Cyto-Molecular Characterization of Three Tacca Species from Bangladesh

Abstract

Three species of Tacca J. R. & G. Forst., namely T. plantaginea, T. chantrieri and T. integrifolia, were investigated cytogenetically and at the molecular level to solve their taxonomic rank. The diploid chromosome number 2n=28 was found in T. plantaginea and T. integrifolia whereas 2n=22 was found in T. chantrieri. This is probably the first report on the diploid chromosome number of T. plantaginea and T. chantrieri around the world. The three species differed in respect of centromeric formulae such as 22m+6sm in T. plantaginea, 18m+4sm in T. chantrieri and 28m in T. integrifolia. In addition to regular 2n=22 chromosomes, four to eight small chromosomes were found in some cells of T. chantrieri suggesting the probable occurrence of B-chromosome. In T. integrifolia, a pair of satellites was found on the short arm, one in each member of pair VI, after orcein and CMA staining but not in DAPI, revealing the GC-rich nature. A wide range of CMA- and DAPI-positive bands was found in the metaphase chromosomes of the three species. DAPI-fluoresced chromosomes were frequent in these three species. Six primer combinations were applied for RAPD analysis in the three species of Tacca to find out their genomic relationship. The three species showed some unique bands useful as markers for each species. Conventional and fluorescent karyotype together with RAPD fingerprinting indicated that T. integrifolia is distantly related to T. plantaginea and T. chantrieri. Therefore, the compilation of the above cytological and molecular information will be very useful for authentic identification of the three Tacca species. This genetic information will help in the proper conservation of and to make patent for the three threatened Tacca species found in Bangladesh.