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  • Journal of the American Society for Horticultural Science x
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Brushing (40 strokes per 1.5 minutes, twice daily) or moisture stress conditioning (MSC) (daily nonlethal dry-down cycles) reduced seedling growth of two cucumber (Cucumis sativus L.) cultivars in 1991 and three squash (Cucurbita pepo L.) cultivars in 1991 and 1992. In both years, watermelon [Citrullus lanatus Thunb. (Matsum. & Nakai)] cultivars varied in responsiveness to brushing; brushing reduced stem length 0% to 44% over four cultivars in 1992. MSC reduced growth of all cultivars. Brushing increased the rate of water loss from detached leaves of cucumber, squash, and watermelon, whereas MSC decreased water loss from leaves of cucumber and squash. In 1991, under well-watered posttransplant conditions, MSC increased the mean relative growth rate (RGR) of cucumber and watermelon transplants in the greenhouse. Brushing increased the RGR of watermelon transplants. In 1992, MSC increased the RGR of squash and watermelon transplants grown under posttransplant drought-stressed conditions, while brushing had no effect. Both conditioning treatments controlled plant growth in the greenhouse without diminishing subsequent plant performance.

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Squash leaf curl (SLC) is a virus disease of squash transmitted by the sweetpotato whitefly [Bernisia tabaci (Germ.)]. 'Cucurbita maxima Duch. ex Lam., C. mixta Pang, and C. pepo L. cultivars and the wild taxon. C. texana Gray exhibited severe symptoms in response to SLC in greenhouse and field tests. Symptoms on C. moschata (Duch.) Duch. ex Poir. cultivars were much more severe in greenhouse tests than in field tests. Three wild species, C. ecuadorensis Cutler and Whitaker, C. lundelliana Bailey, and C. martinezii Bailey, were virtually immune in greenhouse tests, but were infected in field tests. Cucurbita foetidissima HBK expressed moderate symptoms in a field test. Benincasa hispida (Thunb.) Cogn., C. ficifolia Bouche, Lagenaria siceraria (Mol.) Standl., Luffa acutangula (L.) Roxb., Luffs aegyptiaca Mill., and Luffs graveolens Roxb. were resistant to SLC in greenhouse and field tests.

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Abstract

This study evaluates light quality and photoperiodic effects on vegetative growth on Cucurbita maxima Duch. In a growth chamber with fluorescent and incandescent lighting the quality of light prior to the dark period, rather than photoperiod, significantly affected internode elongation, and end-of-day red (R) and far-red (FR) treatments demonstrated phytochrome involvement. Internode elongation occurred primarily during the dark period. FR treatments at the beginning of the dark period were most promotive, but FR up to 12 hour into a 16 hour dark period promoted internode elongation significantly. Changes in the ratio of R to FR light at sunset are probably not of sufficient duration and intensity to elicit an end-of-day growth response. In the field, changes in light quality at sunset did not alter the growth habit of the bush or bush-vine phenotypes.

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Abstract

Seedlings of 18 plant types from 5 genera of Cucurbitaceae were analyzed for cucurbitacins, total sugars, and fatty acids and these were correlated with spotted cucumber beetle feeding. The species were: Citrullus colocynthis L. (Schrad.), C. lanatus (Mansf.) Matsumara: Cucumis anguria L., C. dipsaceus Ehrenb., C ficifolius Bouche’C. longipes Hook f., C. melo L., C. myricarpus Naud., C. prophetarum L.: Cucurbita foetidissima H. B. K., C. pepo L.; Lagenaria siceraria (Mol.) Stamdl.; Luffa acutangula (L.) Roxb., and L. cylindrica Roem. Seedling injury ranged from 0 (none) to 3 (severe). Regression analysis indicated that cucurbitacins, total sugars, and the fatty acids (palmitic and linolenic) except linoleic contributed to insect feeding; correlation between concn and feeding was positive. Cucurbitacins, which cucumber beetles were able to locate without feeding, played the major role in seedling susceptibility; next in importance were palmitic acid, linolenic acid, and total sugars. All apparently related to the preference of beetles for specific strains or cultivars. In non-preferred seedlings, preference was induced by topical application of cucurbitacins A, B, C, D, E, and 1 and by the glycosides from C. foetidissimma roots. A barrier seemed to obstruct feeding of the beetles on the upper surface of the cotyledons, even when the attractant cucurbitacins were applied.

