Star Ruby Research Articles

Alternaria Brown Spot of Minneola in Greece; Evaluation of Citrus Species Susceptibility

During the last three years, a new disease was observed in northwestern Greece on Minneola trees, hybrid of mandarin and grapefruit. On May small brown necrotic leaf spots surrounded by yellow halo areas of various sizes appeared and covered a major portion of the leaves with extension of necrosis into the veins. On young fruits small, slightly depressed black spots were the first symptoms, which later became 2–7 mm in diameter. Brown spots were observed on the leaves and fruits in several orchards in the same area, causing leaves and fruits to drop. In some orchards over 50% of the fruits were affected. From the fruit and leaf spots the typical small-spore species Alternaria alternata was isolated. Pathogenicity tests were performed by artificially inoculating fruits of Minneola, common mandarin and Clementine. The symptoms of the disease were reproduced only on fruits of Minneola hybrids by the specific strain of the fungus Alternaria alternata pv. citri. Different citrus susceptibility tests indicated that mandarins Minneola, Nova and Page were very susceptible to tested isolates while Clementine SRA and Poros Clementine were not. All lemons and lime Seedless were not susceptible. Grapefruit New Hall was not susceptible, while the Star Ruby was. Orange Lane Late, Navel Late, Oval Poros, Olinda, Navel Athos were not susceptible and only Moro showed reaction being slightly susceptible only to one isolate.

Presence of diverse ratios of lycopene/β-carotene in five pink or red-fleshed citrus cultivars

Pink or red-fleshed fruit mutations are commonly found in grapefruit, sweet orange, and occasionally in lemon, which combine novel appearance with fine eating quality. In order to identify the major coloured pigments, high performance liquid chromatography (HPLC) with ultraviolet detection was applied for the separation and characterization of carotenoids from five pink or red-fleshed citrus cultivars. As a result, both lycopene and β-carotene with similar HPLC profiles were detected in the five citrus cultivars, ‘Fengdu’ red-fleshed pomelo ( Citrus grandis (L.) Osbeck), ‘Guanxi’ sweet pomelo red mutant, ‘Hirado Buntan’ pomelo, ‘Cara Cara Navel’ orange ( C. sinensis (L.) Osbeck) and ‘Star Ruby’ grapefruit ( C. paradisi Macf.). ‘Star Ruby’ contained the highest lycopene and β-carotene content in its flesh. However, although the significant correlation between the concentrations of lycopene and β-carotene was detected with a coefficient of 0.9692 ( P < 0.01), ratios of lycopene/β-carotene were different among the cultivars. Post-harvest biosynthesis verified that the flesh itself synthesized carotenoids rather than acquiring them via transport from other tissues. In addition, a product feedback regulation mechanism might be involved in the process of carotenoid biosynthesis.

Characterization of blond and Star Ruby (red) Jaffa grapefruits using antioxidant and electrophoretic methods

SummaryAntioxidant and electrophoretic methods were used to characterize the quality differences between blond and Star Ruby (red) grapefruits. Dietary fibre, minerals and trace elements, total polyphenols, anthocyanins, flavonoids, phenolic and ascorbic acids were also determined. The antioxidant potential of red grapefruit was significantly higher than that of the blond fruit (P &lt; 0.05) and correlated well with the total polyphenols (R2 from 0.8456 to 0.9711). In both the cultivars studied, thirty‐two electrophoretic bands were detected [sodium dodecyl‐polyacrylamide gel eletrophoresis (SDS‐PAGE)]. The main electrophoretic bands occurred between 20 and 43 kDa in both grapefruits with few minor differences between the varieties. Our findings indicate the following (i) red grapefruit is preferable: it has a higher concentration of bioactive compounds and antioxidant potential than the blond; (ii) 1, 1‐diphenyl‐2‐picrylhydrazyl (DPPH) test is a more sensitive method for the determination of antioxidant potential; (iii) there are some minor differences in electrophoretic patterns; (iv) antioxidant and electrophoretic methods are a good combination for characterization of differences of the same citrus fruits.

