Identification of quantitative trait loci governing subgynoecy in cucumber
QTL-seq analysis identified three major QTLs conferring subgynoecy in cucumbers. Furthermore, sequence and expression analyses predicted candidate genes controlling subgynoecy.
The cucumber (Cucumis sativus L.) is a typical monoecious having individual male and female flowers, and sex differentiation is an important developmental process that directly affects its fruit yield. Subgynoecy represents a sex form with a high degree of femaleness and would have alternative use as gynoecy under limited resource conditions. Recently, many studies have been reported that QTL-seq, which integrates the advantages of bulked segregant analysis and high-throughput whole-genome resequencing, can be a rapid and cost-effective way of mapping QTLs. Segregation analysis in the F2 and BC1 populations derived from a cross between subgynoecious LOSUAS and monoecious BMB suggested the quantitative nature of subgynoecy in cucumbers. Both genome-wide SNP profiling of subgynoecious and monoecious bulks constructed from F2 and BC1 plants consistently identified three significant genomic regions, one on chromosome 3 (sg3.1) and another two on short and long arms of chromosome 1 (sg1.1 and sg1.2). Classical QTL analysis using the F2 confirmed sg3.1 (R2 = 42%), sg1.1 (R2 = 29%) and sg1.2 (R2 = 18%) as major QTLs. These results revealed the unique genetic inheritance of subgynoecious line LOSUAS through two distinct major QTLs, sg3.1 and sg1.1, which mainly increase degree of femaleness, while another QTL, sg1.2, contributes to decrease it. This study demonstrated that QTL-seq allows rapid and powerful detection of QTLs using preliminary generation mapping populations such as F2 or BC1 population and further that the identified QTLs could be useful for molecular breeding of cucumber lines with high yield potential.
We would like to thank Prof. Ki Whan Song for supplying cucumber inbred lines and Dr. Yong Suk Jung for his contribution in managing the data analysis.
Author Contribution statement
SL and KTW designed the research. KTW and CYZ developed the plant materials and performed field work and genetic analysis. KTW conducted the sequence data analysis and wrote the manuscript. RRS conducted statistical analysis. JHL, YK and CYZ conducted RNA expression-level analysis. All authors reviewed and approved this submission.
This work was supported by the Next-Generation BioGreen 21 Program (Plant Molecular Breeding Center No. PJ01329601) of Rural Development Administration, Republic of Korea.
Compliance with ethical standards
Conflict of interest
The authors declare no conflict of interest.
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