New Estimation of Genome Size in the Highly Diverse Genus Begonia.

Authors: SONG, JINJIN - The Ohio State University; GINORI, JULIAN - University Of Florida; URBANO, FREDDY - The Ohio State University; THOMPSON, LILY - The Ohio State University; HUO, HEQIANG - University Of Florida; Altland, James; WU, XINGBO - University Of Florida; MA, YU - The Ohio State University

Submitted to: Journal of the American Society for Horticultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/15/2026
Publication Date: 3/4/2026
Citation: Song, J., Ginori, J., Urbano, F., Thompson, L., Huo, H., Altland, J.E., Wu, X., Ma, Y. 2026. New Estimation of Genome Size in the Highly Diverse Genus Begonia.. Journal of the American Society for Horticultural Science. 151(3):161–170. https://doi.org/10.21273/JASHS05584-25.
DOI: https://doi.org/10.21273/JASHS05584-25

Interpretive Summary: Begonia, one of the largest and most diverse plant groups, has been widely cultivated for centuries and is valued for its ornamental beauty. However, understanding its genetic makeup has been difficult because species within this genus vary greatly in genome size, chromosome number, and ploidy level. This complexity has posed challenges for evolutionary studies, taxonomic classification, and plant breeding. Until now, limited genomic data have hindered progress in these areas. To address this problem, genome sizes of 93 Begonia accessions representing 27 sections were estimated using flow cytometry. The study revealed a fivefold variation in genome size, ranging from 0.24 picograms to 1.19 picograms of DNA per cell. The largest genomes were found in sections such as Tetraphila, while the smallest occurred in Wagenaria. Significant differences were also observed within certain sections, including Ephemera, Gireoudia, and Pritzelia, which showed up to fivefold variation among species. These findings confirm that genome size diversity is widespread and not linked to geographic origin. By providing accurate genome size estimates, this research has expanded the genetic foundation for Begonia. These data will help scientists design sequencing projects, interpret evolutionary patterns, and improve taxonomic classification. For breeders, knowledge of genome size can guide hybridization strategies by identifying potential compatibility issues caused by differences in chromosome number or ploidy level. Furthermore, understanding genome size variation offers clues about how these plants adapted to diverse environments, which can inform conservation and breeding efforts.

Technical Abstract: Begonia is one of the most diverse plant genera, native to tropical and subtropical regions worldwide. Throughout the long cultivation history, Begonia has become widely spread across the Americas, Asia, and Africa. Besides morphological, ecological, and geographic origin differences, Begonia species also significantly vary in genome size. In this study, flow cytometry was employed to estimate the genome sizes of 93 Begonia accessions representing 27 sections of the genus. The results showed a wide range of 1C DNA values, from 0.24 pg in B. convolvulacea to 1.19 pg in B. polygonoides. Sections Tetraphila, Knesebeckia, and Parvibegonia had the largest mean genome sizes, whereas Wagenaria showed the smallest mean genome size. Significant variation in genome size was observed among individual accessions within the sections Ephemera, Gireoudia, and Pritzelia. These data can expand the genomic foundation for Begonia and provide a valuable resource for future genomic and genetic research, advancing breeding effort in this genus.