Distribution of rDNA loci in the genus Glycine Willd.

The objective of this study was to examine the distribution of rDNA loci in the genus Glycine Willd. by fluorescent in situ hybridization (FISH) using the internal transcribed spacer (ITS) region of nuclear ribosomal DNA as a probe. The hybridized rDNA probe produced two distinct yellow signals on r eddish chromosomes representing two NORs in 16 diploid (2n=40) species. Ane udiploid (2n=38) and aneutetraploid (2n=78) Glycine tomentella Hayata also exhibited two rDNA sites. However, the probe hybridized with four chromosom es as evidenced by four signals in two diploid species (Glycine curvata Tin d. and Glycine cyrtoloba Tind.) and tetraploid (2n=80) G. tabacina (Labill. ) Benth. and G. tomentella. Synthesized amphiploids (2n=80) of Glycine cane scens F. J. Herm. (2n=40) and the 40-chromosome G. tomentella also showed f our signals. This study demonstrates that the distribution of the rDNA gene in the 16 Glycine species studied is highly conserved and that silence of the rDNA locus may be attributed to amphiplasty during diploidization and s peciation.