Quantitative trait loci for fruit size and flowering time-related traits under domestication and diversifying selection in cucumber (Cucumis sativus)

Authors: SHENG, YUNYAN - Heilongjiang Bayi Agricultural University (HLAU); PAN, YUPENG - University Of Wisconsin; YUHONG, LI - Northwest A&f University; YANG, LUMING - University Of Wisconsin; Weng, Yiqun

Submitted to: John Wiley Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/17/2019
Publication Date: 9/30/2019
Citation: Sheng, Y., Pan, Y., Yuhong, L., Yang, L., Weng, Y. 2019. Quantitative trait loci for fruit size and flowering time-related traits under domestication and diversifying selection in cucumber (Cucumis sativus). John Wiley Journal. 139:176-191. https://doi.org/10.1111/pbr.12754.
DOI: https://doi.org/10.1111/pbr.12754

Interpretive Summary: Modern cucumber was domesticated from the wild progenitor, Cucumis sativus. var. hardwickii. The genetic basis of domestication related traits in cucumber is not well understood. We conducted QTL mapping of flowering time and fruit size and weight-related traits with recombinant inbred line and F2 populations derived from the cross between the cultivated cucumber line Gy14 and the wild cucumber line WI7221. Phenotypic data of first female flowering time (FFT), mature fruit length (MFL) and diameter (MFD), fruit number (FN) and weight (FW), as well as 100-seed weight (SW) were collected in multiple environments. Twenty-four QTL were detected including 2 for FFT, 3 for FW, 4 for MFD, and 5 each for MFL, FN and SW. The major-effect QTL fft1.1 seemed to be the key player in regulating flowering time in cultivated cucumber whereas the minor-effect QTL fft6.3 contributed to less photoperiod sensitive early flowering during domestication. Most of the fruit size and weight QTL were co-localized on chromosomal regions that also harbor QTL detected in previous studies using populations derived from crosses between cultivated cucumbers. This may suggest that these fruit size QTL may be under selection during both initial domestication and subsequent crop evolution of cucumber. The possible roles of the identified QTL in domestication and diversifying selection of cucumber were discussed. Results from this study also suggested that the wild cucumber is a useful resource for capturing positive transgressive segregation and novel alleles that could be explored in cucumber breeding.

Technical Abstract: Cucumber was orginated in India and sorroudning regions and its wild progenitor is Cucumis sativus. var. hardwickii. The genetic basis of domestication related traits in cucumber is not well understood. We conducted QTL mapping of flowering time and fruit size and weight-related traits in two segregating populations derived from the cross between the cultivated cucumber line Gy14 and the wild cucumber line WI7221. Phenotypic data of first female flowering time (FFT), mature fruit length (MFL) and diameter (MFD), fruit number (FN) and weight (FW), as well as 100-seed weight (SW) were collected in multiple environments. Twenty-four QTL were detected. The major-effect QTL fft1.1 seemed to be the key player in regulating flowering time in cultivated cucumber whereas the minor-effect QTL fft6.3 contributed to less photoperiod sensitive early flowering during domestication. Most of the fruit size and weight QTL were co-localized on chromosomal regions that also harbor QTL detected in previous studies using populations derived from crosses between cultivated cucumbers. This may suggest that these fruit size QTL may be under selection during both initial domestication and subsequent crop evolution of cucumber. The possible roles of the identified QTL in domestication and diversifying selection of cucumber were discussed. Results from this study also suggested that the wild cucumber is a useful resource for capturing positive transgressive segregation and novel alleles that could be explored in cucumber breeding.