Mapping of 18-26S rDNA loci in four species of the genus Paris by fluorescence in situ hybridization(FISH)
18-26S rDNA在4种重楼属植物中的定位

S rDNA loci were mapped on chromosomes in four species of Paris , and the number and position of rDNA sites in these species were compared for analysis of the distribution of the sites. All the plants were diploids, and the genome consisted of five chromosomes, A, B, C, D and E. (1) P. polyphylla var. yunnanensis, 2n=10=6m 4t. Two 18_26S rDNA loci were detected on the short arms of C and D chromosomes; (2) P. forrestii , 2n=10=6m 4t. One locus was detected on the long arm of B chromosome, and also two loci on the short arms of C and D chromosomes; (3) P. axialis . 2n=10=6m(2sat) 4t(2sat) 1-2B. Two loci were detected on the short arms of C and D chromosomes. One locus was detected in the cell with two B_chromosomes (B), but none was detected in that with only one B chromosome, indicating that rRNA gene existed on B chromsome, and an unequal division occurred during mitotic cycle of B_chromosomes. (4) P. daliensis , 2n=10=4m 2sm 2st 2t. One locus was detected on the short arm of D chromosome. The signals of 18_26S rDNA appeared not only in the second constriction but also in the other regions of chromosome. It is noteworthy that one locus was detected in the terminal region on the short arm of C chromosome in all the four species studied.