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Esmaeil Fallahi, Zahra Mousavi, and D. Ross Rodney

The influence, of 10 rootstocks on growth, yield, and fruit quality of `Orlando' tangelo (Citrus paradisi Macf. × C. reticulata Blanco) was studied for 7 years under the arid climate of southwestern Arizona. Trees on macrophylla (Alemow) (C. macrophylla Wester) were the most precocious and produced the highest yields 4 years after planting. Seven-year cumulative yields of trees on Carrizo citrange [C. sinensis (L.) Osbeck × Poncirus trifoliata (L.) Raf.], Yuma citrange (P. trifoliata × C. sinensis), Volkamer lemon (C. limon Burm f.), rough lemon (C. jambhiri Lush), Taiwanica (C. taiwanica), and macrophylla were similar and higher than those on Savage citrange (P. trifofiata × C. sinensis), Batangas mandarin (C. reticulata Blanco), Ichang pummelo (C. ichangensis hyb.), and Palestine sweet lime (C. limettoides Tan.). Trees on Carrizo citrange had relatively large tree canopies and larger fruit, and fruit from trees on Volkamer lemon and rough lemon was lower in total soluble solids concentration (TSS) and total acids (TA) than fruit from trees on other rootstocks. Fruit from trees on Savage citrange was smallest but had the highest TSS. Considering yield, growth, and/or various quality factors, Volkamer lemon, rough lemon, Yuma citrange, and particularly Carrizo citrange, are suitable for `Orlando' tangelo in the arid regions of the southwestern United States. Trees on macrophylla, Savage citrange, and Ichang pummelo had small canopies and were least productive. `Orlando' tangelo trees on Savage citrange and Ichang pummelo rootstocks, however, might be good choices at a spacing closer than 7 × 7 m because of their high fruit TSS and fruit size, respectively. Trees on Palestine sweet lime declined and had low yields, and those on Batangas mandarin had low yields and poor fruit quality. These rootstocks are not recommended for `Orlando' tangelo under conditions similar to those of this experiment.

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James Ferguson, Michael Ziegler, and Jack Hebb

Soil incorporation of poultry litter can damage roots of citrus trees grown on shallow soils in southern Florida. Using an alternative application method, young `Minneola' tangelo trees (Citrus reticulata Blanco × C. paradisi Macf.) on Cleopatra mandarin rootstock (C. reticulata Blanco) on bedded groves in southeast Florida were fertilized for 18 months after planting with surface-banded poultry litter (PL) overlaid with wood chips (WC). PL/WC was applied at 142, 284, and 425 kg·ha-1 N in two applications/year in one 0.6-m band within the dripline of trees planted at 278 trees/ha. Other treatments with different N rates included 220 kg·ha-1 N broadcast in the middle of the bed twice a year and 116 kg·ha-1 N as controlled release fertilizer applied within the dripline of trees in three applications per year. Eighteen months after planting, growth of trees receiving PL/WC treatments of 142, 284, and 425 kg·ha-1 N per year and 116 kg·ha-1 N per year was similar and greater than growth of trees receiving PL broadcast in grove middles at 220 kg·ha-1 N per year. Soil P, Ca, and Mg levels beneath the three banded PL/WC treatments were higher than in other treatments; in all treatments leaf N levels were optimum, but leaf P, K, Ca, Mg, and Fe levels were excessive. Banded PL/WC treatments applied at 142 kg·ha-1 N per year and even lower rates may be adequate for growth of young citrus trees, especially in terms of reducing excessive soil and leaf nutrient levels.

