Cytological studies in Saintpaulia Wendl.
American Journal of Botany 45(3): 177-182
ISSN/ISBN: 0002-9122 Accession: 024432964
Using standard cytological techniques, comparative analyses of a diploid and a tetraploid variety of Saintpaulia ionantha Wendl. were made. The reported 2n chromosome number of 30 for the diploid was confirmed, and the 2n number of 60 was newly established for the tetraploid studied. In contrast to the tetraploid, meiosis and subsequent microspore development were essentially normal in the diploid. Both varieties are heterozygous for chromosome inversions. Multivalent pairing occurred in the tetraploid which also is heterozygous for two different translocations and apparently has a deletion or duplication. Cytological chromosome maps of the diploid were prepared. These show an over-all chromomere size-gradient as well as repeated patterns of variation in chromomere size. A single nucleolus-organizer chromosome with a small satellite was found, and the organizer region was apparent. Pollen abortion is negligible in the diploid but is considerable in the tetraploid. On a volumetric basis, pollen of the tetraploid is 1.6 to 1.7 times larger than that of the diploid. The tetraploid is apparently an autopolyploid in which structural changes in the chromosomes have accumulated.