A representative fluorescent in situ hybridization (FISH) detection of nuclear organizing regions (NORs) in an octoploid switchgrass cultivar. (A) A root tip spread prepared from ‘Blackwell’ (2n = 8X = 72) and stained with acetocarmine. (B) The same cell as in (A) with chromosomes stained with DAPI (pseudocolored in red) and subjected to FISH with a NOR probe (pseudocolored in green). There are three types of pTa71 FISH sites in octoploids (see also Supplemental Fig. 2; Table 5): (F) interstitial (located between the centromere and telomere), (G) at both telomeres on an isochromosome, and (H) telomeric. For comparison, (B), (C), and (D) show the acetocarmine-stained chromosomes from (F), (G), and (H), respectively.