Karyotype and RAPD Analysis of Allium tuberosum Rottl. ex Spreng. and Three Specimens of Allium cepa L.

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Four specimens of the genus Allium, viz. A. tuberosum, A. cepa (Local), A. cepa (Indian large bulb) and A. cepa (Indian small bulb), were cytogenetically studied. In addition, DNA fingerprinting by using RAPD was also carried out to make a phylogenetic dendrogram. Allium tuberosum was found to possess 2n=32 chromosomes. On the other hand, 2n=16 chromosomes were observed in the other three specimens. The four specimens showed distinct centromeric formulae, which were 16m+12sm+4ac in Allium tuberosum, 10m+4sm+2ac in A. cepa (Local), 8m+8sm in A. cepa (Indian large bulb) and 9m+7sm in A. cepa (Indian small bulb). This result indicated that Allium tuberosum and A. cepa (Local) possessed more heterogeneous karyotypes. Satellites were found in Allium tuberosum, A. cepa (Indian large bulb) and A. cepa (Local) in different stains. In A. cepa (Indian small bulb), heteromorphicity in respect of centromeric position indicated the occurrence of a deletion at the short arm of the respective chromosome. The four specimens of Allium have distinct CMA- and DAPI-banding patterns. The number, location, intensity and percentage of GC- and AT-rich repeats were different in these specimens. With the help of CMA- and DAPI-banding it was possible to mark certain chromosomes specific for each specimen. Each specimen showed characteristic RAPD fingerprinting. The unique RAPD fragments could be used as markers for the respective specimens. The karyotype and RAPD data did not support the large bulb specimen as an autopolyploid of the small bulb specimen, but rather found maximum similarity between the two specimens. Moreover, the karyotype data of A. tuberosum obtained in this study was different from earlier reports, and thus needs a peer revision of its taxonomic status.