Nine species (wild and cultivated) and some interspecific (wild × cultivated) hybrids were analysed by flow cytometry. This study confirms various polyploidy levels within cultivated species. DNA index varied by a factor of 1 to 3 for Dioscorea alata, 1 to 2.25 for Dioscorea bulbifera, and 1 to 2 for Dioscorea cayenensis-rotundata, depending on the clone or cultivar considered. In wild species, only one DNA index per species was obtained. Whenever a relationship between DNA index and chromosome number could be established, the size of genome 1C was evaluated in picograms and base pairs. Two genome sizes were observed: genome A in D. cayenensis-rotundata, Dioscorea abyssinica, Dioscorea mangenotiana, and Dioscorea praehensilis and genome B in Dioscorea togoensis. These genomes were small sizes, only 1.5 to 2.1 times larger than that of Arabidopsis. Key words: yams, Dioscorea, flow cytometry, DNA index, genome size.
Chromosome number in 10 varieties of Dioscorea cayenensis-rotundata ( Dioscoreaceae ) compound organism.