Physiological responses of ‘Murcott’ mandarins and ‘Star Ruby’ grapefruit to anaerobic stress conditions and their relation to fruit taste, quality and emission of off-flavor volatiles

During their postharvest handling citrus fruit may be exposed to various anaerobic stresses, which may occur, for example: during quarantine treatments, because of inadequate ventilation in containers and storage rooms, following application of waxes that restrict gas exchange through the peel and after packing the fruit in plastic liners. It is known that mandarins tend to develop off-flavors much more rapidly than other citrus varieties, for reasons that are not yet understood. In this study, we evaluated the physiological responses of ‘Murcott’ mandarins and ‘Star Ruby’ grapefruit to anaerobic stresses by exposing them to N 2 atmospheres for 6, 12, 24, 48 or 72 h at 20 °C. It was found that mandarins held in N 2 showed earlier and higher increases in respiration rate than grapefruit, with consequently earlier increases in CO 2 levels in their internal atmospheres. Furthermore, mandarins held in N 2 exhibited higher and earlier increases than grapefruit, in the accumulation of the off-flavor volatiles, ethanol and acetaldehyde in the juice. Unlike grapefruit, mandarins responded to the anaerobic treatment by increasing the production of the stress hormone ethylene. Finally, sensory evaluations indicated that the taste of mandarins markedly deteriorated following exposure to anaerobic conditions and was rated as unacceptable after 48 h in N 2, whereas the taste of grapefruit deteriorated only slightly and was rated acceptable even after 72 h of exposure to N 2. Overall, the data presented herein demonstrate that ‘Murcott’ mandarins are much more sensitive to exposure to anaerobic stresses than ‘Star Ruby’ grapefruit, and that this high sensitivity may be partly responsible for the much more rapid decline in their marketability and eating quality after harvest.

Citrus paradisi and Citrus sinensis flavonoids: Their influence in the defence mechanism against Penicillium digitatum

Citrus peel is rich in flavanone glycosides and polymethoxyflavones. In view of their importance for industrial application as well as for their pharmacological properties, their content was analyzed in the mature fruits of several Citrus paradisi (grapefruit) and Citrus sinensis (orange) varieties, with a view to select the most interesting for isolation. The results shows that the Star Ruby grapefruit and the Sanguinelli orange stand out for their high contents of naringin and hesperidin, respectively. The presence of the polymethoxyflavones nobiletin, heptamethoxyflavone and tangeretin, could be ascertained in all the grapefruit varieties analysed. Higher polymethoxyflavone levels were recorded in orange, with Valencia Late showing the greatest nobiletin, sinensetin and tangeretin contents and Navelate the highest heptamethoxyflavone levels. An in vitro study revealed that these compounds acted as antifungal agents against Penicillium digitatum, the polymethoxyflavones being more active than the flavanones in this respect. The possible participation of these phenolic compounds in the defence mechanism of Citrus against P. digitatum is discussed.

Comportamento de seis variedades de pomelo (Citrus paradisi Macfad.) cultivadas sob irrigação na região semi-árida de Pernambuco

O uso da irrigação nas regiões semi-áridas do Nordeste brasileiro tem viabilizado o cultivo comercial de inúmeras fruteiras, tais como a uva, a manga, a goiaba, o coco e a banana. Outras espécies, como o pomelo, ou grapefruit, vêm sendo ainda objeto de estudos e avaliações. Uma coleção formada de 06 variedades de pomelos (Citrus paradisi), de polpas com coloração rosa-avermelhada ('Marsh Foster', 'Star Ruby', 'Rio Red' e 'Red Blush') e amarelada ('Triumph' e 'Marsh Foster Nucelar'), foi implantada em 1993 na Estação Experimental de Ibimirim, localizada no município de Ibimirim, no Vale do Rio Moxotó - região semi-árida de Pernambuco. Contando com cinco plantas por parcela, a coleção foi conduzida sob irrigação localizada e as avaliações realizadas durante três anos (2000 a 2002). Os resultados demostraram alta variabilidade na produção de frutos, tendo a variedade 'Marsh Foster Nucelar' alcançado a produção média de 135,0 kg/planta, enquanto a 'Star Ruby' atingiu apenas 31,0 kg/planta. O peso médio dos frutos variou de 285,5g ('Red Blush') até um máximo de 401,6g na variedade 'Triumph'. O volume de suco extraído, os sólidos solúveis totais (SST), a acidez total titulável (ATT) e a relação SSS/ATT também apresentaram mudanças entre as variedades estudadas.

