Search Results
Research was conducted to determine the reliability of several techniques for measuring the response of cucumber to low-moisture stress. Low and high moisture stress levels were imposed in field plots by differential irrigation. Plots under low stress (high soil moisture) had a mean tensiometer reading of 9±1.0 cb during the evaluation period, and plots under high stress had a mean tensiometer reading of 37±2.3 cb. Six genotypes of diverse backgrounds were evaluated for their stress response. The drought-tolerant cultivars `Alagi', W142121, and WI1983LL (Little Leaf) showed least response to the imposed stress. Visual ratings and stress index were correlated with moisture stress levels and they detected differences in stress response among cultivars. Plant water content, stomatal conductance, and transpiration rate were least reliable for measuring moisture stress. Visual ratings appeared to be as reliable as the other more quantitative types of measurements for detecting stress tolerance.
The genetic diversity among Cucumis sativus var. sativus (commercial cucumber) (1), var. anatolicus (2), var. cilicicus (3), var. europaeus (4), var. falcatus (5), var. indo-europaeus (6), var. irano-turanieus (7), var. izmir (8), var. sikkimensis (9), var. squamosus (10), var. testudaceus (11), var. tuberculatus (12), var. vulgatus (13), and var. hardwickii (14) were assessed using 7 morphological characteristics and 9 isozyme loci to determine their potential use for plant improvement. Results of morphological comparison below. Isozyme and morphological analysis did not result in similar dendrogram depictions. Varieties 13 and 3 might have potential in plant improvement based on yield performance.
Scientific disagreement about criteria for accurate classification of similar, if not seemingly identical, cultivars has led to spirited debate in legal and agricultural communities. The lack of universally acceptable working definitions of functional genetic distance and difference, as well as insufficient data on genetic diversity, has made it difficult to define a legal framework for cultivar discrimination. In order to satisfy the “distinctness” criterion during plant patenting, genetic diversity and difference must be described unequivocally in measurable terms. Moreover, the number of markers or other characteristics needed to identify the “nonobvious” nature of the cultigen will determine the breadth of protection under the patent. Increasingly, patent examiners must interpret novelty and distinctness in terms of molecular as well as gross phenotypic (flower color, plant habit, etc.) information. A description of difference using molecular markers may be more difficult compared to a description of function (i.e., how many markers are required to assign difference). Consequently, the effective use of molecular marker information in the legal community will require scientific agreement on the meaning of genetic distance as it relates to genetic difference.
Abstract
Four sets of nearly isogenic bacterial wilt [Erwinia tracheiphila (E.F. Smith)] Holland resistant and susceptible gynoecious cucumber (Cucumis sativus L.) lines, along with their companion segregating generations were evaluated under replicated field conditions for flowering date, fruit quality, fruit number, and length : diameter ratio (L:D). In addition to flowering earlier, susceptible lines were higher-yielding and had longer fruits than their resistant counterparts. Although differences in fruit quality were not significant, susceptible lines were preferred by a panel of seven judges. Compared to susceptible lines, hybrid progeny were later-flowering and in some instances lower-yielding.
Abstract
‘Wautoma’ (Fig. 1), a multiple-disease resistance, monoecious-processing cucumber (Cucumis sativus L.) inbred, was released 19 Feb. 1984 by the USDA. Currently available monoecious varieties are not suitable for blending with some of the new hybrids that have multiple-disease resistance and bitter-free fruits. ‘Wautoma’ is recommended for use as a pollinator to blend with seed of multiple-disease resistant hybrids, and as a pollen parent in hybrid development. In 1983 and 1984, it was tested in observational and processing trials under breeding line number WI 1902M.
Abstract
Hybrid and BC1 progenies from crosses among 3 inbred lines of Cucumis sativus var. sativus and 3 C. sativus var. hardwickii collections were evaluated for days to first flower, sex expression, leaf area of the 4th leaf, fruit length, diameter, length/diameter ratio, and number of fruit per plant. No consistent reciprocal differences were observed, suggesting lack of cytoplasmic and/or maternal control over these traits. F1 data reflected the dominance of var. sativus parental genes for days to first flower, leaf area of the 4th leaf, and the dominance of hardwickii genes for fruit number. Rate of progression towards the sativus recurrent parent for days to first flower, leaf area of the 4th leaf, fruit length, diameter, and number was rapid, approaching sativus characteristics in BC1. Atypical sex expression segregations in the BC1 may be associated with sex modifying genes which may govern daylength response.
Abstract
Cucumber (cucumis sativus L.) hybrids from crosses with 3 female (gynoecious) parents and 2 genetically similar male parents were evaluated at 3 locations to determine if bisexual (phenotypically andromonoecious) parents can be used in hybrid cultivars with no loss in yield or quality. Bisexual parents developed through 8 backcrosses to recurrent gynoecious lines produced hybrids that could not be distinguished from those obtained by using silver nitrate-induced, near-isogenic gynoecious pollen parents. Yield, fruit shape, defects, brining quality, and sex expression of hybrids from the 2 near-isogenic pollen parents were not significantly different. Deficiencies generally attributed to bisexual parents were corrected with adequate backcrossing to establishing bisexual lines.
Abstract
Seeds from three cycles of recurrent selection in a heterogeneous cucumber (Cucumis sativus L.) population for improved percentage of germination at 15°C were subjected to five treatments and evaluated for percentage of emergence and average number of days to emergence at 15°, 20°, and 25° under controlled conditions. Treatments included dry seed, imbibed seed, and pregerminated seed in combination with a supporting gel at sowing. Results indicate that the mechanism for improved low temperature germination is not due to enhanced imbibition. Data also suggest that the percentage of emergence of imbibed seed with or without gel is complemented by the genetic potential to germinate at low temperatures and that no such complementation exists for pregerminated seed. Percentage of emergence of dry and imbibed seed with or without gel at 15° was improved while selecting only for improved germination at 15°, indicating a correlated response to selection.
Abstract
Recurrent half-sib selection within a heterogeneous population of cucumber (Cucumis sativus L.) was effective in improving germination at 15°C from 34.4% in cycle 0 to 92.4% in cycle 3. The linear regression coefficient indicated an average increase of 19.8% units per cycle of selection. Correlated responses to selection resulted in increased percentage of germination at 20° and 25° and decreased days to germination at 15°, 20°, and 25°.
Muskmelon (Cucumis melo L.) genotypes, Birdsnest 1 [`Qalya' (BN1)], Birdsnest 2 (BN2), and `Mission' (V) were used to determine the effects of differing plant architecture and spacing on fruit sugar concentration and yield. The BN1 and BN2 genotypes possessed a highly branched growth habit specific to birdsnest melon types, but not characteristic of standard indeterminate vining types (e.g., `Mission'). Experiments were conducted at both the Hancock and Arlington Experimental Farms in Wisconsin, where plant response to two within-row spacings [35 cm (72,600 plants/ha) and 70 cm (36,300 plants/ha)] in rows on 210-cm centers was examined. Genotypes were grown in a randomized complete-block design with four replications at each location and evaluated for primary lateral branch number, fruit number per plant and per hectare, average fruit weight, yield per plant (g), yield per hectare (t), and fruit sugar concentration. Yield, fruit number, and sugar concentration were higher for all genotypes at Arlington than at Hancock. The main effect of genotype was significant for all traits examined. Genotypes BN1 and V had higher mean fruit weight, yield per plant and per hectare, and fruit quality (fruit sugar concentration) than did BN2. Spacing affected all traits, except primary branch number and fruit sugar concentration. Fruit number and yield per plant and average fruit weight were higher with wider spacing, but yield (t·ha-1) and fruit number per hectare were lower.