Genome Size And Number Of Ribosomal Dna Loci In The Genera Musa And Ensete

J Bartoš, O Alkhimova, M Dolezelová and J Dolezel

Laboratory of Molecular Cytogenetics and Cytometry, Institute of Experimental Botany, Sokolovská 6, 77200 Olomouc, Czech Republic
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    Nuclear DNA content and genomic distributions of 5S and 45S rDNA sequences were examined in nineteen diploid accessions of the genus Musa representing its four sections, and in Ensete gilletii. In Musa, 2C DNA content ranged from 1.130 to 1.561 pg, M. balbisiana (section Eumusa with x = 11) having the lowest DNA content. M. beccarii, the only representative of section Callimusa (x = 10) analysed in this study, had the highest 2C nuclear DNA content (1.561 pg). Species belonging to sections Rhodochlamys (x = 11) and Australimusa (x = 10) had 2C DNA contents ranging from 1.191 to 1.299 pg and from 1.435 to 1.547 pg, respectively. E. gilletii (x = 9), which represents a related genus, had a small 2C DNA content (1.210 pg), but the highest number of 45S rDNA loci (four chromosome pairs). M. beccarii was the only species bearing six 45S rDNA sites (three chromosome pairs). Most of the rDNA loci were localized in distal chromosome regions. There were also differences in signal intensity, indicating variation in copy number between rDNA sites. 5S rDNA loci could be seen in all accessions studied, and their chromosomal position was characteristic for the given section. Five 5S rDNA sites were observed in a cultivar ‘Pisang Mas’ and in M. beccarii. The relationship between genome size and the number of nucleolus-organising regions is discussed, as well as the allopolyploid origin of some of the Musa species.