QTL dissection of floral traits in Streptocarpus (Gesneriaceae)

Abstract

Flower shape and colour are key plant traits which are often strongly correlated with pollinator choice and reproductive isolation. To understand the genetic changes underlying variation in these traits, we performed the first QTL analyses of these traits in Streptocarpus (Gesneriaceae) using a segregating backcross (BC) population of (S. rexii × S. grandis) × S. grandis. Composite traits of floral dimensions were dissected into smallest definable subtraits to examine the efficiency of QTL mapping and correlation between composite and subtrait-specific QTLs. Strong dominance effects were observed in the F1 for many S. rexii traits but for few S. grandis traits. In the BC plants new phenotypes appeared that may be the result of transgressive segregation. Many phenotypic correlations were found between floral dimension traits, which was probably due to the co-localisation of QTLs on the linkage groups. Two regions were associated with large numbers of size and shape traits (17 linked on LG1 and eight linked on LG12), to which the first principal component was also mapped. QTLs of composite traits were mostly overlapping with subtraits, although a few QTLs were newly discovered in subtrait mapping. Strong QTLs were detected for time to flowering and for floral pigmentation traits, ventral lobe pigmentation and the yellow spot. The absence of linkage of floral dimension traits and flower pigmentation suggests that genetic regulation of floral form in Streptocarpus allows versatility, perhaps allowing fast response to changing selective pressures from pollinators.

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Availability of data and materials

QTL data used in this study are included in the manuscript and supplementary materials.

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Acknowledgements

The authors would like to thank Sadie Barber, Nathan Kelso, and Andrew Ensoll for growing the plant material at the Royal Botanic Garden Edinburgh (RBGE). We also thank Michelle Hart, Laura Forrest, and Ruth Holland for supporting the molecular laboratory work, and Duncan Reddish for ICT support of the analysis servers at RBGE. Prof. Pete Hollingsworth (RBGE) for general support and facilitating the research associateship for KN at RBGE, and Prof. Andrew Hudson (University of Edinburgh) and Hao-Chun Hhu (National Taiwan University) for discussions on analytical methods. KN received supports from the Edinburgh Botanic Garden (Sibbald) Trust [2018#18], the Japan Society for the Promotion of Science [JSPS KAKENHI Grant Number 15K18593; 18K06375], and the Sumitomo Foundation [170204]. Computations were partially performed on the NIG supercomputer at ROIS National Institute of Genetics in Japan. RBGE and Biomathematics and Statistics Scotland are supported by the Rural and Environment Science and Analytical Services Division (RESAS) of the Scottish Government.

Funding

PhD scholarship at the University of Edinburgh for Yun-Yu Chen. Edinburgh Botanic Garden (Sibbald) Trust [2018#18], the Japan Society for the Promotion of Science [JSPS KAKENHI Grant Number 15K18593; 18K06375], and the Sumitomo Foundation [170204] for Kanae Nishii.

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Y-YC: Methodology, Formal analyses, Investigation, Writing – Original Draft; KN: Conceptualization, Formal analyses, Investigation, Writing – Original Draft, Resources; CK: Writing – Review & Editing, Supervision; CH: Formal analyses, Writing – Review & Editing, Supervision; MM: Conceptualization, Formal analyses, Investigation, Resources, Writing – Original Draft, Review & Editing, Supervision, Project administration.

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Correspondence to Kanae Nishii.

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R/qtl v1.39-5 package code used here was obtained from https://rqtl.org/download/.

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Chen, YY., Nishii, K., Kidner, C. et al. QTL dissection of floral traits in Streptocarpus (Gesneriaceae). Euphytica 216, 110 (2020). https://doi.org/10.1007/s10681-020-02647-1

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Keywords

  • Flower dimension
  • Floral traits
  • QTL mapping
  • Standard interval mapping
  • Streptocarpus
  • Gesneriaceae