Cytogenetic studies in Papaver L.; the x= 6 and x= 7 diploids

Although hybridization between species in Papaver is difficult, a combination of karyotypic and genomic analysis has allowed the definition of up to six, apparently independent genomes, in the 2n= 12 and 1n= 14 diploids. In the 2n= 14 group there is considerable karyotypic differentiation and karyotypes off. atlanticum and P. hybridum are sufficiently dissimilar from each other and from the rest to allow the recognition of the two genomes as unique although no hybrids with other x= 7 diploids were produced. The genome of P. atlanticum is defined as C₇C₇ and that of P. hybridum H₇H_7.P. alpinum and P. rhaeticum only hybridized successfully with each other and the near perfect bivalent formation in their hybrid, together with the extreme similarity of their karyotypes, suggests that they are very closely related. They are designated J₇J₇. All the other x=7 diploids are karyotypically similar and the analysis of meiosis in their hybrids demonstrates thay they all share the same genome to some extent. There is however some differentiation among them. P. commutatum, P. glaucum, P. macrostemum and P. rhoeas are genomically very similar and all can be regarded as A₇A₇. P.fugax and P. tauricola appear to share an identical genome, partially differentiated from A₇A₇ and are defined as A²₇A²₇ while P. postii, although showing some little homology with A₇A₇ is sufficiently differentiated from it to be regarded as more distant than A²₇A²₇ and is described as A³₇A³₇. Although no hybrids between the two 2n= 12 diploids P. apulum and P.pavoninum were produced their karyotypes are sufficiently different to be individually recognized. The only hybrid produced between the x= 6 and x= 7 groups (P. apulum×P. hybridum) showed no homology between the chromosomes of the two genomes and, although this may not be true for any other x=6/x=7 combinations it is best to recognize the two x= 6 genomes as independent of the x= 7. The genome of P. apulum is thus regarded as I₆I₆ and that of P. pavoninum as P₆P₆.