Cucumber (Cucumis sativus L.) is an economically important vegetable crop cultivated worldwide. Plant architectural traits, such as lateral branch number (LBN), vine length (VL), number of nodes (NN) and internode length (IL), may directly influence production practices, plant performances, fruit yield and quality. Despite their importance, investigation on the genetic basis of these traits in cucumber is limited. In this study, we conducted QTL mapping for VL, NN, IL and LBN using bi-parental F2, F2-derived F3 and recombinant inbred line (RIL) populations. There are significant positive correlations between LBN, VL and NN. Estimated board-sense heritability using entry-mean basis of the RIL population was high, ranging from 0.66 to 0.84. Two linkage maps were developed through genotyping-by-sequencing of 140 F2 individuals and Diversity Arrays Technology (DArTag) SNP genotyping of 135 RIL, containing 1912 and 334 SNP loci in seven linkage groups and spanning 1077 and 948 cM, respectively. QTL mapping analysis detected a total of 79 QTLs associated with the four traits in six environments or populations. Based on their physical locations, 66 QTLs were distributed in ten QTL clusters harboring four major-effect and six minor-effect QTLs. Each of the major- and minor-effect QTLs was supported by consistent and reproducible detection from at least three environments. Notably, major-effect QTLs for VL, NN and LBN were co-localized in two genomic regions on Chr1 (3.73 Mbp) and Chr6 (3.78 Mbp), and the major-effect QTL for IL was mapped in a 3.98-Mbp region on Chr5. These findings provide a framework for dissecting the genetic architecture of these complex traits, and valuable genetic information for cucumber breeders to employ molecular-assisted breeding approaches and develop improved varieties with enhanced productivity.
