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Control of downy (Pseudoperonospora cubensis) and powdery [(Podosphoera xanthii (Sphaerotheca fuliginea)] mildew on `Sweet Dumpling' winter squash (Cucurbita maxima) was evaluated at the University of Florida, IFAS, Indian River Research and Education Center (IRREC), in Fort Pierce, Florida during the Spring of 2005. Three foliar spray fungicide treatments were evaluated against an untreated control. Powdery and downy mildew ratings (estimated percentage of foliage damage) and marketable yields (mt/ha) were measured. Plants in the untreated plots had significantly higher powdery and downy mildew ratings. All fungicide treatments significantly reduced both mildews. There were no significant differences among treatments for marketable yield. Although the level of disease occurrence was not sufficient to reduce yields, Gavel alternated with Nova, Bravo Ultrex weekly, and Cabrio + Forum alternated with Bravo Ultrex + Manzate 75WG reduced downy mildew by ≥50%.

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Plant regeneration from tissue cultures of summer squash (Cucurbita pepo L. ev. YC60) has been observed. Embryogenic callus tissues were initiated when cotyledons of mature seeds were excised and cultured on Murashige and Skoog (MS) medium supplemented with either 22.7 μm 2,4-D or a combination of 4.7 μm 2,4,5-T, 4 μm BA, and 0.5 μm kinetin. Clusters of somatic embryos were found in callus tissue. Maturation of these somatic embryos was effected by transfer of embryogenic callus tissues to MS supplemented with 0.5 μm NAA and 0.25 μm kinetin. Regenerated mature plants were morphologically normal and set fruits containing seeds that germinated normally. Chemical names used: 6-benzylaminopurine (BA); 2,4-dichlorophenoxyacetic acid (2,4-D); α - napthaleneacetic acid (NAA); 2,4,5-trichlorophenoxyacetic acid (2,4,5-T).

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Control of downy (Pseudoperonospora cubensis) and powdery mildew [(Podosphoera xanthii (Sphaerotheca fuliginea)] on `Sweet Dumpling' winter squash (Cucurbita maxima) was evaluated at the University of Florida, IFAS, Indian River Research and Education Center (IRREC) in Fort Pierce, Florida during Spring 2004. Seven foliar spray fungicide treatments were evaluated against an untreated control. Powdery and downy mildew ratings (estimated percentage of foliage damage) and marketable yields (mt/ha) were measured. Plants in the untreated plots had significantly higher powdery and downy mildew ratings. All fungicide treatments reduced powdery mildew on adaxial leaf surfaces. Downy mildew appeared unusually late in the crop season and all fungicide treatments significantly reduced it. There were no significant differences among treatments for marketable yield. Although the level of disease occurrence was not sufficient to reduce yields, each foliar spray treatment significantly reduced powdery and downy mildew.

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Mature zucchini squash plants (Cucurbita pepo L.) were grown under four NO3:NH4 ratios (1:0, 3:1, 1:1, and 1:3) to determine effects on macronutrient nutrition. Plants were grown in solution culture under greenhouse conditions. Treatments were applied at first bloom. Highest uptake of Ca and Mg occurred in the 1:0 NO3:NH4 treatment while higher K uptake was found in the 3:1 NO3:NH4 treatment. Total nitrogen uptake was greatest in the 1:1 and 3:1 NO3:NH4 treatments. A 3:1 NO3:NH4 ratio applied at first bloom gave best overall uptake of N, K, Ca, and Mg.

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Mature zucchini squash plants (Cucurbita pepo L.) were grown under four NO3:NH4 ratios (1:0, 3:1, 1:1, and 1:3) to determine effects on macronutrient nutrition. Plants were grown in solution culture under greenhouse conditions. Treatments were applied at first bloom. Highest uptake of Ca and Mg occurred in the 1:0 NO3:NH4 treatment while higher K uptake was found in the 3:1 NO3:NH4 treatment. Total nitrogen uptake was greatest in the 1:1 and 3:1 NO3:NH4 treatments. A 3:1 NO3:NH4 ratio applied at first bloom gave best overall uptake of N, K, Ca, and Mg.

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The Gray Zucchini cultivar of summer squash is widely consumed as a fresh market vegetable in Northwest Mexico but is highly suceptible to viral diseases. Gray Zucchini type lines were developed by interspecific hybridization using a local landrace of Cucurbita moschata, which has shown high levels of viral resistance, as male parent and suceptible C. pepo cv. classic as female. The lines were obtained after 4 backcrossing and 3-5 selfing generations. In 1993 average commercial yield of first generation hybrids between lines was 28,155 kg/ha followed by line × Gray Zucchini hybrids, lines, commercial hybrids (Classic. Corsair, Onyx, Raven), and open pollinated cultivars (Gray Zucchini, Black Zucchini) with 26,594, 21,062, 18,862 and 10,172 kg/ha respectively. Yield was inversely related to symptoms of viral infection.

