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J.E. Staub and V. Meglic

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.

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J. E. Staub and Jinsheng Liu

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.

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E. V. Wann and J. E. Staub

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.

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F. Kultur, H.C. Harrison and J.E. Staub

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.

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F. Kultur, H.C. Harrison and J.E. Staub

Muskmelon (Cucumis melo L.) genotypes, Birdsnest 1 [`Qalya' (BN1)], Birdsnest 2 (BN2), and `Mission' (V) were used to determine the effects of 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 the Hancock (sandy soil, <1% organic matter) and Arlington (heavy, praire loam soil, >4% OM) Experimental Farms in Wisconsin. 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 row 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, fruit number per hectare, average fruit weight, yield (g) per plant, yield (MT) per hectare, and fruit sugar concentration. All genotypes produced higher yield, fruit number and sugar concentration on the mineral soil at Arlington compared to the sands at Hancock. The main effect of genotypes was significant for all traits examined. BN1 and V genotypes had greater yield (gram per plant, yield per hectare, and average fruit weight) as well as higher fruit quality (fruit sugar concentration) than the BN2 genotype. Spacing affected all traits examined except primary branch number and fruit sugar concentration. As withinrow spacing increased from 35 to 70 cm, fruit number per plant, yield per plant and average fruit weight increased. However, yield (MT) per hectare and fruit number per hectare decreased. Fertility was adjusted according to soil tests for the two different soil types at the two farm locations.

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Jack E. Staub, Larry D. Knerr and Herbert J. Hopen

The growth and yield of three cucumber (Cucumis sativus L.) genotypes were evaluated in 1987 and 1988 using three planting arrangements and four weed control treatments. A monoecious, indeterminate, normal leaf cultivar, Calypso, a gynoecious, normal leaf size determinate × monoecious determinate F1 hybrid (UW 11234), and a gynoecious, determinate little leaf inbred line (WI 50476) were evaluated for fruit yield at a 30-cm equidistant (109,000 plants/ha), a 20-cm equidistant (242,000 plants/ha), and a 43-cm row (272,000 plants/ha) spacing. Weed control treatments consisted of an unweeded control, naptalam benzoic acid at 6.7 kg ae/ha, chloramben at 4.5 kg ae/ha, and the herbicides in combination. Although number and weight of fruit per hectare increased with increasing plant density, fruit weight per plant decreased with increasing density. Fruit harvested from plants in unweeded control plots were significantly smaller than those in herbicide-treated plots, and fruit yield of unweeded control plots was lower than in nonweedy plots in 1987. In 1987, plants in plots treated with naptalam produced smaller fruit than plants in plots treated with chloramben or chloramben plus naptalam. Although fruit yield per plant in 1987 was similar in chloramben plots with or without naptalam and generally higher than that of plots treated only with naptalam, fruit yields from naptalam-treated plants were highest in 1988. `Calypso' usually produced more and larger fruit than the determinate genotypes. Based on comparisons of fruit per plant under comparable spacings, productivity of WI 5047G was often lower and its fruit were smaller than those of normal leaf genotypes. Plants of WI 5047G may not attain the source capacity needed for adequate fruit growth before the onset of anthesis, thus producing smaller fruit. Chemical names used: (2-[(1-naphtalenylamino)carbonyl)benzoic acid (naptalam); 3-amino-2,5dichlorobenzoic acid (chloramben).

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Todd C. Wehner, J.S. Liu and Jack E. Staub

A second gene for bitterfree foliage in cucumber (Cucumis sativus L.) was discovered. In a cross between two inbred lines having bitterfree foliage (NCG-093 and WI2757), the F1 progeny were bitter, the F2 progeny segregation frequency fit a ratio of 9 bitter : 7 bitterfree, and the BC1 segregation frequencies fit a ratio of 1 bitter : 1 bitterfree. Thus, a second factor nonallelic to the previous bitterfree gene, bi, controls the bitterfree trait. When F2 and BC1 progeny resulting from crosses of bitterfree NCG-093 with other bitter lines were studied, the second factor for bitterfree in NCG-093 fit a recessive, single-gene model. The existence of a second, recessive bitterfree gene was confirmed in additional crosses, and the gene was designated bi-2. Further analysis of two crosses indicated that bi-2 was linked with the short petiole (sp) gene (map distance = 11 cM).

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Jack E. Staub, Clinton E. Peterson, Linda K. Crubaugh and Mary J. Palmer

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V. V. Meglic, T. F. Horejsi, J. E. Staub and J. D. McCreight

The genetic diversity of 400 U.S. melon germplasm plant introductions was assessed using 35 enzyme systems. Polymorphisms were observed at 24 putative loci (Ac, Acp1, Acp4, Ak2, Ak3. Ak4, Fdp1, Fdp2, Fdp4, Gpi, Idh, Mdh2, Mdh4, Mdh5, Mdhb, Mpi1, Mpi2, Pgd1, Pgd2, Pgm, Pep-g1, Pep-1a, Pep-pap, Skdh) representing 17 different enzymes. Sixteen loci demonstrated simple Mendelian inheritance. Multivariate analyses aided in reduction of data using 16 loci and linkage relationships were observed among the plant introductions. Two of 16 loci (Pgd1 and Acp1) segregated independently. Fourteen loci were assigned into three linkage groups (A-C): A Fdp1, Fdp2, Acp4, Skdh; B Mdh2, Mdh4, Mdh5, Mdh6, Pep-g1, Pgm; C Mpi2, Ac, Idh.