Red Star Ruby (Sunrise) and blond qualities of Jaffa grapefruits and their influence on plasma lipid levels and plasma antioxidant activity in rats fed with cholesterol-containing and cholesterol-free diets

Bioactive compounds of peels and peeled red Star Ruby (Sunrise) and blond qualities of Jaffa grapefruits were analyzed and their antioxidant potential was assessed. The dietary fibers were determined according to Prosky et al., the total polyphenol content by Folin–Ciocalteu method and measured at 765 nm, minerals and trace elements by atomic absorption spectrometer, phenolic and ascorbic acids by HPLC and the antioxidant potential by two different antioxidant assays (DPPH and β-carotene linoleate model system). It was found that the contents of most studied bioactive compounds in both qualities are comparable. Only the contents of total polyphenols and flavonoids were higher in red grapefruits, but not significant. The antioxidant potentials of red peeled grapefruits and their peels were significantly higher than of blond peeled grapefruits and their peels ( P < 0.05 in both cases). Diets supplemented with peeled red and blond qualities of Jaffa grapefruits and their peels have increased the plasma antioxidant capacity and improved plasma lipid levels, especially in rats fed with cholesterol added diet. In conclusion, both qualities of Jaffa grapefruits contain high quantities of bioactive compounds, but the antioxidant potential of red grapefruits is significantly higher. Diets supplemented with both qualities of Jaffa grapefruits improve the plasma lipid levels and increase the plasma antioxidant activity, especially in rats fed with cholesterol added diets. Jaffa grapefruits, especially their red Star Ruby quality, could be a valuable supplementation for diseases-preventing diets.

Severity of Citrus tristeza virus Isolates from Texas

Citrus tristeza virus (CTV) isolates collected from the Lower Rio Grande Valley in south Texas and east Texas were characterized using citrus indicators and molecular methods. The citrus indicators were Mexican lime (Citrus aurantifolia), sour orange (C. aurantium), sweet orange (C. sinensis) grafted to sour orange, Duncan grapefruit (C. × paradisi), and Madam Vinous sweet orange, with some CTV isolates additionally indexed using the Texas commercial grapefruit cvs. Rio Red and Star Ruby, and Marrs and N-33 sweet orange. Severity ratings used 11 biotype groups or cumulative mean relative indices. Molecular characterization was carried out using poly- and monoclonal antibodies, seven strain-specific probes and single-stranded conformational polymorphism, and all were based on the CTV major coat protein or gene. All Texas CTV isolates produced vein clearing symptoms on inoculated Mexican lime plants. Over half of the CTV isolates tested were placed in biotype groups IX and X (causing decline of sweet orange on sour orange, seedling yellows on sour orange and grapefruit seedlings, and stem pitting of grapefruit or sweet orange), and one isolate was in biotype I (mild).

ORGANİK WASHİNGTON NAVEL PORTAKALI VE STAR RUBY ALTINTOPU YETİŞTİRİCİLİĞİNDE BİTKİ KORUMA UYGULAMALARI

This study was carried out in two different territories of Bati Akdeniz Agricultural Research Institute. The first territory is Washington Navel orange orchard and the other one is Star ruby red grapefruit orchard. The methods of conventional, integrated and organic farming were attended together in both species. Organic products of this study were certificated by ECOCERT-TURKEY, admitted internationally, and exported. It was found out that a successfull biological protection could be done in the organic parcels. For this aim beneficial insects or the combination of beneficial insects and spray oil (summer) were used against to the harmful insects (such as Planococcus citri , Dialeurodes citri , Ceroplastes floridensis , Aonidiella aurantii , A. citrina ) exceeding or having the ability of exceeding the economic loss threshold. Besides, while Bacillus thuringiensis biopreparate was used against to Ectomyelois ceratoniae and Cryptoblabes gnidiella , the mass destruction traps such as Mc Phail trap (2 number/10 tree) or Clansel bottle (3 number/10 tree) were directed to the Ceratitis capitata . However, visual yellow adhesive traps were found unsuccessfull since they catch the benefical insects. Although coppery fungicides which is one of the few inorganic compounds usable for organic farming are rather efficient against to fungal and bacterial pathogens, it is necessary to be careful for the active copper amounts lowered periodically by EU in every four years.