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and control of sex expression in melon and cucumber, two other important cucurbits, has been studied in great detail. Briefly, in both melon and cucumber, sex determination is largely controlled by two genes; the A ( andromonoecious ) and G

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reported for the B-class MADS-box duplicated genes of PFGLO1 and PFDEF in Physalis floridana ( Zhang et al., 2015 ). Watermelon is an economically important cucurbit crop widely grown for its large, edible fruit. The watermelon planted area and

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Transplanting generally results in more rapid stand establishment than direct seeding for cucurbit crops. A 2-year field study was conducted to examine the pattern of rooting of watermelon [Citrullus lanatus (Thunb.) Matsum. & Nak.] following usage of different planting methods, and to determine subsequent effects on crop yield. Root length was assessed by obtaining soil cores three times per growing season to a depth of 75 cm. Transplanted watermelons generally had greater root length density in the upper 30 cm of soil 4 to 7 weeks after planting (WAP). However, by 11 to 12 WAP root distribution was similar over the entire 75 cm soil profile for the two planting methods. Total marketable yields were comparable for direct seeded and transplanted watermelons during 1995, but transplanted watermelon yield exceeded direct seeded yield by 40% in 1996. In both years, 90% to 100% of the marketable yield of transplanted watermelons was obtained at the first harvest, compared to 0% to 55% for direct seeded watermelons. These findings suggest that rapid root proliferation of transplanted watermelons may be an important factor in their earlier establishment and increased early yields as compared to direct seeded watermelons.

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Increases in phospholipase D [PLD (EC 3.1.4.4)] and lipoxygenase [LOX (EC 1.13.11.12)] activities are thought to play a critical role in senescence of mesocarp tissues in netted and nonnetted muskmelon (Cucumis melo L.) fruits. We have cloned and characterized two full-length cDNAs, CmPLDα1 and CmLOX1, encoding PLDα and LOX proteins in honeydew melon (C. melo Inodorus Group cv. Honey Brew). Relative levels of expression of the corresponding genes were determined by semi-quantitative RT-PCR in developing and mature fruit mesocarp tissues [20-60 d after pollination (DAP)], as well as in roots, leaves, and stems from 4-week-old and flowers from 6- to 7-week-old plants. The coding regions of CmPLDα1 and CmLOX1 cDNAs are, respectively, 2427 and 2634 nucleotides long, encoding proteins 808 and 877 amino acids in length. CmPLDα1 is very similar to PLDα genes from castor bean (Ricinis communis L.), cowpea (Vigna unguiculata L.), strawberry (Fragaria ×ananassa Duch.) and tomato (Lycopersicon esculentum Mill.) (77% nucleotide identity), and is the first PLD gene cloned from a cucurbit species. CmLOX1 has 94% nucleotide identity to a cucumber (Cucumis sativus L.) LOX gene expressed in roots and 80% identity to cucumber cotyledon lipid body LOX. In general, transcript of CmPLDα1 was much more abundant than that of CmLOX1, but relative levels of transcript in the various organs and tissues were similar for the two genes. Expression was highest in roots, flowers, and fruit mesocarp tissues. CmPLDα1 expression in fruit was essentially constitutive throughout development, although maximum levels occurred at 50 and 55 DAP, respectively, in middle and hypodermal mesocarp. CmLOX1 expression was generally higher in middle than in hypodermal mesocarp with maximum transcript levels occurring at 55 and 50 DAP, respectively. Overall, the patterns of expression of CmPLDα1 and CmLOX1 are consistent with a model in which their encoded enzymes act in tandem to promote or accelerate senescence in fruit mesocarp tissues.

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). In addition, edible seeds of other cucurbits such as melon [ Cucumeropsis mannii and Cucumis melo ( Achigan-dako et al., 2008 ; Loukou et al., 2007 )], squash [ Cucurbita pepo ( Idouraine et al., 1996 )], pumpkin [ C. pepo and Cucurbita

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on the pathogen’s reaction to the NMRILs were found in Minas Gerais (races 20 and 21), Rio de Janeiro (race 19), and Goiás (race18). Minas Gerais and Goiás states are among the major producers of chile pepper and cucurbits in Brazil, and P. capsici

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