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Paula Morales, Frederick S. Davies, and Ramon C. Littell

Pruning and skirting (removal of low-hanging limbs) effects on canopy temperature, relative humidity (RH), and fruit yield and quality of `Orlando' tangelo trees (Citrus paradisi Macf. × Citrus reticulata Blanco) on `Carrizo' citrange rootstock [Poncirus trifoliata (L.) Raf. × Citrus sinensis (L.) Osb.] were studied at the Univ. of Florida Fifield Farm in Gainesville, Fla., in 1996–97. In the first season, treatments consisted of skirted and non-skirted trees. In the second season, two skirting (skirted and non-skirted) and three pruning (gable-top, flat-top, and non-pruned) treatments were evaluated. Neither RH nor air temperature was affected in the lower canopy by any treatment. However, temperature in the upper canopy of flat-topped trees was higher than that in gable-topped or non-pruned trees, and reached >45 °C during spring and summer. Fruit number and yield were decreased by pruning and skirting in one season. Skirted, gable-topped trees had the lowest yields, followed by skirted, flat-topped and non-skirted, gable-topped trees. All other treatments produced yields similar to those of non-skirted, non-pruned trees. Pruning increased the percentage of large fruit and reduced the percentage of small fruit. Skirting and pruning had no effect on blemish incidence with the exception of wind scar, which was higher in skirted than in non-skirted trees in the first season. During both seasons the main causes of packout reduction were rust mite and wind scar damage. Regardless of treatment, rust mite damage was much higher in the lower than in the upper canopy because of lower average temperatures and higher RH. Pruning effects on fruit quality were similar to those reported previously, but skirting had no effect on most fruit quality factors.

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Alan W. Meerow and Tomás Ayala-Silva

guarume ‘Miami Sunrise’, ‘Miami Sunset’, and ‘Tangelo’ are seedling selections from progeny grown from seed received in 2000. We believe that these fast-growing cultivars have great potential for use as landscape shrubs in USDA Hardiness Zones 9A–11

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Steven Pao, Peter D. Petracek, and G. Eldon Brown

Peeling and storage characteristics of citrus fruit infused with water or enzyme solution were compared. Fruit were vacuum- or pressure-infused with water or water-containing pectinase. The enzyme treatment did not affect peeling times of white or red grapefruit, oranges, or tangelos. Pressure and vacuum infusion methods produced similar results. Grapefruit and oranges infused with water had significantly less juice leakage and were firmer than fruit infused with enzyme. Microbial levels and respiration rates and ethylene emanation during storage were the same for enzyme- and water-treated fruit.

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Frederick G. Gmitter Jr. and Xubai Ling

A method was developed to produce nonchimeric, autotetraploid Citrus plants via in vitro somatic embryogenesis in the presence of colchicine. Undeveloped ovules from immature fruit of `Valencia' sweet orange (Citrus sinensis [L.] Osb.) and `Orlando' and `Minneola' tangelos (Citrus reticulata Blanco × Citrus × paradisi Macf.) were held on Murashige and Tucker medium with 500 mg malt extract/liter and 0.0090, 0.01%, or 0.10% colchicine for 21 days. Embryogenesis from tangelo ovules was suppressed by 0.10% colchicine, but no such effect was observed among sweet orange ovules. Colchicine treatments had no subsequent effect on embryo germination. The numbers of chromosomes in root tip cells showed that both tetraploid and diploid `Valencia' and `Orlando' plants were recovered from colchicine treatments. `Minneola' cultures produced only diploid plants. Tetraploid plant morphology was typical for Citrus tetraploids. Examination of chromosome numbers in root tip, shoot, and leaf meristems indicated that the regenerants were nonchimeric. Such nonchimeric tetraploids will be useful parents for interploid hybridization directed toward development of seedless triploid Citrus scion cultivars.