Effect of antioxidants and proteins on the quality of Israeli Jaffa red and blond grapefruits

Some biochemical characteristics of Israeli Jaffa Star Ruby (red) and blond grapefruits were defined using atomic absorption spectrometry, antioxidant tests and the protein electrophoretic technique. It was found that the contents of dietary fibers, major and minor minerals, phenolic and ascorbic acids in both grapefruits were without significant differences. The contents of total polyphenols, anthocyanins and flavonoids were higher in red grapefruits, but also these differences were not significant. The antioxidant capacity was determined by two modified antioxidant methods, 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonate) radical cation (ABTS⋅+) and scavenging activity against nitric oxide, and was compared with the Folin–Ciocalteu assay. The two antioxidant assays used have shown that the antioxidant potential of the Star Ruby (red) grapefruit is higher than of the blond (P<0.05) grapefruit. Proteins were extracted and separated. Some small differences were found in the sodium dodecyl sulfate–protein bands in the region of 36 kDa. Antioxidants and proteins can be used for characterization of the quality of grapefruits as a fruit diet.

Quantitation of Carotenoids in Raw and Processed Fruits in Japan

To obtain the quantitative and qualitative data available for estimating the intake of carotenoids from fruits in Japan, carotenoids were analyzed with reversed phase high-performance liquid chromatography (HPLC). Ten carotenoids were examined in 75 raw fruits and 15 processed fruits, all of which were harvested or purchased in Japan. Phytoene was detected in 58 of 90 fruit samples ; ζ-carotene, in 50 of 90 ; lycopene, in 13 of 90 ; α-carotene, in 18 of 90 ; lutein, in 56 of 90 ; β-carotene, in 80 of 90 ; β-cryptoxanthin, in 68 of 90 ; zeaxanthin, in 58 of 90 ; all-trans-violaxanthin, in 55 of 90 ; and 9-cis-violaxanthin, in 47 of 90 samples. Citrus fruits of the mandarin type (Satsuma mandarin and its hybrids, such as tangor) were rich in β-cryptoxanthin, β-carotene, all-trans-violaxanthin, and 9-cis-violaxanthin ; ‘Star ruby’ grapefruit in lycopene ; loquat, Japanese persimmon, and peach in β-cryptoxanthin, β-carotene, all-trans-violaxanthin, and 9-cis-violaxanthin ; mango in β-carotene, all-trans-violaxanthin, and 9-cis-violaxanthin ; acerolas in phytoene ; passion fruits in ζ-carotene. Carotenoid levels in common fruits, such as apple, grape, lemon, pear, strawberry, kiwifruit, cherry, pineapple, and banana, were low.

Harvest time and storage conditions of ‘Star Ruby’ grapefruit (Citrus paradisi Macf.) for short distance summer consumption

The effects of harvest date (four 3-week-spaced dates from early May to end of June) and storage temperature (6 and 10 °C) on grapefruit weight loss, decay and internal quality were evaluated at two given periods (early July and end of August). Harvest dates were before flowering (BF), at full bloom (FB), after flowering (AF) and 6 weeks after full bloom (6FB). Fruit internal quality was assessed by the percentage of juice (PJU), total soluble solids (TSS), titrable acidity (TA) and TSS:TA ratio. On orchard, between the first and the last harvest dates, PJU and TSS and TA decreased whereas TSS:TA increased sharply. PJU remained quite unchanged until after flowering, where it sharply declined leading to values near the minimum for marketing in 6FB fruit especially for small diameter ones. No clear chilling injuries were noticed even after more than 16 weeks at 6 °C. That temperature induced higher TA, lower TSS:TA ratio values and lower fruit weight loss than at 10 °C. Small diameter fruit weight loss was higher than that of large diameter fruit for both temperatures. For all harvest dates TSS, TA and TSS:TA were similar at the two tested periods for marketing (early July and end of August). By August, PJU of BF fruit was lower and close to the minimum value for marketing. Conversely, harvest date had a clear influence on decay with 30.7% of decay in BF fruit versus 5.5% in 6FB fruit by the end of experiment (end of August) mainly due to a longer storage duration and not to a higher sensitivity to decay of BF fruit. For short distance local summer marketing, we recommend to harvest grapefruit after flowering, but not too late, and to store them at 10 °C.

