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  • Author or Editor: Todd C. Wehner x
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Abstract

Compressed air was injected into fruit of pickling cucumber (Cucumis sativus L.) to simulate the build-up of gas during brining. Four size grades were tested from 4 cultivars over 2 harvests and 2 seasons. Carpel adhesion, as measured by the air pressure required to separate the carpels, was negatively correlated with fruit size. Higher air pressure was required to separate the carpels of cultivars resistant to balloon bloating. The formation of balloon bloaters in cucumbers brined in commercial tanks was correlated with results from the compressed air test of carpel adhesion, especially with fruit 45 to 51 mm in diameter.

Open Access

Abstract

Hypocotyl and cotyledon expiants of 85 cultivars and lines of cucumber were screened for adventitious shoot and root formation in tissue culture. Tissue was cut from 7-day-old seedlings and grown on a medium consisting of Murashige-Skoog salts and vitamins with 1 mg/liter each of 6-ben-zylamino purine (BA) and naphthaleneacetic acid (NAA), and 3% sucrose added. No shoots were formed from hypocotyl pieces, while 28 of the 85 lines formed shoots from cotyledon tissue. Thirty-two lines formed at least one root in culture, and there was no difference in the frequency of root formation between cotyledon and hypocotyl tissue. There was no correlation between root and shoot formation. The best 2 lines, PI 279463 and PI 401732, had 53% and 40% of the cotyledon pieces forming shoots, respectively.

Open Access

Abstract

The rate of natural outcrossing in cucumber (Cucumis sativus L.) was measured at 3 locations in North Carolina, using the dominant allele for scab resistance as the marker gene. Outcrossing was measured within and between 1.5 m plots in isolation blocks. Between-row outcrossing averaged 36% over the 3 locations, and within-row outcrossing averaged 17%. Self-pollination accounted for 47% of the pollinations. Results suggest that populations should be intercrossed either as single plants, or in family rows treated with growth regulators to control pollen flow and prevent sib- and self-pollination.

Open Access

Cultigens frequently are tested for eventual monoculture production conditions in trials with different cultigens in adjacent rows. We determined the effect of using different cultigens of pickling and fresh-market cucumber (Cucumis sativus L.) in bordered (three-row) and unordered (l-row) plots. Cultigens contrasted in characteristics important in competitive effects: plant architecture (tall vs. dwarf), anthracnose resistance (susceptible vs. resistant), and sex expression (monoecious vs. gynoecious). In all four test years, there was no significant interaction of border with center row in unordered vs. bordered plots, with three exceptions: there was a significant reduction in yield of M 21 in 1982 when bordered by `Calypso' (a large-vined genotype), and a reduction in yield of `Southern Belle' in 1984 when bordered by `Calypso' or SMR 58. In most cases, there was an increase in yield if the border genotype had short vines. We concluded that. in most cases, trials can be run using unordered plots without significant effect or yield.

Free access

Understanding the natural mating behavior (self- or cross-pollination) in watermelon is important to the design of a suitable breeding strategy. The objective of this study was to measure the rate of self- and cross-pollination in watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai] using the dominant gene Sp (Spotted leaves and fruit) as a marker. The experiment consisted of two studies and was a split plot in a randomized complete block design with 3 years (2009 to 2011) and four locations (Clinton, Kinston, Oxford, Lewiston, NC). For the intercrossing study, whole plots were the two spacings (1.2 × 0.3 m and 1.2 × 0.6 m) with four replications in 2010. For the inbreeding study, whole plots were two equidistant spacings (3 × 3 m and 6 × 6 m) with four replications in 2009 to 2011. Cultivars Allsweet and Mickylee were subplots within each whole plot. In the inbreeding study, spacing and year had a significant effect on the rate of self-pollination, which was moderate (47% and 54%, respectively) when watermelon plants were trained in a spiral and spaced 3 × 3 m or 6 × 6 m apart. Spacing and cultivar did not have a significant effect on cross-pollination in the intercrossing study. Closely spaced watermelon plants (1.2 × 0.3 m and 1.2 × 0.6 m) had low natural outcrossing rate (31% and 35%, respectively) and was not adequate to intercross families. However, breeders should consider the amount of self-pollination in watermelon to calculate the estimates of component of genetic variances.

Free access

Two studies were conducted to test the effects of various tissue culture media on somatic embryogenesis from cotyledon tissue of cucumber (Cucumis sativus L.). The two best media for embryo initiation were Murashige and Skoog (MS) salts and vitamins containing either 1 or 2 mg 2,4-D/liter and 0.5 mg kinetin/liter. In the second study, embryos developed more normally. More plantlets developed when tissue was removed from the initiation medium after 3 weeks and transferred to MS containing 1 mg NAA/liter and 0.5 mg kinetin/liter for 3 weeks, rather than leaving the embryos on a medium containing 2,4-D. Histological evidence indicated that the embryos were multicellular in origin. Charcoal in the maturation medium inhibited embryo development. Chemical names used: (2,4-dichlorophenoxy) -acetic acid (2,4-D); N-(2-furanylmethyl)-lH-purine-6-amine (kinetin); 1-naphthaleneacetic acid (NAA).

Free access

Salted and sweet watermelon rind pickles are commonly produced in North America, Europe, and Asia using traditional recipes. Homeowners and small industries use the leftover watermelon crop, especially from cultivars having thick and crisp rind, to produce pickles. Recently, we classified rind thickness for a set of obsolete and heirloom cultivars used by home gardeners and heirloom collectors in the United States. In this study, we used elite cultivars for growers interested in high yield, fruit quality, adaptability, and disease resistance. The objective of this study was to classify modern cultivars (nine inbreds and 103 F1 hybrids) of watermelons available to growers for use in production of watermelon rind pickles. Based on the data, cultivars were divided into three groups of rind thickness and categorized according to pedigree (inbred or F1 hybrid), fruit type (seeded or seedless), and flesh color (red, orange, or yellow). Most of the cultivars tested (109 of 112) had rind thicker than 10 mm and could be used for pickle production.

Full access

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).

Free access

Combining the use of PCR and single-strand conformation polymorphisms (SSCP), nine sequences from the cucumber genome were successfully identified and cloned that encoded two well-conserved asparagine-proline-alanine (NPA) domain homologues to aquaporin genes. The sensitivity and detection efficiency of SSCP and restriction enzyme analysis for detecting DNA sequence variation were evaluated using similar-sized DNA fragments. The SSCP analysis was more sensitive and efficient for discriminating different clones than restriction enzyme analysis, although some sequence variation inside similar-sized DNA fragments could be identified by restriction analysis. Consideration of the results of SSCP analysis with DNA sequence information indicated that one or two base pair changes in the amplified regions could be detected. Moreover, the SSCP analysis results of genomic DNA PCR products that were amplified by degenerate primers can provide rough information about the number of member genes. If the SSCP bands of a cloned fragment (such as CRB7) did not have the corresponding bands from genomic DNA PCR products, that fragment might be a misamplified product. The PCR-based SSCP method with degenerate oligonucleotide primers should facilitate the cloning of member genes.

Free access