Search Results
Twenty-eight greenhouse screening materials, with predetermined airflow resistance values, were evaluated for exclusion of silverleaf whitefly (Bemisia argentifolii Perring & Bellows) and thrips from a mixed-species population. Screens differed in exclusion efficacy, as a percentage of the fiberglass window screen control and at an approach velocity of at 92 m/min, from –35 to 94% for silverleaf whitefly and from –13 to 95% for thrips. Seventeen screens excluded more silverleaf whitefly, whereas seven excluded more thrips than the window screen control. One material differentially excluded whitefly over thrips; many more differentially excluded thrips over whitefly. Airflow resistance, indicative of mesh hole size, did not necessarily correspond with degree of exclusion. Though two high-resistance screens, No-Thrips and Econet S, excluded both pests, not all materials characterized as highly resistant to airflow provided significant exclusion. Exclusion of both pests was also attained with three moderate resistance screens, BugBed 123, BugBed 85, Pak 44×44, and one low-resistance screen, BugBed 110UV.
Abstract
An array of 102 single and 3-way cross hybrids of pickling cucumbers (Cucumis sativus L.) were evaluated for yield over 2 years under field conditions. Hybrids were produced by crossing lines with gynoecious, monoecious, hermaphroditic, and androecious expression. The significant correlations between femaleness (percent pistillate nodes) and marketable yield were 0.34 for single cross and 0.45 for 3-way cross hybrids. Highest yields were obtained from the single crosses of gynoecious × androecious, and gynoecious × hermaphrodite, followed by the 3-way cross of (gynoecious × hermaphrodite) × androecious, on the basis of either total or marketable fruits per plant. Hybrids having androecious pollen parents exhibited more femaleness and produced higher yields than those with monoecious pollen parents. The possible use of these high yielding parental sex combinations as hybrid cultivars in place of conventional single crosses (gynoecious × monoecious) might improve the production of pickling cucumbers for once-over mechanical harvest.
Abstract
Differences in response of carrot (Daucus carota L.) to northern root-knot nematode (Meloidogyne hapla Chitwood) were demonstrated when grown in muck soil, under naturally infested field conditions. Significant differences among cultivars for galling, forking, and fasciculation were noted, but no significant difference was noted for stubbing. A tolerance index (Ti) was calculated by numerically combining the effects of each response to compare the total reaction of the carrot cultivars to M. hapla.‘ Spartan Classic’ was the most tolerant; whereas Danvers 126’ was the least tolerant to M. hapla.
Abstract
Hybrids from single and 3-way crosses involving gynoecious, hermaphroditic, monoecious, and androecious parent lines of cucumber (Cucumis sativus L.) were grown for 2 summers near East Lansing, Michigan. Frequencies of gynoecious hybrid plants varied significantly between years for most crosses. The femaleness (% gynoecious plants) of most single cross hybrids from gynoecious × androecious crosses was greater than ‘Pioneer’ for 1973 but not as clear-cut in 1974. The same differences were observed for 3-way crosses derived from gynoecious-hermaphroditic F1 seed parents crossed with an androecious pollen parent The differences were more marked for 1973 than 1974. However, when the femaleness of 3-way hybrids derived from the same F1 seed parents crossed with either androecious or monoecious pollen parents were compared, the androecious crosses were consistently more female. Overall, hybrids derived from androecious pollen parents were as highly female, or more so, than hybrids derived from monoecious pollen parents including hybrid ‘Pioneer’.
Abstract
Methyl-2-chloro-9-hydroxyfluorene-(9)-carboxylate (chlorflurenol) effectively promoted parthenocarpic fruit development in gynoecious pickling cucumbers, Cucumis sativus L. Treatment with chlorflurenol increased yields of fruits under both greenhouse and open-field conditions. Yields were dependent on the degree of genetic parthenocarpy for each cultivar. Parthenocarpic yields following chlorflurenol treatment were higher with night temperatures of 16° and 21°C than with 27°.
Abstract
The hybrids and segregating populations obtained by crossing 4 gynoecious with 4 androecious lines were analyzed to determine the inheritance of sex expression in dioecious cucumber (Cucumis sativus L.). Sex expression of all F1 hybrids was characterized by plants with a continuous pistillate stage of flowering on the main stem. This included both gynoecious and predominantly female plants. No reciprocal cross differences were observed in the F1 and backcross generations. Backcrosses to the gynoecious parents produced plants with a continuous female stage. Backcrosses to the androecious parent produced plants with continuous pistillate, monoecious (without a continuous pistillate stage), and androecious expression in a 2:1:1 ratio, respectively. The F2 generation segregated 12:3:1 continuous pistillate, monoecious, and androecious phenotypes, respectively. Two major loci, a and acr, with epistasis are proposed to control sex expression. The a locus permits male (aa) as opposed to female (A –) flower expression. The acr locus conditions the intensity of femaleness.
Abstract
Gynoecious F3 lines of cucumber ( Cucumis sativus L.) selected for multiple-pistillate (MP) flowers per node, were tested for yield potential in the greenhouse and field. In the greenhouse tests, MP lines gave more fruits per plant and higher yields than F1 hybrids. In field tests, MP lines yields were equivalent to commercial hybrids. The good performance of MP lines when compared to adapted hybrids suggests that multiple-pistillate flowering may be a valuable character for increasing yields with once-over harvest systems.
Abstract
From progenies of crosses between 2 multi-pistillate (MP) and 2 single-pistillate (SP) gynoecious pickling cucumber (Cucumis sativus L.) cultivars, it was determined that MP is recessive to SP expression. Genetic analyses suggested that one major gene with several modifying factors affect this character. The gene symbol proposed for multipistillate expression is mp.
Abstract
Progenies of crosses between pickling cucumber (Cucumis sativus L.) lines SC 601 H and MSU 381 were evaluated to determine the inheritance of mature fruit carpel separation. Reciprocal cross differences for carpel separation were not detected. Weak carpel sutures, expressed by carpel separation, exhibited dominance over non-separation. Additive genetic variance exceeded dominance variance, and a significant non-genetic (environment) component of variation was observed. Estimates of narrow-sense heritability ranged from 39 to 45% suggesting that carpel suture strength, and consequently fruit quality, could be improved through rigorous selection at fruit maturity. A specific genetic model consistent with the observed frequency distributions was not proposed, but tests indicated the data might be interpreted as a 2 or 3-gene system. In populations segregating for sex expression, high frequencies of carpel separation were not associated with gynoecious or any one sex expression phenotype.
Abstract
Pyrazon (5-amino-4-chloro-2-phenyl-3(2H)-pyridazinone) was readily metabolized to the N-glucosyl derivative of pyrazon (N-2-chloro-4-phenyl-3(2H)-pyridazinone glucosamine) in red beet (Beta vulgaris L. cv. Detroit Dark Red), but there was no metabolism of pyrazon in the 8 susceptible species examined. In leaf discs from 9 inbred lines of red beet, the percent conversion of pyrazon to the N-glucoside ranged from 44% to 76% after 10 hr. In 2 lines of red beet treated with 2 concentrations of pyrazon in nutrient culture, there was a direct relationship between the rate of pyrazon metabolism and plant tolerance.