Fresh Israeli Jaffa blond (Shamouti) orange and Israeli Jaffa red Star Ruby (Sunrise) grapefruit juices affect plasma lipid metabolism and antioxidant capacity in rats fed added cholesterol.

The bioactivity of Israeli Jaffa blond (Shamouti) fresh orange and Israeli Jaffa red Star Ruby (Sunrise) grapefruit juices was investigated in vitro and in vivo. The contents of bioactive compounds of these juices were determined. The influence of bioactive compounds on plasma lipids and plasma antioxidant activity in rats fed cholesterol-containing and cholesterol-free diets was assessed. Significant differences in the contents of dietary fibers were not found. The contents of total polyphenols, flavonoids, and anthocyanins in fresh orange and grapefruit juices were 962.1 +/- 27.2 and 906.9 +/- 27.1; 50.1 +/- 3.3 and 44.8 +/- 3.2; and 69.9 +/- 5.6 and 68.7 +/- 5.5 microg/mL, respectively. The antioxidant potential measured by the scavenging activity against nitric oxide, the beta-carotene-linoleate model system (beta-carotene), and the 1,1-diphenyl-2-picrylhydrazyl and 2,2'-azino-bis(3-ethyl-benzothiazoline-6-sulfonic acid) diamonium salt assays was higher in orange juice but not significantly. A high level of correlation between contents of total polyphenols and flavonoids and antioxidant potential values of both juices was found. Diets supplemented with orange and to a lesser degree with grapefruit juices improved plasma lipid metabolism only in rats fed added cholesterol. However, an increase in the plasma antioxidant activity was observed in both groups. In conclusion, fresh orange and grapefruit juices contain high quantities of bioactive compounds, which guarantee their high antioxidant potential, and the positive influence on plasma lipid metabolism and plasma antioxidant activity could make fresh orange and grapefruit juices a valuable supplement for disease-preventing diets.

Reduction of postharvest rind disorders in citrus fruit by modified atmosphere packaging

Abstract Citrus fruit are relatively non-perishable, and can normally be stored for long periods of 6–8 weeks. However, the development of various types of rind disorders limits the postharvest storage capability, and causes massive commercial losses. In the present study, we found that modified atmosphere packaging (MAP) in “bag-in-box” Xtend® films (XF) effectively reduced the development of chilling injury (CI) as well as other types of rind disorders that are not related to chilling, such as rind breakdown, stem-end rind breakdown (SERB) and shriveling and collapse of the button tissue (aging). In all cases, microperforated films (0.002% perforated area) that maintained CO2 and O2 concentrations of 2–3 and 17–18%, respectively, inside the package were much more effective in reducing the development of rind disorders than macroperforated films (0.06% perforated area), which maintained CO2 and O2 concentrations of 0.2–0.4 and 19–20%, respectively. In both types of package, the relative humidity (RH) was ∼95%. No major differences were found between the effectiveness of polyethylene (PE) and XF packages, despite the fact that XF prevents water condensation inside the bags. Overall, microperforated and macroperforated XF packages reduced rind disorders not related to chilling (rind breakdown, SERB and aging) after 5 weeks of storage at 6 °C and 5 days of shelf life conditions by 75 and 50%, respectively, in ‘Shamouti’ orange, and by 60 and 40%, respectively, in ‘Minneola’ tangerines. Similarly, microperforated and macroperforated XF packages reduced the development of CI after 6 weeks of cold storage at 2 °C and 5 days of shelf life conditions by 70 and 35%, respectively, in ‘Shamouti’ oranges and by 75 and 45%, respectively, in ‘Star Ruby’ grapefruit. Furthermore, storage of unwrapped ‘Shamouti’ oranges in high RH (95%) also reduced rind disorders by 40–50%, similarly to the effects of the macroperforated films. In the light of these data, we suggest that MAP reduces the development of rind disorders in citrus fruits via two modes of action: the first, which is common to both microperforated and macroperforated films is by maintaining the fruit in a high RH environment; the second, which is specific to the microperforated film, involves maintaining a modified atmosphere environment with elevated CO2 and lowered O2 levels.

