Tetraploid Male Fertile Pelargonium crispum Hybrids and Their Use in Interspecific Hybridization

Pelargonium crispum hybrids (section Pelargonium) are attractive ornamental plants with a long breeding history. Due to the domestication effect a low level of genetic and phenotypic variation is shown in seedling populations after cross-breeding with available cultivars. The genus Pelargonium offers with over 250 wild species in 16 sections a large unutilized genetic diversity. However, crossing barriers like different ploidy levels limit their use for hybridization. Here are shown preliminary results for polyploidization of diploid P. crispum hybrids (2n=2x=22) and their use for interspecific hybridization. Seedlings of P. crispum hybrids (cotyledon stage) were treated with a 200 mu M solution of amiprophos methyl on three consecutive days. Morphologically altered plants were investigated by stomata length measurement and flow cytometry. Probably tetraploid or mixoploid (4x/2x) genotypes could be selected and somatically segregated by the formation of adventitious shoots in vitro. Regenerated plants were characterized morphologically, by flow cytometry and through genotyping. Tetraploid regenerants were used in reciprocal cross-breeding with cultivars of P. xdomesticum (2n=4x=44).