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Roots of acorn squash were washed from soil cores, dried and weighed. The cores were taken in a pattern about individual plants to reflect the roots present in each selected zone at different periods during the season. A different plant was sampled at each period so that there would be no effect from previous sampling. The root weights were multiplied by factors commensurate with the volume of soil represented by each core sample. Two years data have indicated that irrigation level effects the size of the root system but not its distribution. Density of roots was always greatest in the top 15 cm of soil and this zone of the greatest density progressively moved out from the center of the plant with time. Pattern of root distribution was not effected by plastic mulch, bare ground, trickle or furrow irrigation treatments. Root distribution was the same on all sides of the plant.

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Abstract

In a replicated field test in 1982 where natural virus incidence was 25% watermelon mosaic virus 1 (WMV-1) and 75% WMV-2, we observed mosaic symptoms at harvest in leaves and fruit of the yellow-fruited Cucurbita pepo L. ‘Butterbar’, ‘Early Prolific Straightneck’, and ‘Multipik’. The range in percentage of diseased plants among the cultivars was small (26–33%), but total diseased fruit exceeded 40% in ‘Butterbar’ and ‘Early Prolific Straightneck’ and was less than 10% in ‘Multipik’. In a replicated field test in 1983, ‘Early Prolific Straightneck’ and ‘Multipik’ squash plants mechanically inoculated at early flowering with WMV-1, WMV-2, and zucchini yellow mosaic virus (ZYMV) became 97–100% foliar diseased. Production of diseased fruit was significantly greater in virus inoculated ‘Early Prolific Straightneck’ plants (all 3 viruses) than in uninoculated plants, and significantly greater in ‘Multipik’ plants inoculated with ZYMV or WMV-1 than in those inoculated with WMV-2 or not inoculated. In both tests, there were significant delays in the development of fruit symptoms in virus infected ‘Multipik’ when virus infection was mainly WMV-2. The evidence suggests fruit symptoms were caused by viruses other than WMV-2, and that WMV-2 does not induce symptoms in fruit of ‘Multipik’.

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Grafting of watermelon scions onto squash or pumpkin (Cucurbita), bottle gourd (Lagenaria), wax gourd (Benincasa), or watermelon (Citrullus) rootstocks is practiced in most of the major watermelon production regions of the world. Advantages of grafting are protection against soilborne diseases, resistance to nematodes, and overall increased vigor of plants resulting in higher yield and better fruit quality. Disadvantages include increased cost of seedling production and the potential of altered horticultural characteristics of cultivars used as scions. With problems associated with watermelon vine decline in recent years in Florida and the increasing cost of soil fumigants, the use of grafted watermelon seedlings should be explored. Four grafting techniques for watermelon are common: splice, side insertion, approach, and hole insertion. The approach graft, though labor intensive, doesn't require exacting control of temperature and humidity after making grafts and may be well suited to south Florida conditions. All other grafts require excellent control of the post-grafting environment and a careful transition from low light and high humidity to high light and low humidity. A preliminary evaluation of grafted and ungrafted plants during Fall 2005 compared `Tri-X 313', `Palomar', `Precious Petite', and `Petite Perfection' on several rootstocks. Most rootstock/scion combinations produced fruit of normal size, appearance (internal and external), and soluble solids content. Some combinations resulted in irregular, pumpkin-shaped fruit and slightly higher incidences of hollowheart.

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Butternut squash was harvested at two stages of maturity in 1994 and was cured for 10 days at 26°C and 80% or 95% relative humidity (RH) before storage in air at 12°C and 65% or 80% RH for 144 days. Fresh weight was assessed right after harvest along with carotene (milligram per 100 grams fresh weight), carbohydrates (milligrams per gram dry weight) and internal color (L, a, b). Percent weight loss and all quality components were assessed immediately after curing and every 48 days thereafter. Weight loss increased with days in storage and was substantially minimized by a humidified environment down to 6%. The 95% curing treatment reduced weight loss to levels below the upper threshold for consumer acceptance (<15%) after 144 days. Maturity at harvest did not affect weight loss during storage, but rather the percent dry weight. Beta-carotene increased by >100% during storage. A positive correlation was established between weight loss and beta-carotene and also between the a value and beta-carotene. Curing at 95% RH obviously reduced beta-carotene content to less than one-third of its corresponding amount in noncured fruit. Sucrose increased as glucose and fructose and starch decreased during storage in cured and noncured fruit. Starch was found to decrease by 26% after 144 days in storage. The lowest levels of starch were found early during storage in fruit cured at 95% RH, but the difference between treatments disappeared by the end of storage.

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