Dapi-Fluorescence Intensity Discriminates Between The Taxa In The Genus Reynoutria

J Suda1,2, B Mandák2 and K Bímová2,3

1 Department of Botany, Charles University, Benátská 2, Prague, CZ-128 01, Czech Republic
2Institute of Botany, Academy of Sciences of the Czech Republic, Pruhonice 1, CZ-252 43, Czech Republic
3Institute of Applied Ecology, Czech Agricultural University Prague, CZ-281 63, Kostelec nad Cernými lesy, Czech Republic

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Representatives of the genus Reynoutria (knotweed) rank among the most dangerous alien plants introduced to Europe. Three taxa spread rapidly in various man-made and semi-natural habitats: R. japonica (with two varieties - tetraploid var. compacta and octoploid var. japonica), R. sachalinensis (mostly tetraploid), and a taxon of hybridogenous origin R. ×bohemica (predominantly hexaploid). A variation in ploidy levels (4x, 6x, 8x) in the latter two taxa has been revealed recently in the Czech Republic1. Subsequent investigations using DAPI-flow cytometry detected an inter-species differentiation in the nuclei fluorescence intensity between plants with the same number of chromosomes. The relative fluorescence of the monoploid chromosome sets in R. japonica, R. ×bohemica, and R. sachalinensis were 100, 93.9-95.7 and 88.7-91.3 respectively.

The values suggested that:

1. R. japonica var. japonica is an autopolyploid descendant of var. compacta;
2. hexaploid R. sachalinensis arose by a fusion of non-reduced and reduced gametes of the tetraploid individual, the origin of the octoploid cytotype remaining rather speculative;
3. all the ploidy levels in R. ×bohemica arose by a hybridization between the corresponding cytotypes of R. sachalinensis and R. japonica.
1. Mandák B, Pysek P, Lysák MA, Suda J, Krahulcová A, Bímová K (2003). Annals of Botany 92: 265-272.