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Abstract

Myriophyllum L. (watermilfoil) is the largest genus of the family Haloragaceae and belong the most species-rich genera of aquatic plants. Distinguishing of genus Myriophyllum is rather challenging. Despite the apparent taxonomic complexity, almost nothing is known about the cytogenetic structure of the genus in North America. In our study, we used flow cytometry and chromosome counting to recognize genome size and DNA ploidy level in species of genus Myriophyllum. We analyzed 294 European and 329 North American population samples. All species of genus Myriophyllum were found in both areas, except North American M. alterniflorum. Large cytotype variability (2x, 3x, 4x, 6x, 8x and 9x) was found in the USA and Europe. Cytotype variability was found in populations of M. heterophyllum where diploids and triploids were examined. Sympatric growth of diploid and triploid cytotypes was encountered in one population of M. pinnatum. Two populations of M. aquaticum in Europe (Hungary) had cytotype variability (6x and 8x) whereas all N. American populations were octoploids. Cytotype variability was also found in populations of M. sibiricum where hexaploids and nonaploids were observed. There was clear geografic isolation showing M. sibiricum as a hexaploids only in N. American and nonaploids in European populations. Only one nonaploid specimen of M. sibiricum was found in N. American populations and just one hexaploid of M. sibiricum in the European population. Nonaploids in USA and hexaploids in Europe of M. sibiricum were detected for the first time. Genome size (2C) ranged from 0.41 pg in diploid M. humile (2n=14) to 2.66 pg in nonaploid M. sibiricum (2n=63). These findings give evidence that a detailed study of cytotype composition. Last but not least, studies of ploidy variation have repeatedly proved necessary to elucidate the mechanisms of triggering the invasive behavior in plants.

Biography

T Kávová is a Molecular Geneticist with specialization on population-genetic studies. She is most interested in ecological topic with the implantation of new techniques in molecular analyses. Techniques that she perfectly controls range from basic lab work, through complete knowledge of molecular genetic techniques including sequencing to current flow cytometry specialization. The topic of her thesis is genetic and cytogenetic variability of Myriophyllum L. in the native and invasive area of the genus..