Isolation of a dehydrin cDNA from orange and grapefruit citrus fruit that is specifically induced by the combination of heat followed by chilling temperatures.

Dehydrins (DHNs; late embryogenesis abundant D-11) are a family of plant proteins induced in response to environmental stresses such as water stress, salinity and freezing or which occur during the late stages of embryogenesis. Previously, it was reported that citrus contains a small gene family encoding a unique class of dehydrins that differs from most other plant dehydrins in various respects, such as having an unusual K-segment similar to that of gymnosperms. In the present study, we identified by cDNA differential display analysis a 'Navel' orange 202-bp polymerase chain reaction (PCR) fragment, which encoded the typical plant angiosperm-type K-segment consensus sequence, and of which the expression was down-regulated by exposure to low oxygen levels. The full-length cDNA sequence of the orange DHN, designated csDHN (for Citrus sinensis DHN), was further isolated by 5'-and 3'-RACE; it had a total length of 933 bp and encoded a predicted polypeptide of 235 amino acids. In addition, the same 202-bp 'Navel' dehydrin PCR fragment was used to screen a 'Star Ruby' grapefruit flavedo cDNA library, and its full-length grapefruit homologue, designated cpDHN (for C. paradisi DHN) was isolated and found to have a total length of 1024 bp and to encode a predicted polypeptide of 234 amino acids. The defined orange and grapefruit DHN proteins were completely identical in the 196 amino acids of their N-terminus but differed in their C-terminus region. Overall, the csDHN and cpDHN proteins share 84% identity and contain the conserved dehydrin serine cluster (S-segment) and a putative nuclear localization signal, but csDHN has one conserved dehydrin K-segment consensus sequence, whereas cpDHN contains two dehydrin K-segments. Both csDHN and cpDHN represent single copy genes, in 'Navel' orange and 'Star Ruby' grapefruit genomes, respectively. We found that the cpDHN gene was consistently expressed in the fruit peel tissue at harvest, but that its message levels dramatically decreased during storage at either ambient or low temperatures. However, a pre-storage hot water treatment, given to enhance fruit-chilling tolerance, increased cpDHN mRNA levels during the first 3 weeks of cold storage at 2 degrees C, and enabled the message levels to be retained for up to a further 8 weeks of cold storage at 2 degrees C. The hot water treatment by itself had no inductive effect on cpDHN gene expression when the fruits were held at non-chilling temperatures. Other stresses applied to the fruit, such as wounding, UV irradiation, water stress, low oxygen and exposure to the stress hormone ethylene decreased DHN mRNA levels, whereas abscisic acid had no effect at all.

