Colchicine induced quadrivalent formation in Helianthus: evidence of ancient polyploidy.

The premeiotic treatment of microsporocytes of Helianthus annuus and H. laciniatus (x= 17) results in the formation of multivalent chromosome configurations at meiosis in these 'diploid' species. This is interpreted to mean that colchicine has disrupted the normal attachment of genomes to the nuclear membrane and allowed synapsis of the ancestral genomes, indicating the polyploid origin of these 'diploid' species. This technique should be of importance in generating intergenomal recombination in classical allopolyploid agronomic species because it could produce new genotypic combinations normally impossible to obtain.