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Four high-yielding sweetpotato [Ipomoea batatas (L.) Lam.] cultivars displayed substantial leaf shedding, under typical field production conditions, that was not due to pathological or herbivory causes. Losses ranged from ≈ 45% to 60% of the total leaves formed by the normal harvest date during 2 years. There was a strong positive correlation between leaf shedding and the number of vines (r2 = 0.80) and nodes (r2 = 0.89) per plant. Likewise, positive correlations were found between leaf shedding and total dry weight (r2 = 0.67), root fresh weight (r2 = 0.65), root dry weight (r2 = 0.60), and vine dry weight (r2 = 0.68). Distinct differences were found among cultivars in dry-matter allocation within the plant. `Jewel' allocated a lower percentage of dry matter into vines and a higher percentage into storage roots. Estimated leaf dry matter losses due to leaf shedding ranged from 1.2 to 2.6 t·ha-1. High leaf losses appear to be closely related to vigorous vine growth and subsequent shading of older leaves but did not have a negative impact on storage root yield in the cultivars tested.

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Authors: and

Under typical field production conditions, four high-yielding sweetpotato cultivars (Centennial, Jewel, Regal and Resisto) were found to lose substantial amounts of leaves due to natural senescense rather than pathological or herbivory causes. Leaf loss by the normal harvest date ranged from 46 to 63% of the total leaves formed in 1991 and 48 to 59% in 1992. There was a strong positive correlation between leaves lost and the number of vines (r2 = 0.80) and nodes (r2 = 0.89) per plant. Positive correlations were also found between leaf loss and total dry weight of the plant (r2 = 0.67). root fresh weight (r2 = 0.65). root dry weight (r2 = 0.60), and vine dry weight (r2 = 0.68). Distinct differences were found among cultivars in dry matter allocation within the plant. Of the cultivars tested, 'Jewel' allotted a lower percentage of dry matter into vines and a greater percentage into storage roots. Estimated leaf dry matter losses due to leaf shedding ranged from 1.2 to 2.6 MT·ha-1. Amount of leaf loss appeared to be closely related to vigorous vine growth and subsequent shading of older leaves, though leaf loss did not have a negative impact on storage root yield in the cultivars tested.

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Latex is known to act as a natural defense system in some laticiferous plants against certain herbivores. The importance of latex produced by the sweetpotato, Ipomoea batatas, Lam., as a defense mechanism against the sweetpotato weevil, Cylas formicarius elegantulus (Summers) (Coleoptera: Curculionidae), was tested. Distinct genetic and environmental differences were found in latex production in a broad cross-section of sweetpotato germplasm (96 lines). Most lines produced 2.6 to 10 mg fwt-vine-1 of latex when the second internode from the apex was severed. Some lines, however, produced substantially more, the highest being 48.3 mg·vine-1. The percent dwt of the latex exudate ranged from 2.5 to 54, with most lines falling within the 10 to 22.5% range. The amount of latex (fwt) released varied (1.9X) with differing environmental conditions (primarily light intensity). Young vine material produced more latex and had less feeding by the weevil than in older more mature portions of the vine. Application of latex to the surface of root cores markedly reduced feeding (67%) and oviposition (92%) after 24 hours in choice and oviposition in no choice experiments. Addition of latex to a semi-artificial media also significantly reduced feeding. Leaf feeding location (veins) and direction (basipetal), however, were not indicative of a deterrent role for latex. Collectively, existing evidence does not support a significant deterrent role for latex with regard to the sweetpotato weevil, however, additional information is needed on latex chemistry and quantitative and qualitative variation in latex within the sweetpotato genepool.

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Authors: and

Abstract

Mechanically harvested southernpeas (Vigna unguiculata (L.) Walp cv. Purple Hull Pink Eye lost substantial green color within 2 – 3 hours after harvest. Color loss was greater at higher temperature. Color changes were more closely related to O2, CO2, acetaldehyde and ethanol concentration in the load atmosphere than to endogenous ethylene concentrations. Solids and total sugar content decreased after harvest and were not affected by product temperature within the range studied. Flavor and off-flavor acceptability ratings were closely related to time from harvest, product temperature and load atmosphere O2 and CO2 concentrations, but were not closely associated with ethylene, acetaldehyde or ethanol concentrations.