Response of ‘Star Ruby’ grapefruit on two rootstocks to NaCl salinity

SummaryAn experiment with seven year old field-grown ‘Star Ruby’ grapefruit trees (Citrus paradisi Macf.) grafted on ‘Cleopatra’ mandarin (Citrus reticulata Blanco (CM)) and ‘Carrizo’ citrange (C. sinensis L., Osb × Poncirus trifoliata L. Ref. (DC) (CC) was designed to evaluate the long-term effect on fruit yield (1998/2001), fruit quality and leaf mineral composition of three irrigation waters having sodium chloride concentrations of 3, 15 and 30 mM NaCl, respectively. Fruit yield was progressively decreased by salinity in all treatments, but the effect was influenced by rootstock. ‘Cleopatra’ mandarin appeared to be a better rootstock than ‘Carrizo’ citrange for ‘Star Ruby’ grapefruit trees, since in the control and in 30 mM NaCl treatment, ‘Cleopatra’ mandarin had a higher fruit yield than ‘Carrizo’ citrange. On the other hand, fruit from ‘Carrizo’ had impaired quality in the saline treatment, due to a decrease in juice percentage and an increase in pulp and peel percentage. Chloride concentration in leaves from ‘Cleopatra’ was significantly lower than for those of ‘Carrizo’. The opposite effect was observed for Na+ concentration, where leaves from ‘Carrizo’ accumulated less Na+ than those from ‘Cleopatra’. Foliar concentrations of nitrate-N were increased and K+ were decreased in the saline treatments, for trees grafted on both rootstocks.

Complexation of imazalil with beta-cyclodextrin, residue uptake, persistence, and activity against penicillium decay in citrus fruit following postharvest dip treatments.

A method for the inclusion of imazalil (IMZ) in the beta-cyclodextrin (betaCD), structural characterization of the inclusion complex and its antifungal activity against Penicillium digitatum and P. italicum assessed by in vitro and in vivo tests are reported. According to the starting stoichiometry of betaCD with respect to IMZ, an equimolar ratio beta-cyclodextrin-IMZ (betaCD-IMZ) was detected by (1)H NMR. In vitro assays showed that the freshly prepared betaCD-IMZ was as effective as IMZ, although 1- and 4-day-old betaCD-IMZ mixtures were more effective. Studies on Star Ruby grapefruit showed no significant differences in residue uptake between treatments with an IMZ commercially available fungicide (Deccozil) or betaCD-IMZ when equal active ingredient (a.i.) concentrations (250 mg/L) and dip temperatures (20 or 50 degrees C) were used. By contrast, treatments of Tarocco oranges and Di Massa lemons with 250 mg/L betaCD-IMZ at 50 degrees C produced significant differences in residue uptake in comparison with 250 mg/L Deccozil treatments at 50 degrees C. The a.i. degradation rate in grapefruit during postquarantine and simulated marketing period (SMP) at 20 degrees C was not affected by the type of formulation used, whether at 20 or 50 degrees C. Conversely, IMZ in oranges and lemons had greater persistence when applied at 50 degrees C. All fungicide treatments showed a comparable efficacy against decay in grapefruit and oranges, whereas treatment in lemons at 250 mg/L a.i. of heated fungicides had higher suppressive effects against decay than unheated chemicals having equal a.i. concentrations and comparable activity at 1200 mg/L IMZ at 20 degrees C.

Leaf and peel volatile compounds of an interspecific citrus somatic hybrid [Citrus aurantifolia (Christm.) Swing. + Citrus paradisi Macfayden

AbstractThe volatile compounds from leaves and peels of an interspecific citrus somatic hybrid, Citrus aurantifolia (Christm.) Swing. + Citrus paradisi Macfayden, obtained by fusion of protoplasts from lime, Citrus aurantifolia (cv. Mexican Lime) and grapefruit, Citrus paradisi (cv. Star Ruby), were extracted by pentane : ether (1 : 1) from liquid nitrogen ball‐milled leaves and flavedo and examined by GC–MS in comparison to those of its parents. The hybrid quantitatively retained the ability of the lime parent to synthesize in its leaves the major monoterpene aldehydes (neral, geranial) the monoterpene alcohols (nerol, geraniol), and their acetates, and also the capacity of the grapefruit parent to produce a sesquiterpene aldehyde (β‐sinensal) in its leaves and nootkatone in its peel. Conversely, synthesis of most sesquiterpene hydrocarbons and long chain aliphatic aldehydes, which are present in the lime parent leaves and peel, was strongly inhibited in the hybrid, as in the grapefruit parent. In comparison to its parents, the hybrid overproduced citronellal in its leaves and α‐sinensal and β‐sinensal in its peel. Based on these results, the future prospects for a better understanding of the inheritance mechanisms with regards to aroma biosynthesis in citrus leaves and peels are discussed. Copyright © 2002 John Wiley &amp; Sons, Ltd.

