Cryptopolyploidy in Bunias (Brassicaceae) revisited - A flow-cytometric and densitometric study

The concern of the present analysis is the hypothetical 'cryptopolyploidy', a concept basically of historical interest only, but discussed again by Ba ttaglia (1996) in a recent treatment of the term and its historical backgro und. Melinossi (1935), while reanalyzing erratic observations on the crucif ers Bunias erucago and B. orientalis by Jaretzky (1928a), found 2n = 14 in both species but twice the chromosome volume in B. erucago compared with B. orientalis. Melinossi considered 'cryptopolyploidy' in B. erucago, i.e., s he discussed pairwise fused chromosomes on a tetraploid basis or endoredupl icated (and thus binemic) chromosomes in this species. Cryptopolyploidy has also been claimed by Pannocchia-Laj (1938) in Vinca difformis (Vincaceae). Battaglia (1996) criticized the term 'cryptopolyploidy' because, in his op inion, the genuinely polyploid status of these plants is not hidden ('crypt o') but phenotypically (from herbarium specimens) recognizable. He coins th e term 'phenopolyploidy', i.e., "phenotypic polyploidy disagreeing with the karyotype numerically evalated". We measured genome size of B. orientalis and B. erucago (both 2n = 14) by Feulgen densitometry and propidium iodide flow cytometry. Surprisingly, B. erucago (the annual species with 2.13 pg, 1 C) turned out to have only 0.81-fold the DNA amount of B. orientalis (the perennial species with 2.64 pg, 1 C). Therefore, any kind of genetically p olyploid status in B. erucago is out of the question. Only speculative sign ificance can be ascribed to the terms 'cryptopolyploidy' and 'phenopolyploi dy'.