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Donavon Sonnenberg, Patrick A. Ndakidemi, Ambrose Okem and Charles Laubscher

compared with the control. Table 1. Effect of drip irrigation on photosynthetic rate (A) between weeks 1 and 8 in Cucumis sativus . Table 2. Effects of drip irrigation on the transpiration rate (E) between weeks 1 and 8 in Cucumis sativus . Table 3

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Yiqun Weng, Shanna Johnson, Jack E. Staub and Sanwen Huang

Cucumber ( Cucumis sativus var. sativus L.) is an important and profitable processed vegetable product in many countries and a popular fresh market culinary component of human diets worldwide. In 2008, cucumber ranked fourth in total acres

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N.M.P. Guedes and P.H. Jennings

To improve somatic embryogenesis of Cucumis sativus, two types of explants (cotyledons and stem sections) were cultured on Murashige and Skoog (MS) media supplemented with 2,4-D (2.0 mg·L–1) + kinetin (0.5 mg·L–1). After 4 weeks, the embryogenic callus was transferred for 2 weeks to MS + NAA (1.0 mg·L–1) for embryo development. Stem sections failed to develop embryos while cotyledons responded with 14% embryo formation. The embryos were transferred to MS without hormones for 4 weeks to allow for plantlet growth. These embryos developed only shoots. To improve on the successful generation of embryos with root and shoot development, the procedures used above were repeated, but the cotyledons were cut into three sections to be used as explants. Each transverse section of the cotyledon was approximately 2–3 mm wide. All sections produced callus but not all of them were embryogenic. From the first section (cotyledon base), the second (between the first and third section) and the third section (furthest from the cotyledon base), respectively, 58%, 31%, and 5% embryo development occurred. Those embryos from the basal cotyledon sections regenerated 10 plantlets, 5 with shoots and roots and 5 with only shoots. Approaches to enhance somatic embryogenesis, and shoot and root development, will be discussed.

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Hybrid seed of cucumber (Cucumis sativus) is expensive to produce. Production of `artificial seeds' through somatic embryogenesis may be a viable alternative. Somatic embryos were induced, multiplied on a semisolid medium for 8-10 weeks, and germinated on agar-gelled medium before transplanting to soil. It was then important to determine the extent of variation among plants derived from somatic embryos. The criteria for variation among regenerants of cultivar Clinton were; plant height, fruit shape, fruit weight and number (yield/plant), days to first female flower and variation in selected isozymes. All measurements were taken on greenhouse-grown plants. Some regenerants of Clinton were also planted in the field and they flowered and, qualitatively, bore fruit as well as the zygote-derived plants. When quantitative measurements were made, variation was greater than for plants from zygotic embryos, but the visual impact was that there was little variation amongst regenerants. Regenerants grew more slowly and tended to yield higher numbers of slightly smaller fruits than plants from zygotic embryos. Average yield per plant was higher for somatic embryo-derived plants. For cultivar Corona only morphology of plant and fruit was examined. One plant was especially visually mutant and unacceptable as a commercial plant. The defects were readily identifiable in the seedling stage. Preliminary evidence suggests that `artificial seeds' of cucumbers may be a viable proposition.

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Hybrid seed of cucumber (Cucumis sativus) is expensive to produce. Production of `artificial seeds' through somatic embryogenesis may be a viable alternative. Somatic embryos were induced, multiplied on a semisolid medium for 8-10 weeks, and germinated on agar-gelled medium before transplanting to soil. It was then important to determine the extent of variation among plants derived from somatic embryos. The criteria for variation among regenerants of cultivar Clinton were; plant height, fruit shape, fruit weight and number (yield/plant), days to first female flower and variation in selected isozymes. All measurements were taken on greenhouse-grown plants. Some regenerants of Clinton were also planted in the field and they flowered and, qualitatively, bore fruit as well as the zygote-derived plants. When quantitative measurements were made, variation was greater than for plants from zygotic embryos, but the visual impact was that there was little variation amongst regenerants. Regenerants grew more slowly and tended to yield higher numbers of slightly smaller fruits than plants from zygotic embryos. Average yield per plant was higher for somatic embryo-derived plants. For cultivar Corona only morphology of plant and fruit was examined. One plant was especially visually mutant and unacceptable as a commercial plant. The defects were readily identifiable in the seedling stage. Preliminary evidence suggests that `artificial seeds' of cucumbers may be a viable proposition.

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Toshio Shibuya, Ryosuke Endo, Yuki Kitamura, Yoshiaki Kitaya and Nobuaki Hayashi

light with high R:FR light on the potential photosynthetic advantage of transplants, we investigated the photosynthetic light responses of cucumber ( Cucumis sativus L.) seedlings grown under fluorescent lamps with high R:FR light and compared them with

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Rebecca Grumet*, Xiaofeng Wang, Mohamed Tawfik and Mitch McGrath

Genomics tools have become increasingly varied and valuable for crop improvement. While several species have been targeted for concerted genomic efforts, the majority of horticultural species have received limited attention. Despite the wide variety of important cucurbit crop species, the Cucurbitaceae family has had minimal effort. We have initiated projects to develop genomic tools for cucumber, Cucumis sativus L. Efforts include production of cDNA, yeast two-hybrid, and genomic libraries, and development of an EST database and website for cucumber genomics. Sequences of cucumber leaf ESTs so far indicate that the cDNA library is of high quality and has modest redundancy. Distribution of sequences, as nominally predicted from GeneBank BLAST analysis, indicates that expressed genes fall in the following general categories: photosynthesis (21%), DNA/RNA/protein synthesis (20%), metabolism (15%), signaling (5%), other (16%), and unknown proteins (23%). Cucumber sequence data have been deposited into GenBank and are available on the Michigan State Univ. website (http://genomics.msu.edu/cucumberdb). The yeast two-hybrid library has been successfully used to identify and characterize several genes based on interaction with key proteins of interest, including genes interacting with viral replicases and poly(A) binding protein. The genomic library has been verified to be of high quality and has been used to identify clones of interest.

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Hurriah H. AL-Juboory

Gibberellic acid (GA3) promoted maleness and 2-Chloroethyl phosphonic acid (ethephon) promoted femaleness in cucumber (Cucumis sativus L.) cv Regal 446 seedlings when treated with water, ethephon (250 or 350 ppm) or GA3 (1000 or 2000 ppm) at the l-, 2-, or 3-leaf stage. Seedlings treated with ethephon at all stages produced more female flowers than those with water or GA3 treatments. GA3-treated seedlings produced significantly more male flowers than water treatments, at all developmental stages. The differential response of cucumber seedlings treated at different stages indicated the importance of timing growth regulator applications.

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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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Larry D. Knerr and Jack E. Staub

The available U. S. Cucumis sativus germplasm collection (754 Plant Introductions) was electrophoretically screened for genetic diversity using 39 enzymes representing a total of 57 loci. Polymorphisms were observed at 18 loci which included g2dh, gpi1, gpi2, gr1, gr2, idh, mdh1, mdh2, mdh3, mpi2, pep-la2, pep-pap2, per4, pgd1, pgd2, pgm1, pgm3, and skdh. Appropriate crosses were set up to verify the inheritance of and test linkages among these loci. Four allozyme linkage groups have currently been identified. Representative linkages and their genetic distances include: gpi1 - mdh3 (20); pgm1 - pgd1 (25); and g2dh - pgd2 (19). Additionally, crosses were made to marker stocks to test for linkages between some allozyme loci and loci coding for resistance to downy mildew and anthracnose, long hypocotyl, divided leaf, short petiole, glabrous, compact plant, determinate, little leaf, and bitter free (bi).