Residue levels and storage decay control in Cv. Star Ruby grapefruit after dip treatments with azoxystrobin.

Cv. Star Ruby grapefruit (Citrus paradisi Macf.) were subjected to a 3-min dip in water at room temperature (20 degrees C) or at 50 degrees C with or without 25, 50, or 100 mg/L azoxystrobin (AZX). Then, the fruits were subjected to cold quarantine at 2 degrees C and 90-95% relative humidity (RH) for 3 weeks and then stored for 5 weeks at 8 degrees C and approximately 85% RH and for another 2 weeks at 20 degrees C and 80% RH to simulate a 2-week marketing period (SMP). No AZX residues were detected in the albedo and pulp following treatments at 20 or 50 degrees C, the total amount of residues being recovered from the flavedo tissue. There was a relationship between the AZX uptake in fruit and the amount of fungicide employed at 20 or 50 degrees C. When AZX was applied to the fruit at 25 mg/L at 20 degrees C, the residue level averaged 0.11 mg/kg (active ingredient, whole fruit basis). This residue concentration increased by 50 and 75% when the application rate increased from 25 to 50 or 100 mg/L, respectively. A similar pattern of accumulation was detected in fruit subjected to treatments at 50 degrees C. However, treatments at 50 degrees C produced residue levels higher than the treatments at 20 degrees C, with increases ranging from 63 to 84%, for the same concentration. Storage conditions did not affect the amount of AZX residues in the fruit. Treatment at 50 or 100 mg/L at 20 degrees C reduced the incidence of moderate to severe chilling injury (CI). Water dips at 50 degrees C reduced the incidence and severity of CI to a very low extent, with no additional advantages when hot water was used in combination with AZX. Treatments with 50 or 100 mg/L of AZX at 20 degrees C produced beneficial effects in decay control similar to those of 25 mg/L AZX at 50 degrees C or hot water alone. Better results were achieved with 50 or 100 AZX at 50 degrees C, providing complete control of decay during cold storage and with negligible decay after SMP. It was concluded that when AZX was applied at 50 degrees C, low doses of fungicide and minimal residue levels in fruit were required to control the postharvest decay of grapefruit. This treatment does not impair fruit quality and offers very interesting prospects for large scale application, due to the reduced potential toxicity of AZX to nontarget organisms and to the environment.

Effects of combining hot water, sodium bicarbonate and biocontrol on postharvest decay of citrus fruit

SummaryChemical fungicides currently provide the primary means for controlling postharvest decay in citrus fruit. However, consumer demands for pesticide-free food and the development of pathogenic strains that are resistant to currently used fungicides necessitates the development of alternative methods for decay control. In the present study, we show that the integrated application of various “safe” postharvest treatments, including hot-water rinsing and brushing (HWB), sodium bicarbonate (SBC) (baking soda) and biocontrol by yeast antagonists, can reduce decay development almost as well as imazalil. Application of HWB (62°C for 20 s), SBC (2%, W/V) or Candida oleophila yeast cells (108 cells ml–1) 24 h after artificial inoculation of grapefruit with Pencillium digitatum (Pers.: Fr.) Sacc. reduced decay development in the infected wounds by 68, 61 or 23%, respectively. The combination of any two of these treatments or all three of them together reduced decay by 87 to 89% from the level in untreated control fruit. Similarly, HWB, SBC or yeast antagonists reduced decay development following natural infection of wounded fruit by 42, 72 and 69%, respectively. The combination of any two of these treatments or all three together reduced decay by 87 to 90% from that in control fruit. HWB and SBC had sanitizing effects and could disinfect inoculated wounds, while C. oleophila and SBC gave residual protection against later infection in the treated wounds. Postharvest storage experiments with ‘Shamouti’ orange and ‘Star Ruby’ grapefruit showed that combined treatments of HWB and yeasts, HWB and SBC, and SBC and yeasts reduced decay development by an average of 80–85% as compared with a 95% reduction observed for imazalil. Thus, the combination of different fungicide-free safe postharvest treatments may be almost as effective as commercial treatment with imazalil.