Comparative chromosomal localization of 45S and 5S rDNAs in 76 purple-fleshed sweet potato cultivars

Abstract

Background: In recent years, purple-fleshed sweet potato has been paid more and more attention because of its high nutritional value. However, the current studies on purple-fleshed sweet potato were still focused on the research and production of the related products. The research on its cytogenetics is relatively lagging behind, which cannot satisfy the study of genetic diversity of purple-fleshed sweet potato. Therefore, we carried out cytogenetic analysis on 76 purple-fleshed sweet potato cultivars, aim to analyze the chromosome structure and distribution of 45S rDNA and 5S rDNA in 76 purple-fleshed sweet potato cultivars.Results: We have found that only 62 purple-fleshed sweet potato cultivars with 90 chromosomes, and the others were aneuploid with 88, 89, 91, 92 chromosomes. The number of 45S rDNA in 76 purple-fleshed sweet potato cultivars varies from 16 to 21, with different signal sizes and intendities, and localized at the terminal or satellite of chromosomes. The number of 5S rDNA were relatively stable, 74 of the varieties investigated contained 6 sites, located at the terminal of chromosomes and near centromere. Only the Quanzishu 96 has 7 5S rDNA sites, and Yuzixiang 10 has 5 5S rDNA sites. In addition, rDNA analysis was also performed on two parents of Quanzishu 96. Both the two parents had 18 45S rDNA sites and 6 5S rDNA sites, which were different from the results of Quanzishu 96.Conclusions: For hexaploid sweet potato cultivars, there is genetic instability between purple-fleshed sweet potato cultivars. The 45S rDNA sites showed numerical variation, whereas conserved number of 5S rDNA sites were observed.