Decay Of Citrus Fruit Research Articles

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.

Induction of Resistance to Penicillium digitatum in Grapefruit by the Yeast Biocontrol Agent Candida oleophila

ABSTRACT The yeast Candida oleophila, the base of the commercial product Aspire, is recommended for the control of postharvest decay in citrus and pome fruit. Its modes of action include nutrient competition, site exclusion, and direct mycoparasitism. In the present study, we showed that application of Candida oleophila to surface wounds or to intact 'Marsh Seedless' grapefruit elicited systemic resistance against Penicillium digitatum, the main postharvest pathogen of citrus fruit. The induction of pathogen resistance in fruit was already pronounced 24 h after elicitation; it was distance, concentration, and time dependent and restricted to the peel tissue closely surrounding the yeast application site. The induction of pathogen resistance required viable yeast cells at concentrations of 10(8) to 10(9) cells ml(-1). Nonviable autoclaved or boiled yeast cells or lower yeast concentrations were ineffective in enhancing fruit disease resistance. Application of Candida oleophila cell suspensions to grapefruit peel tissue increased ethylene biosynthesis, phenylalanine ammonia lyase activity, and phytoalexin accumulation, and increased chitinase and beta-1,3-endoglucanase protein levels, indicated by western immunoblotting analysis. Scanning electron microscope observations revealed that spore germination and germ tube growth of Penicillium digitatum were markedly inhibited in wounds made near the yeast-treated sites. Overall, this study provides evidence that induced resistance against postharvest decay of citrus fruit should be considered an important component of the multiple modes of action of the yeast Candida oleophila.

Evaluation of food additives and low-toxicity compounds as alternative chemicals for the control of Penicillium digitatum and Penicillium italicum on citrus fruit.

The effectiveness of low-toxicity chemicals as possible alternatives to synthetic fungicides for the control of post-harvest green and blue moulds of citrus was evaluated. A preliminary selection of chemicals, mostly common food additives, was made through in vivo primary screenings with oranges artificially inoculated with Penicillium digitatum or P italicum. Selected compounds and mixtures were tested as heated solutions in small-scale trials. Immersion of artificially inoculated oranges or lemons for 120 s in solutions at 40.6 degrees C and natural pH of potassium sorbate (0.2 M), sodium benzoate (0.2 M) or mixtures (0.1 + 0.1 M) of potassium sorbate with sodium benzoate, sodium propionate or sodium acetate were the most effective organic acid salts tested and reduced green mould by 70-80% after 7 days of storage at 20 degrees C. The mixtures did not significantly enhance the effectiveness of potassium sorbate or sodium benzoate alone. These solutions were as effective as sodium carbonate or calcium polysulphide treatments and, in general, they were more effective on lemons than on oranges. Satisfactory control of green and blue moulds was obtained by dipping oranges for 150 s in solutions of sodium molybdate (24.2 mM) or ammonium molybdate (1.0 mM) at 48 or 53 degrees C, but not at 20 degrees C. At 53 degrees C, however, the effectiveness of hot water was not enhanced by either molybdate. Molybdenum salts at higher concentrations were phytotoxic and stained the fruit. At non-phytotoxic concentrations, the effectiveness of these solutions was more influenced by temperature than by concentration. In general, the inhibitory effects of all compounds tested were not fungicidal but fungistatic and not very persistent. In conclusion, potassium sorbate, sodium benzoate and ammonium molybdate, among the wide range of chemicals tested, were superior for the control of post-harvest Penicillium decay of citrus fruit.

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.

