanum nigrum by crossing the naturally occurring tetraploid with diploid and then raising the triploid, through colchicine treatment, to the hexaploid-level. This note is concerned with the nature of polyploidy and the probable mechanism of evolution in hexaploid Solanum nigrum as brought out by a comparative morphological and cytogenetical study of the synthetic and the naturally occurring type.