Quantitative trait locus analysis of cucumber fruit texture using double‐digest restriction‐site‐associated DNA sequencing

Fruit firmness and crispness are important traits of cucumber because they directly affect its commercial value. We performed quantitative trait locus (QTL) analysis of these fruit texture traits with the double-digest restriction-site-associated DNA sequencing (ddRAD-Seq) technique and detected 31 QTLs for fruit firmness: 11 for placenta firmness, 12 for skin firmness, and 8 for flesh firmness; and 25 QTLs for crispness-related scores: 10 for flesh crispness index, 8 for flesh apparent fractal dimension by Richardson plot, and 7 for flesh apparent fractal dimension by box-counting (Kolmogorov’s dimension). Several QTLs associated with flesh firmness and crispness are located near regions for fruit length, diameter, and length-to-diameter ratio, and for resistance to powdery mildew and downy mildew, indicating that gene linkage is likely to limit breeding efficiency. Our results will contribute to the development of informative DNA markers closely linked to genes for desirable fruit texture traits that are required for effective selection of new cultivars.