Impact of Ozonated Water on the Quality and Shelf-life of Fresh Citrus Fruit, Stone Fruit, and Table Grapes

Spores of fungi that cause postharvest decay of fresh fruit die rapidly in ozonated water. We determined the impact of sporocidal or higher O3 doses on fruit shelf-life and quality. Green mold and sour rot on citrus fruit, caused by Penicillium digitatum and Geotrichum citri-aurantii, respectively, were not reduced by 20 min immersion in 10 ppm O3. These fungi infect through wounds; their spores were placed in shallow wounds (l mm wide by 2 mm deep) 24 hr before treatment. On five peach varieties, the average natural incidence of brown rot, caused by Monilinia fructicola, was reduced from 10.9 to 5.4% by 1 min immersion in 1.5 ppm O3. A treatment of 15 min with 5 ppm O3 further reduced decay to 1.7%, but consistent control of brown rot was associated only with this severe treatment and it caused shallow pits on the fruit. Brown rot caused by spores placed in wounds before treatment was not controlled. Immersion for 1 or 5 min in 5 ppm O3 reduced natural aerobic bacteria populations by 1.1 and 1.6 log10 units, respectively, and yeast and filamentous fungal populations by 0.7 and 1.3 log10 units, respectively. Spores of Botrytis cinerea, cause of gray mold, were sprayed on table grape clusters, the clusters were dried, and then immersed for 1 to 6 min in 10 ppm O3. In two tests, immersion for 1 min in O3 reduced gray mold from 35% among untreated grapes to about 10%, while in two other tests the incidence was only reduced from 35 to 26%. Minor injury to the rachis of grape clusters occurred at high O3 rates. Immersion in ozonated water did not control postharvest decay of citrus fruit, injured peaches and nectarines at doses that reliably controlled decay, and on table grapes control was irregular and caused minor rachis injury at high rates.

Control of postharvest decay of citrus fruit with calcium polysulfide

Incidence of green mold of citrus, caused by Penicillium digitatum, was reduced by 80% or more by the immersion of lemons or oranges for 1‐4 min in warm (40.6‐43.3°C) ‘liquid lime-sulfur’ (LLS) solution that contained 0.75% (wt vol 1 ) calcium polysulfide. The incidence of sour rot, caused by Geotrichum citri-aurantii, was reduced 35‐70% by this treatment. LLS was similar in effectiveness to other treatments employed to control postharvest decay. Effectiveness was higher on lemons than oranges, and on green compared to yellow lemons. LLS did not stop sporulation, a benefit now obtained with some fungicides. The sulfide content of oranges, lemons, and grapefruit after LLS treatment was 31.9, 33.1, and 36.3 m gg 1 , respectively. Rigorous cleaning of fruit with water applied at high pressure after LLS treatment slightly improved LLS efficacy; conversely, similar cleaning reduces the efficacy of sodium carbonate or borax‐boric acid solutions now in use. The risk of injury to fruit by LLS was low. Fruit of one lemon and five navel orange cultivars were not visibly injured after LLS treatment for 3 min at 40.6°C followed by storage for 7 weeks at 10°C. After LLS treatment at 48.9°C, 5°C higher than needed for effective LLS use, only Lisbon lemons and Bonanza navel oranges were slightly injured. Sulfide concentration in LLS solution declined at a rate of about 7% every 24 h, this rate was similar between 25 and 65°C, and it was accompanied by the appearance of resistant deposits on the equipment. Additional losses would occur when some LLS solution is carried on fruit out of the tank. Although H2S in the air above LLS solution in pilot tests was less than 1 m ll 1 and below the worker safety threshold of 10 m ll 1 , LLS solution has an odor of H2S that can be a nuisance to workers. The disposal of used LLS solutions is more readily accomplished than other tank treatments whose disposal can be difficult because they contain synthetic fungicides, are caustic, or have a high salt concentration. Because LLS improves water penetration in soils and is commonly used for this purpose, in many locations it can be disposed of by application to agricultural soils. Published by Elsevier Science B.V.

Improved Control of Apple and Citrus Fruit Decay with a Combination of Candida saitoana and 2-Deoxy-D-Glucose.

