Abstract
Reed canarygrass (Phalaris arundinacea L.) has been recognized as a major invasive plant in the US in recent years. In Japan, the differences between the native and invasive genotypes are unclear. To identify these differences, chromosomal analysis using fluorescence in situ hybridization (FISH) with 5S/45S rDNA probes was carried out on 7 populations of putative native Japanese P. arundinacea and 3 exotic P. arundinacea. The results showed that all populations were tetraploids (2n=4x=28). The 45S rDNA were mapped on 4 sites corresponding with the ploidy level in all populations. On the other hand, the numbers of 5S rDNA sites differed among the populations. Moreover, the 5S rDNA sites differed among individuals even within the same populations. Thus, the chromosomal characteristics could not ensure that the putative native Japanese P. arundinacea are the native.
