Morphological diversity of chromosomes bearing ribosomal DNA loci in Brachiaria species

作者：Akiyama Yukio^*; Yamada Akiyama Hitomi; Ebina Masumi

来源：Grassland Science, 2010, 56(4): 217-223.

DOI：10.1111/j.1744-697X.2010.00197.x

• Brachiaria
• fluorescence in situ hybridization
• polyploidy
• rDNA

The genus Brachiaria comprises approximately 100 species distributed across tropical and subtropical regions of the world. The objective of the present study was to identify and characterize the homo(eo)logous chromosomes bearing rDNA in six Brachiaria accessions including three accessions of B. brizantha, Brachiaria hybrid cv. Mulato, B. humidicola and B. ruziziensis by application of fluorescence in situ hybridization (FISH) with 5S and 25S rDNA probes. Results showed that the numbers of 25S rDNA loci, but not 5S rDNA loci, correspond to ploidy levels in all Brachiaria species. The morphological shapes of rDNA chromosomes showed differences not only between species but also within a species. These results indicate co-existence of different genomes in the species, that is, allopolyploidy. However, there are too many types of rDNA chromosomes in B. brizantha to be explained as solely a consequence of allopolyploidy. Although B. brizantha is known to be an aposporous plant that can produce maternal clone without fertilization, chromosomal rearrangements due to cross-hybridization with other species were suggested.

• 出版日期2010-12