A combination of Candida saitoana with 0.2% 2-deoxy-D-glucose to control decay of apple, lemon, and orange fruit was evaluated. Growth of C. saitoana in vitro was reduced by 2-deoxy-D-glucose; however, in apple wounds, the yeast grew as well in the presence of 2-deoxy-D-glucose as in its absence. When applied to fruit wounds before inoculation, the combination of C. saitoana with 0.2% 2-deoxy-D-glucose was more effective in controlling decay of apple, orange, and lemon caused by Botrytis cinerea, Penicillium expansum, and P. digitatum than either C. saitoana or the application of a 0.2% solution of 2-deoxy-D-glucose alone. Increasing the concentration of 2-deoxy-D-glucose from 0.2 to 0.5% did not improve control significantly. The combination of C. saitoana with 0.2% 2-deoxy-D-glucose was also effective against infections established up to 24 h before treatment. When applied within 24 h after inoculation, the combination of C. saitoana with 0.2% 2-deoxy-D-glucose was very effective in controlling blue mold of apple and green mold of orange and lemon. The level of control of green mold was equivalent to imazalil treatment. When either C. saitoana or 0.2% 2-deoxy-D-glucose was applied within 24 h after inoculation, neither had an effect on disease development on apple, orange, or lemon, and the incidence of decay was similar to the water-treated control.

Fumigation of Fruit with Short-Chain Organic Acids to Reduce the Potential of Postharvest Decay.

Vapors of acetic (1.9 or 2.5 μl/liter), formic (1.2 μl/liter), and propionic (2.5 μl/liter) acids were tested for postharvest decay control on 8 cherry, 14 pome, and 3 citrus fruit cultivars. Surfacesterilized fruit were inoculated with known fungal pathogens by drying 20-μl drops of spore suspension on marked locations on each fruit, placing at 10°C to equilibrate for approximately 24 h, and fumigating by evaporating the above acids in 12.7-liter airtight fumigation chambers for 30 min. Immediately after fumigation, the fruit were removed, aerated, aseptically injured, and placed at 20°C until decay occurred. All three fumigants controlled Monilinia fructicola, Penicillium expansum, and Rhizopus stolonifer on cherry. Formic acid increased fruit pitting on six of eight cultivars and was the only organic acid to increase blackening of cherry stems when compared to the control. Decay of pome fruit caused by P. expansum was reduced from 98% to 16, 4, or 8% by acetic, formic, and propionic acids, respectively, without injury to the fruit. Decay of citrus fruit by P. digitatum was reduced from 86 to 11% by all three acids, although browning of the fruit peel was observed on grapefruit and oranges fumigated with formic acid.

Commercial Testing of Aspire: A Yeast Preparation for the Biological Control of Postharvest Decay of Citrus

Abstract Aspire, a biocontrol product containing the yeastCandida oleophilaas the active ingredient, is registered in the United States and Israel for commercial use. The efficacy of Aspire in controlling postharvest decay of citrus fruit was evaluated in commercial packinghouse tests. The combination of Aspire with 200 μg/ml thiabendazole (TBZ) often reduced the incidence of decay, caused by the green and blue molds (Penicillium digitatumandP. italicum,respectively), as well as a conventional fungicide treatment. Furthermore, Aspire was highly efficacious against sour rot caused byGeotrichum candidum,a decay not controlled by the conventional treatments. Suppression of decay achieved with Aspire plus TBZ was maintained throughout a 5-day period during which the fruit was shipped to Europe and subsequently held in cold storage at 5°C for 45 days. However, the incidence of decay in shipped fruit was 1% greater for fruit treated with Aspire plus TBZ than for fruit that received the conventional fungicide treatment including sodiumO-phenylphenate (SOPP), TBZ, imazalil, and metalaxyl.

Reducing chilling injury and decay of stored citrus fruit by hot water dips

Abstract The effect of hot water dips (53 °C, 2–3 min) on chilling injury (CI) and decay of various citrus fruits was compared with the effect of curing (36 °C, 72 h). Experiments were conducted with grapefruit ( Citrus paradisi Macf., cv. Marsh), lemon ( Citrus limon . Burm., cv. Eureka), oroblanco ( C. grandis Osb. × C. paradisi , cv. Oroblanco, syn. Sweety) and kumquat ( Fortunella margarita Swingle, cv. Nagami). Prestorage hot water dips reduced significantly the sensitivity of all these fruits to CI. Subsequent sealing of hot water-dipped fruit improved the positive effect but was not essential for the success of treatment. In our experiments, addition of fungicides (imazalil or thiabendazole, 1000 ppm) to the hot dip did not increase significantly the CI-reducing effect, but prevented fruit decay. Hot water dip also reduced decay of citrus fruits stored both at low and optimal temperatures, demonstrating an effect comparable to that of curing. An increased level of putrescine was observed in hot water-dipped grapefruit and lemons. Compared with curing, hot water dip was much easier to implement and could be combined with regular packing-house treatment procedures.

