School of Life Sciences, Jiangsu Normal University, Xuzhou, 221116, Jiangsu, China.
Shanghai Key Laboratory of Plant Functional Genomics and Resources, Shanghai Chenshan Botanical Garden, Shanghai, 201602, China.
Chromosome Res. 2024 Nov 28;32(4):14. doi: 10.1007/s10577-024-09758-8.
The origin of hexaploid sweetpotato [Ipomoea batatas (L.) Lam.] remains controversial. Comparative karyotype analysis is particularly useful in determining species relationships and the origin of polyploid species. In previous study, we developed a set of oligo probes and identified all chromosomes of Ipomoea nil, a model diploid Ipomoea species. Here, we found that this set of oligo probes could be used to identify all chromosomes of sweetpotato and its wild relatives with different ploidy. Karyotypes based on individually identified chromosomes were established and the number and position of 5S and 35S rDNA loci were determined for these Ipomoea species. Comparison of their karyotypes revealed distinct variations in the karyotypic parameters. Karyological relationships among these species were revealed by principal coordinate analysis (PCoA) based on six quantitative parameters (x, 2n, TCL, M, CV and CV). These results show that I. trifida is the most closely related diploid species to sweetpotato, and other diploid species could be excluded from consideration as its possible diploid ancestor. In addition, our study also provides cytogenetic evidence for the segmental allopolyploid hypothesis of sweetpotato origin.
六倍体甘薯[Ipomoea batatas (L.) Lam.]的起源仍然存在争议。比较染色体组型分析在确定物种关系和多倍体物种的起源方面特别有用。在之前的研究中，我们开发了一套寡核苷酸探针，并鉴定了模式二倍体甘薯种Ipomoea nil 的所有染色体。在这里，我们发现这套寡核苷酸探针可用于鉴定不同倍性的甘薯及其野生近缘种的所有染色体。基于个别鉴定出的染色体建立了核型，并确定了这些甘薯种的 5S 和 35S rDNA 基因座的数量和位置。对它们的染色体组型的比较揭示了在染色体组型参数方面的明显差异。基于六个定量参数（x、2n、TCL、M、CV 和 CV）的主坐标分析（PCoA）揭示了这些物种之间的亲缘关系。这些结果表明，Ipomoea trifida 是与甘薯关系最密切的二倍体种，其他二倍体种可以排除作为其可能的二倍体祖先的考虑。此外，我们的研究还为甘薯起源的片段异源多倍体假说提供了细胞遗传学证据。
