Abstract: By means of fluorescence in situ hybridization (FISH), we located and analyzed the sites of the 45S rDNA on the F₁ hybrids of S. bicolor × S. propinquum and S. dochna×S.propinquum. Two signals of 45S rDNA were mapped on the mitotic metaphase chromosomes in the F₁ hybrids, respectively, and one signal was present on a bivalent during meiotic of synaptene, diakinesis, and metaphase I. We inferred that the two mitotic chromosomes carrying 45S rDNA were homolo-gous pairs. Considering the signals of 45S rDNA location during meiotic process, chromosome pairing of these two F1 hy-brids was normal with an average pairing configuration of 2n=2x=20 (10 II). Our results indicated that 45S rDNA could provide a landmark for identification of individual chromosome during meiosis indirectly.