Control of muscadine diseases is necessary to minimize yield loss and is especially important for highest quality fresh-market berries. In a systematic disease control spray program, four fungicides registered for grapes were applied sequentially at 10- to 20-day intervals from early bloom until just before harvest to five muscadine cultivars. Objectives of the study were to: 1) determine the effects of the spray schedule on foliage and berry diseases; and 2) study the relationship between disease incidence and resveratrol content of the berries. Resveratrol, a phytoalexin, has shown potential value in prevention and treatment of cardiovascular disease and certain cancer processes. Foliar diseases were rated visually twice during the season. Berry disease ratings were made at harvest. All fungal foliage and berry diseases were significantly reduced by fungicide treatments. Resveratrol was determined separately on berry skins, seed and pulp/juice by gas chromatography/mass spectroscopy (GC/MS). Overall, resveratrol levels in berry skins from unsprayed vines were much higher than those of sprayed vines. Concentrations varied by cultivar and within cultivar by treatment. The relationship between resveratrol concentration in skins and total disease score or scores of specific diseases was not established. Seed resveratrol concentrations differed by cultivar but were not affected by the fungicide treatments. Resveratrol concentration of seed was lower than that of skins. Accumulation of resveratrol in juice/pulp was much lower than in skins and seeds.
J.B. Magee, B.J. Smith, and Agnes Rimando
J.B. Magee, B.J. Smith, and Agnes Rimando
Control of muscadine diseases is necessary to minimize yield loss and is especially important for highest quality if the berries are to be marketed fresh. Throughout the 1998 growing season, vines of five muscadine cultivars (`Noble', `Summit', `Cowart', `Higgins', and `Carlos') were treated under a systematic disease control spray program; four fungicides registered for use on grapes were applied sequentially at 10- to 20-day intervals from early bloom until just before harvest. Control plants received no fungicide. The objectives of the study were to determine the effects of the spray schedule on foliage and berry diseases and to study the relationship between disease incidence and resveratrol content of the berries. Resveratrol is a phytoalexin and has been favorably implicated in cardiovascular disease and certain cancer processes. Foliar diseases were rated visually twice during the season. Berry disease ratings were made at harvest. All fungal foliage and berry diseases were significantly reduced by the fungicide treatments. Resveratrol concentrations were determined separately on berry skins, seed and pulp/juice by GC/MS. Overall, resveratrol levels in berry skins from unsprayed vines were much higher than those of sprayed vines. Concentrations varied by cultivar and within cultivar by treatment. The relationship of skin concentration and total disease score or scores of specific diseases has not been established. Seed resveratrol concentrations differed by cultivar but were not affected by the fungicide treatments. Mean concentration of seed was lower than that of skins. Accumulation of resveratrol in juice/pulp was much lower than in skins and seeds.
R.B. Smith and L.J. Skog
Various cultivars of strawberry (Fragaria ×ananassa Duch.) were stored for 42 h under an atmosphere of 15% CO2 to determine whether their firmness would be enhanced. Compared to initial samples and stored control samples, enhanced firmness was found in 21 of the 25 cultivars evaluated. The CO2 had no effect on color, as measured by Hunter `L', `a' and `b', or on soluble solids concentration (SSC) or pH. There were significant differences among cultivars in firmness; Hunter color `L', `a', and `b'; SSC; and pH.
Theo J. Blom and Richard B. Smith
Summer-grown Hydrangea macrophylla subsp. macrophylla var. macrophylla (Thunb.) were exposed for 1 week to CzH4 at 0,0.5,2.0,5.0,50, or 500 μl·liter-1 in dark storage at 16C for defoliation before cold storage. The number of leaves remaining per shoot for all cultivars decreased with C2H4 concentration, and >5 μl C2H4/liter was effective in defoliating `Kasteln', `Mathilda Gutges', and `Todi' but not `Merritt's Supreme'.
