¾ mandarin ( Fig. 1 ). ‘Ambersweet’ is the first cultivar designated as a sweet orange, which arose through hybridization rather than as mutations that are near-isogenic to the ancestral sweet orange. ‘Ambersweet’, although classified as a sweet orange for
Jinhe Bai, Elizabeth Baldwin, Jack Hearn, Randy Driggers and Ed Stover
Because of the many concerns about fruit quality and fruit production of `Ambersweet' cultivar, this study was conducted in Florida to evaluate the performance of this cultivar budded on two rootstocks and grown in three locations. The effects of Cleopatra mandarin (CM) rootstock on tree growth, yield, fruit quality, and leaf mineral concentration were compared to those of Swingle citrumelo (SC). Although tree shape differed with the rootstock, no consistent difference was found in tree growth between the two rootstocks. Significant differences in yield, fruit size, and fruit quality were found between the two rootstocks. Fruit produced on CM were large with a rough, thick peel and poor color. Swingle citrumelo rootstock promoted higher yield and better fruit and juice quality than CM. Earlier fruit maturity and higher soluble solids and juice content were obtained from trees grown on the Flatwoods compared to trees grown on the central ridge. With the exception of magnesium, no consistent difference in leaf mineral concentration was found between the two rootstocks.
Jinhe Bai, Elizabeth Baldwin, Jack Hearn, Randy Driggers and Ed Stover
hybrids may be used in standard OJ products. Therefore, to permit unlimited use of a new hybrid in OJ products, the hybrid must be classified as “sweet orange” for the purpose of OJ production. ‘Ambersweet’ is the first hybrid designated as a “sweet orange
W.R. Miller, R.E. McDonald and J. Chaparro
Tolerance of many citrus cultivars to low-dose irradiation treatment is not known. Ten citrus cultivars grown in Florida, including the five orange [Citrus sinensis (L.) Osbeck] cultivars, Ambersweet, Hamlin, Navel, Pineapple, and Valencia, and the five mandarin hybrids (Citrus reticulata Blanco), `Fallglo', `Minneola', `Murcott', `Sunburst', and `Temple', were exposed to irradiation at 0, 0.15, 0.3, and 0.45 kGy, and stored for 14 days at 1 °C or 5 °C plus 3 days at 20 °C, to determine dose tolerance based on fruit injury. Softening of `Valencia', `Minneola', `Murcott', and `Temple' was dose-dependent, but that of other cultivars was unaffected. Only `Ambersweet', `Valencia', `Minneola', and `Murcott' did not develop peel pitting at 0.15 kGy or higher. Total soluble solids of `Ambersweet' and `Sunburst' declined slightly with increasing dose. Titratable acidity (TA) of oranges was not affected, but TA of `Sunburst' and `Temple' juice was slightly reduced by irradiation at 0.45 kGy. Juice flavor of `Hamlin', `Navel', `Valencia', and `Minneola', and pulp flavor of `Hamlin', `Valencia', `Fallglo', `Minneola', and `Murcott' was less acceptable after irradiation at 0.3 or 0.45 kGy. The appearance of all cultivars was negatively affected by the loss of glossiness with the 0.45 kGy dose. Less than 1.0% of fruit decayed and irradiation treatment had no effect on decay. Our study indicates that growers and shippers need to be aware that the effects of irradiation on citrus fruits are highly variable and both cultivar-dependent and dose-dependent.
Charles A. Powell and Robert R. Pelosi
Sixty-eight percent of the `Pineapple', 52% of the `Navel', 46% of the `Valencia', 38% of the `Hamlin', and 0% of the `Ambersweet' orange [Citrus sinensis (L.) Osh.] trees in five Florida citrus nurseries were infected with severe strains of citrus tristeza virus (CTV), as demonstrated by reaction with a monoclinal antibody specific for severe strains of the virus. Severe strains of CTV infected 4%, 46%, 76%, 30%, and 48% of the trees at each of the five nurseries, respectively, indicating a considerable difference in severe strain prevalence among the nurseries. Thirty-five percent of the trees in the scion blocks (budwood source) of the nurseries also contained severe strains of CTV.
Robert D. Hagenmaier and Robert A. Baker
The shrinkage rate of `Marsh' grapefruit (Citrus paradisi Macf.), `Ambersweet' hybrid [(C. reticulata Blanco × C. paradisi Macf. × C. reticulata) × C. sinensis (L.) Osb.] and `Valencia' oranges [C. sinensis (L.) Osb.] was increased 50 % to 150% by washing the fruit with rotary brushes, but was not changed by hand-washing the fruit with cellulose sponges. Internal CO2 increased using both washing methods. Waxed fruit obtained from five Florida packinghouses and cleaned with rotary brushes and waxed had shrinkage rates the same as those of nonwashed controls. Thus, controlling the washing process is important to minimize shrinkage of fresh citrus fruit.
