Genetic analysis and population structure of wild and cultivated wishbone flower (Torenia fournieri Lind.) lines related to specific floral color

Shikai Guan; Qian Song; Jinye Zhou; Haixia Yan; Yuxiang Li; Zibin Zhang; Dayan Tao; Shuming Luo; Youqiang Pan

doi:10.7717/peerj.11702

Genetic analysis and population structure of wild and cultivated wishbone flower (Torenia fournieri Lind.) lines related to specific floral color

PeerJ. 2021 Jul 5:9:e11702. doi: 10.7717/peerj.11702. eCollection 2021.

Authors

Shikai Guan^#¹, Qian Song^#¹, Jinye Zhou¹, Haixia Yan¹, Yuxiang Li², Zibin Zhang¹, Dayan Tao¹, Shuming Luo^{1

3}, Youqiang Pan⁴

Affiliations

¹ Flower Research Institute, Guangxi Academy of Agricultural Sciences, Nanning, Guangxi, China.
² Guangxi Academy of Agricultural Sciences, Nanning, Guangxi, China.
³ Plant Breeding Institute, Faculty of Agriculture and Environment, University of Sydney, Cobbitty, NSW, Australia.
⁴ Guangxi Crop Genetic Improvement and Biotechnology Laboratory, Guangxi Academy of Agricultural Sciences, Nanning, Guangxi, China.

^# Contributed equally.

Abstract

Background: The wishbone flower or Torenia fournieri Lind., an annual from tropical Indochina and southern China, is a popular ornamental plant, and many interspecific (T. fournieri × T. concolor) hybrid lines have been bred for the international market. The cultivated lines show a pattern of genetic similarity that correlates with floral color which informs on future breeding strategies. This study aimed to perform genetic analysis and population structure of cultivated hybrid lines comparing with closely related T. concolor wild populations.

Methods: We applied the retrotransposon based iPBS marker system for genotyping of a total of 136 accessions from 17 lines/populations of Torenia. These included 15 cultivated lines of three series: Duchess (A, B, C); Kauai (D, E, F, G, H, I, J); Little Kiss (K, L, M, N, P) and two wild T. concolor populations (Q and R). PCR products from each individual were applied to estimate the genetic diversity and differentiation between lines/populations.

Results: Genotyping results showed a pattern of genetic variation differentiating the 17 lines/populations characterized by their specific floral colors. The final PCoA analysis, phylogenetic tree construction, and Bayesian population structural bar plot all showed a clear subdivision of lines/populations analysed. The 15 cultivated hybrid lines and the wild population Q that collected from a small area showed the lowest genetic variability while the other wild population R which sampled from a larger area had the highest genetic variability.

Discussion: The extremely low genetic variability of 15 cultivated lines indicated that individual line has similar reduction in diversity/heterozygosity from a bottleneck event, and each retained a similar (but different from each other) content of the wild genetic diversity. The genetic variance for the two wild T. concolor populations could be due to our varied sampling methods. The two wild populations (Q, R) and the cultivated hybrid lines (I, K, M, N, P) are genetically more closely related, but strong positive correlations presented in cultivated lines A, C, E, M, and N. These results could be used to guide future Torenia breeding.

Conclusions: The genetic variation and population structure found in our study showed that cultivated hybrid lines had similar reduction in diversity/heterozygosity from a bottleneck event and each line retained a similar (but different from each other) content of the wild genetic diversity, especially when strong phenotypic selection of floral color overlaps. Generally, environmental factors could induce transposon activation and generate genetic variability which enabled the acceleration of the evolutionary process of wild Torenia species. Our study revealed that wild Torenia populations sampled from broad geographic region represent stronger species strength with outstanding genetic diversity, but selective breeding targeting a specific floral color decreased such genetic variability.

Keywords: Genetic diversity; Genetic structure; Plant breeding; Transposon; Wishbone flowers; iPBS.

Grants and funding

This work was supported by the Foundation for Development of Science and Technology, Guangxi Academy of Agricultural Sciences (inaugural funding); the Guangxi Natural Science Foundation (No. 2020GXNSFAA259064; No. 2020GXNSFAA297068; No. 2020GXNSFBA297074) and the Foundation for research team project supported by Guangxi Academy of Agricultural Sciences (GUINONGKE 2021YT135). There was no additional external funding received for this study. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.