G.J. Galletta, B.J. Smith, and C.L. Gupton
J.P. Syvertsen, M.L. Smith, and B.J. Boman
Effects of salinized irrigation water on tree canopy and root growth, water use, foliar nutrition, and leaching losses below the rootzone were studied during a 2-year period using single tree lysimeters. Eighteen 6-year-old `Valencia' orange trees on either Carrizo citrange (CC) rootstock or sour orange (SO) rootstock were each transplanted into 7.8 m3 drainage lysimeters and irrigated with water having an electrical conductivity of 0.3, 1.6, or 2.5 dS m-1 from a 3:1 ratio of NaCl:CaCl2. Six additional trees (3 on each rootstock) were transplanted into soil without tanks. Trees outside the tanks were smaller, but nutritionally similar to the low salinity trees in lysimeters. Trees on CC were larger, had greater root densities, and were associated with less leaching of ions and nutrients into drainage water from the tanks than trees on SO. High salinity irrigation water reduced canopy growth and ET, but increased fibrous root dry weight. Trees on CC accumulated more Cl in leaves and in fruit juice than those on SO. Leaching loss of total N varied from 2-8% of that annually applied to trees, but up to 70% of the applied N and up to 80% of the applied K were leached from the blank tank with no tree. Salinized trees lost more N and K to drainage water, especially those on SO. Tree size, root density, and irrigation water quality can influence leaching losses beyond the rootzone.
J.B. Magee, B.J. Smith, C.E. Gupton, and J.M. Spiers
The southern highbush (Vaccinium mostly corymbosum) blueberry cultivars Jubilee, Magnolia, and Pearl River, released by the USDA in 1994, were compared with `Premier' and `Climax', two widely planted rabbiteye (V. ashei) cultivars, on the basis of flowering and harvest dates, yield, and physical and chemical quality parameters. The southern highbush cultivars flowered later and ripened at least 1 week before `Climax', one of the earliest rabbiteyes. `Pearl River' berries had less waxy “bloom” and appeared almost black when fully ripe; they had significantly less anthocyanins than the other cultivars compared. `Premier' was lower in titratable acidity and higher in sugars than the southern highbush cultivars. Although data analysis indicated statistical differences in glucose and fructose concentrations among the other four cultivars, these differences were not pronounced. Based on the quality factors used in this study, the southern highbush cultivars compared acceptably to the rabbiteye cultivars.
L.J. Skog, R.B. Smith, and D.P. Murr
`Fantasia' nectarines (Prunus persica L.Batsch) were either stored immediately at 0.5C or subjected to a 48-h delay at 20C in air or with 5% CO2 in air before storage. Samples were evaluated at harvest and after 18, 25, 32, 39 and 46 days storage in air or in 5% O2 with 0%, 4%, 8%, or 12% CO2. All samples were evaluated at optimum ripeness. A combination of delayed storage and elevated CO2 in storage effectively delayed chilling injury (CI) symptoms. Control of CI increased with increasing CO2 level in delayed and nondelayed treatments. Delayed storage was not effective without elevated levels of CO2 in the storage atmosphere. Fruit that was stored without delay did not soften normally during the ripening period and developed a dry, rubbery texture. The effect was enhanced as CI progressed, resulting in increased firmness of ripened fruit with increased storage time. The delayed storage treatments softened normally during ripening, but CI fruit had a dry, mealy texture. Internal conductivity measurements correlated well with CI development. Off-flavors were detected at the higher levels of CO2 storage.
D.A. Smith, J.B. Fitzgerald, and G.E. Meyer
Vitalization is a process whereby senescence is retarded and refrigerated storage can be extended. The process involves hyperhydration of plant materials with selected aqueous solution, thereby flooding interstitial spaces and vascular tissues. Microscopic examination revealed increased size of interstitial spaces and expansion and increased roundness to cells. No disruption of tissues was detected. Turgidity was measured with an Instron Universal Testing Machine equipped with a Kramer Shear Cell. Color was measured with a Minolta color difference meter. Leaves were evaluated for color and turgidity changes during storage. Vitalized leaves did not change significantly in color or turgidity during a 10-week storage period. Untreated leaves lost turgidity and yellowed in storage.
Linda J. Walker, R.B. Rogers, and M.A.L. Smith
In vitro cell cultures of huckleberry and bilberry are sources of phytochemicals for use as food colorants and bioactive chemopreventives. Shoot cultures provide a convenient, presterile source of explants for production of callus rich in extractable pigments or other chemicals. Efficient callus formation only occurs with good-quality shoots. In this study, liquid and gelled support systems were compared in terms of their effect on shoot growth. Gellan gum-based support resulted in excellent shoot proliferation and suitable shoot length for huckleberry cultures, whereas bilberry performed slightly better on agar and agar/gellan gum support. Bilberry had a more-rapid growth rate than huckleberry. Hyperhydricity was found with the use of rafts for both species. These shoot cultures have been used as vegetative explants for callus, and have produced vivid anthocyanins in solution cultures.