A.K. Alva and T.A. Obreza
Citrus trees planted in alkaline soils typically show iron (Fe) deficiency chlorosis. Currently, Fe-EDDHA (ethylenediiminobis-2-hydroxyphenyl acetic acid) chelate is the most effective source of Fe for high pH soils. Iron humate (FeH), a by-product of the drinking water decolorization process, was compared with Fe-EDDHA for Fe deficiency correction on nonbearing `Ambersweet' orange and `Ruby Red' grapefruit Citrus paradisi Macf., and bearing `Hamlin' orange Citrus sinensis and `Flame' grapefruit trees, all on Swingle citrumelo rootstock, planted on high pH (>7.6) soils. Iron humate was applied under the tree canopy in spring at rates from 2 to 200 g Fe (nonbearing trees), or 22 to 352 g Fe (bearing trees) per tree per year. Application of FeH to nonbearing trees decreased twig dieback rating and increased flush growth, flush color rating, tree size, and leaf Fe concentration. Addition of urea or ammonium nitrate to FeH did not increase Fe availability. Iron amendments (22 g Fe per tree per year) increased fruit yield after the 1st year of application. Further increases in the rate of Fe, from 22 to 352 g Fe per tree per year as FeH, did not significantly increase tree growth, fruit yield, or fruit quality. This study demonstrated that FeH was an effective Fe source for citrus trees planted on alkaline soils.
Walter J. Kender, Ulrich Hartmond and Jacqueline K. Burns
Fruit of 11 citrus cultivars were evaluated for their response to the experimental abscission material metsulfuron-methyl at 2 mg·L-1 (ppm) active ingredient as an aid to mechanical or hand harvest. Cultivars evaluated included `Ambersweet', `Glen Navel', `Hamlin', and `Valencia' oranges [Citrus sinensis (L.) Osb.], `Robinson' tangerine (Clementine × Orlando, C. reticulata Blanco), `Sunburst' tangerine [`Robinson' × `Osceola', C. reticulata × (C. paradisi Macf. × C. reticulata)], `Murcott' and `Temple' tangor (C. reticulata × C. sinensis), `Orlando' tangelo (C. reticulata × C. paradisi), `Ray Ruby', and `Marsh' grapefruit (C. paradisi). Six of the 11 cultivars were effectively loosened by sprays of metsulfuron-methyl (`Hamlin', `Valencia', `Orlando', `Murcott', `Temple', and `Ray Ruby'). Addition of an adjuvant (Kinetic, 0.125%) was necessary for abscission activity in fruit and leaves. Trees sprayed with metsulfuron-methyl in combination with an adjuvant had higher percent cumulative fruit drop, higher internal ethylene, and lower fruit detachment forces (FDF) than trees sprayed with metsulfuron-methyl alone. `Sunburst' tangerine responded poorly to the abscission material in the presence or absence of Kinetic. Leaf loss was greatest in trees sprayed with metsulfuron-methyl and adjuvant, intermediate in trees sprayed with metsulfuron-methyl alone, and least in control trees. Twig dieback was observed in trees of `Valencia' orange and `Marsh' grapefruit sprayed with metsulfuron-methyl. The peel of some cultivars had irregular coloration and developed pitted areas after harvest. Although metsulfuron-methyl is an effective abscission agent for mature citrus fruit, further work is needed to more accurately define conditions for its safe and dependable use.
Anne Plotto, Elizabeth Baldwin, Jinhe Bai, John Manthey, Smita Raithore, Sophie Deterre, Wei Zhao, Cecilia do Nascimento Nunes, Philip A. Stansly and James A. Tansey
profile comparison of USDA sweet-orange-like hybrids vs. ‘Hamlin’ and ‘Ambersweet’ HortScience 49 1262 1267 Baldwin, E.A. Bai, J. Plotto, A. Cameron, R. Luzio, G. Narciso, J. Manthey, J. Widmer, W. Ford, B.L. 2012 Effect of extraction method on quality of
Elizabeth Baldwin, Jinhe Bai, Anne Plotto, John Manthey, Smita Raithore, Sophie Deterre, Wei Zhao, Cecilia do Nascimento Nunes, Philip A. Stansly and James A. Tansey
comparison of USDA sweet-orange-like hybrids vs. ‘Hamlin’ and ‘Ambersweet’ HortScience 49 1262 1267 Baldwin, E. Plotto, A. Manthey, J. McCollum, G. Bai, J. Irey, M. Cameron, R. Luzio, G. 2010 Effect of liberibacter infection (huanglongbing disease) of citrus