QTL mapping of domestication and diversifying selection related traits in round-fruited semi-wild Xishuangbanna cucumber (Cucumis sativus L. var. xishuangbannanesis)

Authors: PAN, YUPENG - University Of Wisconsin; QU, SHUPING - University Of Wisconsin; BO, KAILIANG - University Of Wisconsin; GAO, MEILING - University Of Wisconsin; Haider, Kristin; Weng, Yiqun

Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/13/2017
Publication Date: 4/24/2017
Publication URL: http://handle.nal.usda.gov/10113/5700704
Citation: Pan, Y., Qu, S., Bo, K., Gao, M., Haider, K.R., Weng, Y. 2017. QTL mapping of domestication and diversifying selection related traits in round-fruited semi-wild Xishuangbanna cucumber (Cucumis sativus L. var. xishuangbannanesis). Theoretical and Applied Genetics. 130(7):1531-1548. doi: 10.1007/s00122-017-2908-2.

Interpretive Summary: Flowering time and fruit size are two important traits in domestication and diversifying selection in cucumber, but their genetic bases are not well understood. Here we reported QTL mapping results on flowering time and fruit size with F2 and F2:3 segregating populations derived from the cross between WI7200, a small fruited, early flowering primitive cultivated cucumber and WI7167, a round-fruited, later flowering semi-wild Xishuangbanna (XIS) cucumber. A linkage map with 267 microsatellite marker loci was developed with 138 F2 plants. Phenotypic data of male and female flowering time, fruit length and diameter and four other traits (mature fruit weight and number, hypocotyl length, and chilling tolerance of adult plants) were collected in multiple environments. Three flowering time QTL, FT1.1, FT5.1, and FT6.1 were identified; FT6.1 played the most important role in conferring less photoperiod sensitive early flowering during domestication whereas FT1.1 seemed more influential in regulating flowering time within cultivated cucumbers. Eight consensus fruit size QTL distributed in 7 chromosomes were detected, each of which contributed to both longitudinal and radial growth in fruit development. Among them, FS5.2 on chromosome 5 exhibited the largest effect on the determination of the round fruit shape characteristic of the WI7167 XIS cucumber. Possible roles of these flowering time and fruit size QTL in domestication of cultivated cucumber and crop evolution of the semi-wild XIS cucumber, as well as the genetic basis of round fruit shape in cucumber are discussed.

Technical Abstract: Flowering time and fruit size are two important traits in domestication and crop evolution in cucumber, but little is known about their genetic basis. In this paper, we reported QTL mapping on flowering time and fruit size inn populations derived from the cross between a small fruited, early flowering primitive cultivated cucumber line WI7200 and a round-fruited, later flowering semi-wild Xishuangbanna (XIS) cucumber line WI7167. A linkage map with 267 molecular markers was developed. Phenotypic data of male and female flowering time, fruit length and diameter and four other traits (mature fruit weight and number, hypocotyl length, and chilling tolerance of adult plants) were collected in multiple environments. Three flowering time were identified; the QTL FT6.1 on chromosome 6 played the most important role in conferring less photoperiod sensitive early flowering during domestication whereas FT1.1 on chromosome 1 seemed more influential in regulating flowering time within cultivated cucumbers. Eight consensus fruit size QTL distributed in 7 chromosomes were detected, each of which contributed to both longitudinal and radial growth in fruit development. Among them, FS5.2 on chromosome 5 exhibited the largest effect on the determination of the round fruit shape characteristic of the WI7167 XIS cucumber. Possible roles of these flowering time and fruit size QTL in domestication of cultivated cucumber and crop evolution of the semi-wild XIS cucumber, as well as the genetic basis of round fruit shape in cucumber are discussed.