Cytogenetic Studies in Artificially Raised Interspecific Hybrids of Papaver IX

On the bivalents-association in the meiosis of the PMC of Papaver somniferum

Abstract

1. In a race of Papaver somniferum are found 11 bivalents in its diaphase of the PMC, which show the kinds of association as 6 rings, 2 side by side union or, rarely, 2 open rings, 1 end to end union, 1 small ring and 1 largest side by side Union or open ring. While in another race there were found only ring or open ring configurations instead of side by side or end to end unions.
2. There were observed in the former very loose associations “bivalents-associations, ” between 2 pairs of ring bivalents or one pair of side by side bivalents, and also between a ring and an end to end bivalent. In the latter race 4 associations of ring bivalents were found.
3. P. somniferum is an amphitriploid, which has probably been derived as follows: an interspecific hybrid is raised between 2 species, one having 4 chromosomes and the other 3 chromosomes as their haploid complements, then the chromosome sets were doubled causing an amphidiploid, namely 2(4+3)=2(7). This amphidiploid is crossed with a plant which is closely related to one parent having 4 haploid chromosomes, then the whole sets are doubled again, namely (3+4)2=2(7), and then 2(7+4)=2(11).
4. The association or pairing of the two bivalents, “the bivalents-association” was discussed.
The writer's hearty thanks are due to Prof. K. Fujii for his kind advice in the course of the investigation. The expence of carrying out the present work was partly defrayed out of a grant from the Japan Society for the Promotion of Scientific Research, to which I tender my thanks.