title: Round fruit shape in WI7239 cucumber is controlled by two interacting quantitative trait loci with one putatively encoding a tomato SUN homolog.
abstract: QTL analysis revealed two interacting loci, FS1.2 and FS2.1, underlying round fruit shape in WI7239 cucumber; CsSUN , a homolog of tomato fruit shape gene SUN , was a candidate for FS1.2. Fruit size is an important quality and yield trait in cucumber, but its genetic basis remains poorly understood. Here we reported QTL mapping results on fruit size with segregating populations derived from the cross between WI7238 (long fruit) and WI7239 (round fruit) inbred cucumber lines. Phenotypic data of fruit length and diameter were collected at anthesis, immature and mature fruit stages in four environments. Ten major-effect QTL were detected for six traits; synthesis of information from these QTL supported two genes, FS1.2 and FS2.1, underlying fruit size variation in the examined populations. Under the two-gene model, deviation from expected segregation ratio in fruit length and diameter among segregating populations was observed, which could be explained mainly by the interactions between FS1.2 and FS2.1, and segregation distortion in the FS2.1 region. Genome-wide candidate gene search identified CsSUN, a homolog of the tomato fruit shape gene SUN, as the candidate for FS1.2. The round-fruited WI7239 had a 161-bp deletion in the first exon of CsSUN, and its expression in WI7239 was significantly lower than that in WI7238. A marker derived from this deletion was mapped at the peak location of FS1.2 in QTL analysis. Comparative analysis suggested the melon gene CmSUN-14, a homolog of CsSUN as a candidate of the fl2/fd2/fw2 QTL in melon. This study revealed the unique genetic architecture of round fruit shape in WI7239 cucumber. It also highlights the power of QTL analysis for traits with a simple genetic basis but their expression is complicated by other factors.
authors.affiliation: Horticulture College, Northwest A&F University, Yangling, 712100, China.|Horticulture Department, University of Wisconsin, Madison, WI, 53706, USA.
authors.forename: Yupeng
authors.initials: Y
authors.lastname: Pan
authors.affiliation: Horticulture College, Northwest A&F University, Yangling, 712100, China.
authors.forename: Xinjing
authors.initials: X
authors.lastname: Liang
authors.affiliation: Horticulture Department, University of Wisconsin, Madison, WI, 53706, USA.|College of Life Science, Agriculture and Forestry, Qiqihar University, Qiqihar, 161006, China.
authors.forename: Meiling
authors.initials: M
authors.lastname: Gao
authors.affiliation: Horticulture College, Northwest A&F University, Yangling, 712100, China.
authors.forename: Hanqiang
authors.initials: H
authors.lastname: Liu
authors.affiliation: Horticulture College, Northwest A&F University, Yangling, 712100, China.
authors.forename: Huanwen
authors.initials: H
authors.lastname: Meng
authors.affiliation: Horticulture Department, University of Wisconsin, Madison, WI, 53706, USA. yiqun.weng@wisc.edu.|USDA-ARS, Vegetable Crops Research Unit, 1575 Linden Drive, Madison, WI, 53706, USA. yiqun.weng@wisc.edu.
authors.forename: Yiqun
authors.identifier: http://orcid.org/0000-0001-9457-2234
authors.initials: Y
authors.lastname: Weng
authors.affiliation: Horticulture College, Northwest A&F University, Yangling, 712100, China. chengzh@nwsuaf.edu.cn.
authors.forename: Zhihui
authors.initials: Z
authors.lastname: Cheng
mesh_terms: D001483:Base Sequence; D002874:Chromosome Mapping; D003433:Crosses, Genetic; D018553:Cucumis sativus / Q000235:genetics*; D005638:Fruit / Q000033:anatomy & histology*; D017343:Genes, Plant; D008040:Genetic Linkage; D005819:Genetic Markers; D054643:INDEL Mutation; D018895:Microsatellite Repeats; D010641:Phenotype; D040641:Quantitative Trait Loci
chemical_list: D005819:Genetic Markers