Abstract
The parentage of the Potamogeton hybrids P. ×nomotoensis Kadono & T. Noguchi and P. ×yamaga- taensis Kadono & Wiegleb (Potamogetonaceae) was studied by analyzing the plastid-encoded rbcL gene and nuclear-encoded internal transcribed spacer (ITS) from the hybrids and putative parents. The results showed P. ×nomotoensis to be a hybrid between P. natans and P. maackianus and P. ×yamagataensis a hybrid between P. natans and P. oxyphyllus. The latter is the first documentation of a hybrid between diploid and tetraploid species in Japan.
