Richard L. Lower, Todd C. Wehner and Samuel F. Jenkins Jr.
Todd C. Wehner, Samuel F. Jenkins Jr. and Richard L. Lower
Zhanyong Sun*, Richard L. Lower and Jack E. Staub
The incorporation of genes for parthenocarpy (production of fruit without fertilization) has potential for increasing yield in pickling cucumber (Cucumis sativus L.). The inheritance of parthenocarpy in cucumber is not well understood, and thus a genetic analysis was performed on F3 cross-progeny resulting from a mating between the processing cucumber inbred line 2A (P1, gynoecious, parthenocarpic, indeterminate, normal leaf) and Gy8 (P2, gynoecious, non-parthenocarpic, indeterminate, normal leaf). A variance component analysis was performed to fruit yield data collected at two locations (designated E-block and G-block) at Hancock, WI in 2000. The relative importance of additive genetic variance compared to dominance genetic variance changed across environments. The additive genetic variance was 0.5 and 4.3 times of dominance genetic variance in E-block and G-block, respectively. The estimated environmental variance accounted for ≈90% of the total phenotypic variance on an individual plant basis in both locations. Narrow-sense heritability estimated on an individual plant basis ranged from 0.04 (E-block) to 0.12 (G-block). Broad-sense heritability estimated on an individual plant basis ranged from 0.12 (E-block) to 0.15 (G-block). The minimum number of effective factors controlling parthenocarpy was estimated to range between 5 (G-block) to 13 (E-block). These results suggest that the response to direct selection of individual plants for improving parthenocarpy character will likely be slow and difficult. Experiment procedures that minimize the effect of environment on the expression of parthenocarpy will likely maximize the likelihood of gain from selection.
Todd C. Wehner, Paul C. St. Amand and Richard L. Lower
Jack E. Staub, Zhanyong Sun, Sang-Min Chung and Richard L. Lower
Cucumber (Cucumis sativus L. var. sativus; 2n = 2x = 14), has a narrow genetic base (3% to 8% polymorphism). Nevertheless, several genetic maps exist for this species. It is important to know the degree of colinearity among these maps. Thus, the positions of random amplified polymorphic DNAs, sequenced characterized amplified regions, simple sequence repeat, restriction fragment length polymorphisms, and fluorescent amplified fragment length polymorphism markers were compared in four maps. A previously unreported map was constructed in a narrow cross (processing line 2A × Gy8; C. s. var. sativus; ≈7% polymorphism) and compared with the three published maps [two narrow-based (processing type; C. s. var. sativus; 8% to 12% polymorphism) and a broad-based (C. s. var. sativus × C. s. var. hardwickii (R.) Alef. ≈12%)]. Common makers were identified in seven linkage groups, providing evidence for microsynteny. These common markers were used as anchor markers for map position comparisons of yield component quantitative trait loci. The relative order of anchor markers in each of six linkage groups (linkage groups 1, 2, and 4–7) that had two or more anchor markers within each group was colinear, and instances of microsynteny were detected. Commonalities in the position of some yield component quantitative trait loci exist in linkage groups 1 and 4 of the maps examined, and the general synteny among these maps indicates that identification and mapping of additional anchor markers would lead to successful map merging to increase cucumber map saturation for use in cucumber breeding.