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- Author or Editor: Richard L. Lower x
Abstract
The title of this presentation might well have been either: Publish, Perish, Patent, Profit or Genetic Engineering: An Achilles Heel for Agricultural Research (7). References to academia in this discussion are specific to or encompass only public or land-grant institutions unless mention is made of privately endowed schools. It might be appropriate to define the role of land-grant institutions and then attempt to see if we are measuring up to land-grant philosophies as the gap is bridged between the exciting new biotechnology areas and state agricultural experiment stations. It is the latter that employ most of us.
Abstract
Plot size (number of hills) and seeding rate (SR) were evaluated for their effect on susceptibility of cucumber, Cucumis sativus L., seedlings screened for resistance to the striped and spotted cucumber beetles, Acalymma vittatum (Fabricius) and Diabrotica undecimpunctata howardi Barber, respectively. Susceptibility estimates were highest with single-hill plots in 1971 but there was no difference between 2 and 3 hills per plot in 1972. Plot sizes were significantly different only in degree of cotyledon damage. Six replicates appear satisfactory for field studies. SR may or may not influence susceptibility. Combined 1973-1974 data indicate that 15 seeds per hill may be practical for field studies.
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.
Abstract
Seed of four heterogeneous cucumber [Cucumis sativus (L.)] populations (C0-C3) that had undergone recurrent half-sib selection for improved germinability at 15°C were evaluated for seedling emergence and other horticultural characteristics under field conditions. Correlated responses to selection were observed for percent emergence 7 days after sowing and mean number of days to emergence. No correlated response to selection was observed for changes in sex expression, seedling vigor, or yield. These results suggest that selection for low temperature germinability at 15° did not result in any change in the horticulturally important characteristics monitored.
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.
Abstract
A heterogeneous cucumber (Cucumis sativus L.) population (mostly gynoecious) was evaluated at five locations for single-plant fruit yield at the mature-fruit stage in 1981. Seeds from the highest-yielding plants were then harvested, combined, and partitioned into five lots. Seeds were combined such that each location received only the superior genotypes from the other four locations. This procedure was continued for an additional four cycles using two types of selection: single-plant selection for fruit number at the mature-fruit stage (1981–82) and half-sib family selection at the once-over harvest stage (1983–84). In 1985, yield improvement from selection was measured by compositing the seeds of the selected plants or families from each of the four cycles and five locations and planting them at the five locations. No progress was made for total, marketable, or early yield. Percentage of culls was reduced an average of 0.7% per cycle. Genotype by environment interaction among the diverse locations may have prevented progress for yield.