QTL Mapping of Parthenocarpy in Gynoecious Cucumber and Evaluation of a Marker Linked to a Major QTL

Parthenocarpy is an important trait for yield and quality of cucumber. However, the genetic and molecular mechanisms of parthenocarpy in cucumber were unclear. A two-season QTL study of parthenocarpy in cucumber was conducted with 145 F_2:3 families derived from a cross between EC1, a parthenocarpic inbred line and 8419, a non-parthenocarpic inbred line. Phenotypic data was evaluated based on percentage of parthenocarpy (numbers of parthenocarpic fruits/numbers of clipped female flowers). The data was collected 8-10 days after clipping all female flowers. A genetic linkage map spanning 808.1 cM in seven chromosomes with 133 SSR markers and 9 indel markers was constructed from an F₂ population of 145 plants. Seven QTLs were identified on chromosomes 1, 2, 3, 5 and 7. Parth2.1 on chromosome 2 was detected as a major-effect QTL in both spring and fall seasons, having LOD scores of 9.0, 6.2 and PVE of 17.4%, 10.2%, respectively. This QTL was further confirmed using a population derived from a RHL. Effectiveness of a peak marker of parth2.1 was clarified. The results of this study could unravel genetic mechanism of parthenocarpy in cucumber and the markers identified could be used in marker-assisted selection.