Milo, J., Department of Medicinal, Spice and Aromatic Crops, Agricultural Research Organization, The Volcani Center, Bet Dagan, 50250, Israel
Levy, A., Department of Medicinal, Spice and Aromatic Crops, Agricultural Research Organization, The Volcani Center, Bet Dagan, 50250, Israel
Ladizinsky, G., Faculty of Agriculture, Hebrew University of Jerusalem, Rehovot, Israel
Palevitch, D., Department of Medicinal, Spice and Aromatic Crops, Agricultural Research Organization, The Volcani Center, Bet Dagan, 50250, Israel

Chromosome behaviour at meiosis, isozyme studies and analysis of the chloroplast DNA restriction fragments were used to assess the phylogenetic relations among the three Papaver species of the section Oxytona. The multivalents observed in diplotene - diakinesis stages of meiosis of the hexaploid P. pseudo-orientale and its tetraploid hybrid with P. bracteatum indicate the autopolyploid nature of this section. Further evidence supporting this conclusion was obtained from isozyme analysis. The same number of isozymes was expressed in all the species regardless of their ploidy level. Inheritance studies conducted with Pgi, Dia and Acp allozymes demonstrated, for the first time, the transfer and expression of genetic material among these species. The differences found in the chloroplast DNA restriction fragments of the Oxytona species and of P. somniferum indicate intensive evolution of the chloroplast DNA in the genus Papaver. The similarity of the chloroplast DNA restriction patterns and of the isozymes in P. orientale and P. pseudo-orientale suggested that P. orientale was the female parent in the cross generating P. pseudo-orientale and that the latter species is of recent origin. © 1988 Springer-Verlag.