Open Access

Abstract

Postharvest life of cut Ranunculus asiaticus flowers was substantially extended with low temperature storage; 0° and 5°C were superior to higher temperatures. Extended storage duration, however, increased the rate at which floral senescence occurred upon removal from cold storage.

Open Access
Authors: and

Abstract

Repression of specific growth parameters of Tetragonia tetragonioides (Pall.) Kuntze (syn. Tetragonia expansa Murray) was studied after application of two types of growth regulators. Succinic acid-2,2-dimethylhydrazide (SADH) decreased stem height and dry weight progressively with increased concentration. Ratio of leaf dry weight to stem dry weight increased with concentration. Maleic hydrazide (MH) caused substantial reduction of fruit weight, with fruit number decreasing only at higher concentrations. Whole plant fresh weight and leaf area decreased only with a multiple 500 ppm application of MH. Leaf to fruit fresh weight ratio increased with concentration and number of applications. A formulation C6 to C12 fatty alcohols (Off-Shoot T) had little effect on fruit development and leaf area.

Open Access

Abstract

Five sweet potato [Ipomoea batatas (L.) Lam] cultivars with diverse flavor characteristics were evaluated by a consumer panel for intensity of taste and aftertaste and for acceptance using a Food Action Rating Scale (FACT). ‘Jewel’ (United States) and ‘Tainung-57’ (The People’s Republic of China) had a moderately intense flavor and received the highest acceptance rating, whereas ‘Morado’ (Central America) and ‘Sumor’ and ‘HiDry’ (new USDA releases) had the lowest intensity of taste and acceptance scores. Correlation coefficients between acceptance scores and taste intensity were not significant for all cultivars, indicating that consumer acceptance of sweet potatoes of diverse flavor characteristics may be based on other sensory attributes. Further investigations using trained profile panels and simultaneous analyses of taste/aroma constituents could determine criteria for consumer acceptance of sweet potato.

Open Access

Abstract

Pepper (Capsicum frutescens L. cv. Hot Hungarian Yellow Wax) and polebeans (Phaseolus vulgaris L. cv. Dade) were grown in an intensive production system with film mulch, broad-spectrum soil fumigation and trickle irrigation. Nitrogen was applied through the trickle irrigation tubes at 0.56, 1.12, 2.24, and 4.48 kg/ha per day for the pepper and 0.56, 1.12, 2.24, and 3.36 kg/ha per day (doubled 6 weeks after seeding) for polebeans. Potassium was applied at 0.83 times the N rate. The N and K were applied twice weekly for the polebean and with every irrigation for the pepper. Marketable pepper yields ranged from 59.6 MT/ha with the low fertilizer rate to 96.0 MT/ha with high fertility. Yield increases with increasing fertilizer rates were not as great with polebeans as with peppers but there was a trend for higher yields with increasing fertilizer rates.

Open Access

Abstract

‘Redhaven’ peach (Prunus persica (L.) Batsch) that were in rest were exposed for 96 hours to 2.5, 5, 10.5, or 21% O2. A second group was exposed to 2.5% O2 for 1, 2, 4, or 6 days. Bud break was enhanced only by 2.5 or 5% O2. Rest release was also influenced by the duration of exposure to low O2. Plants exposed for 2, 4, or 6 days to 2.5% O2 showed faster bud break than did those exposed to the same concentration for 0 or 1 day.

Open Access

Abstract

Pepper (Capsicum frutescens L.) and summer squash (Cucurbita pepo var. melopepo (L.) Alef.) were grown in immediate succession in undisturbed beds using trickle irrigation with various treatments. Highest combined yield in metric tons/ha for both crops was obtained with film mulch + soil fumigation (117.6) followed by film mulch (112.3), soil fumigation (93.4) and control (69.0), respectively. Yield from the second crop was negatively correlated (r=−.87) with the degree of plant infection with root-knot nematode (Meloidogyne incognita (Kofoid & White) Chitwood). Intensive production in this manner allows fixed costs to be defrayed over two crops thus increasing the magnitude of return per dollar invested. Multiple cropping of pepper and squash with trickle irrigation has an excellent potential in south Georgia provided nematodes and other soil-borne pathogens can be adequately controlled.

Open Access