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Lawrence R. Parsons, T. Adair Wheaton, and William S. Castle

Conversion of wastewater to reclaimed water for crop irrigation conserves water and is an effective way to handle a growing urban problem: the disposal of wastewater. Water Conserv II is a large reclaimed water project developed by Orlando and Orange County, Fla., that presently irrigates ≈1900 ha of citrus. The project includes a research component to evaluate the response of citrus to irrigation using reclaimed water. Citrus trees in an experimental planting responded well to very high application rates of reclaimed water. Irrigation treatments included annual applications of 400 mm of well water, and 400, 1250, and 2500 mm of reclaimed water. The 2500-mm rate is excessive, and since disposal was of interest, this rate was used to determine if citrus could tolerate such high rates of irrigation. The effects of these treatments were compared on `Hamlin' orange [Citrus sinensis (L.) Osb.] and `Orlando' tangelo (C. paradisi Macf. × C. reticulata Blanco) combined with four rootstocks: Carrizo citrange [Citrus sinensis (L.) Osb. × Poncirus trifoliata (L.) Raf.], Cleopatra mandarin (C. reticulata Blanco), sour orange (C. aurantium L.), and Swingle citrumelo (C. paradisi × P. trifoliata). Growth and fruit production were greatest at the highest irrigation rate. Concentration of soluble solids in the juice was usually lowered by the highest irrigation rate, but total soluble solids per hectare were 15.5% higher compared to the 400-mm rate, due to the greater fruit production. While fruit soluble solids were usually lowered by higher irrigation, the reduction in fruit soluble solids observed on three of the rootstocks did not occur in trees on Carrizo citrange. Fruit peel color score was lower but juice color score was higher at the highest irrigation rate. Crop efficiency (fruit production per unit of canopy volume) was usually lower at the 2500-mm rate and declined as trees grew older. Weed cover increased with increasing irrigation rate, but was controllable. Irrigation with high rates of reclaimed water provided a satisfactory disposal method for treated effluent, benefited growth and production of citrus, and eliminated the need for other sources of irrigation water. Reclaimed water, once believed to be a disposal problem in Florida, is now considered to be one way to meet irrigation demands.

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Jacqueline K. Burns

Oxygen uptake and glycosidase activities were examined in normal and granulated juice vesicles of several citrus fruit. Oxygen uptake was low in normal juice vesicles isolated from freshly harvested `Lee' tangelos [Citrus reticulate Blanco cv. Clementine × (Citrus paradisi Macf. cv. Duncan × Citrus reticulate Blanco cv. Dancy)] and stored `Dancy' tangerine (C. reticulate Blanco) and `Marsh' grapefruit (Citrus paradisi Macf.) (35.7, 17.9, and 11.6 μl O2/hr per g fresh weight, respectively), but was 2- to 3-fold higher in granulated juice vesicles. As severity of granulation increased in grape. fruit, O2 uptake increased. Oxygen uptake in normal and disordered juice vesicles of all citrus fruit examined was reduced to nondetectable levels with 0.1 mM KCN and was insensitive to salicylhydroxamic acid. α - and β -galactosidase and α- and β -glucosidase activities were present in extracts of normal grapefruit juice vesicles (123, 214, 51, and 25 nmol·hr-1·g-1 fresh weight, respectively) and was 2- to 3-fold higher in extracts of granulated tissue. α- and β -mannosidase activities, nondetectable in normal juice vesicle extracts, were present in extracts from granulated tissue. The results suggest that increased metabolic activity occurs in granulated juice vesicles and the energy produced may be used to support cell wall synthesis and modification. Increases in O2 uptake and glycosidase activities correlate well with observed symptoms of section-drying in citrus.

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Tyler Simons, Hanne Sivertsen, and Jean-Xavier Guinard

tangelo (500+ pieces each) were obtained from a local wholesale grocery store and produce wholesalers. The fruit obtained came from the same pallet with all boxes bearing the same run number to ensure consistency. The fruit consisted of specified varieties

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Ed Stover and Greg McCollum

susceptible category and grapefruit showed slightly lower susceptibility. “Other citrus” grown in Florida is mostly mandarin hybrids (tangors, tangerines, and tangelos), which represent ≈9300 ha or 4% of all Florida citrus ( NASS, 2008 ). Tangors are natural