Cylindrocladium citri . [Descriptions of Fungi and Bacteria

Abstract A description is provided for Cylindrocladium citri . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Citrus sinensis, Prunus sp. DISEASE: Decay of citrus fruits. GEOGRAPHICAL DISTRIBUTION: Japan, U.S.A (Florida). TRANSMISSION: Probably wind and splash dispersed.

Pilot Testing of Pichia guilliermondii: A Biocontrol Agent of Postharvest Diseases of Citrus Fruit

The efficacy of the yeast Pichia guillierrnondii (US-7) in controlling postharvest decay of citrus fruit was evaluated in small-scale and pilot tests in commercial packinghouses. In scale-up fermentation on cheap industrial waste materials, P. guillierrnondii grew efficiently and maintained its antagonistic activity, as tested in in vitro assay against spore germination of Penicilliurn digitatum. In small-scale experiments with injured and non-injured fruits dipped in the yeast cell suspension, the development of decay in several citrus cultivars was effectively inhibited. The yeast was compatible with a mixture of commonly used waxes containing a low concentration of a chemical fungicide. In packinghouse tests, combining the yeast with 200 ppm thiabendazole (TBZ) resulted in a reduction in the incidence of decay to a level equal to that of the commercial treatment of 2000 ppm TBZ. The efficacy of US-7 could also be maintained under packinghouse conditions at a cell concentration of the yeast antagonist as low as 107 cells/ml. No significant difference in the efficacy of P. guilliermondii was found in either the drench or the spray application systems tested in citrus packing-houses.

Combined treatment with thiabendazole and 2-aminobutane for control of citrus fruit decay

Thiabendazole and 2-aminobutane, when used as a combined treatment, show good compatibility, giving better results in the post-harvest control of green moulds of citrus fruits than treatment with either of the individual components. In addition, such a combination has a wider antifungal spectrum than each of the two components alone, is active against benzimidazole-resistant strains of Penicillium digitatum, and has the advantages of both thiabendazole and 2-aminobutane.

Supplementary Antimold Activity of Phosethyl AL, A New Brown Rot Fungicide for Citrus Fruits

AbstractPhosethyl Al (= Aliette) is a new and promising postharvest fungicide against brown rot of citrus fruits. Its effectiveness in controlling green mold (Penicillium digitaum), the major citrus fruit pathogen, was studied on artificially inoculated fruit and compared with that of sodium o‐phenylphenate (SOPP) and thiabendazole (TBZ). In vitro and in vivo experiments have shown that phosethyl Al is capable — although to a lesser extent than SOPP and TBZ — of inhibiting growth of P. digitatum and reducing the incidence of decay of citrus fruits, caused by a wild‐type, and apparently also by a benzimidazole‐resistant strain of this fungus.The influence of times of treatment and modes of application (including temperature and duration of treatment, rinsing of the fruit) on the effectiveness of phosethyl Al, SOPP and TBZ in controlling green mold was studied and discussed. It is concluded that, under conditions of natural infection, phosethyl Al can be used for the postharvest control of Phytophthora‐caused brown rot without any apparent increase in the incidence of green mold in the treated fruits.

Bestimmung pektolytischer Enzyme bei mehreren Schadpilzen von Citrusfrüchten

Abstract Characterization of pectolytic enzymes From several fungi causing post‐harvest decay of citrus fruits From culture filtrates of Penicillium digitatum Sacc., Trichoderma viride Penz., Phomopsis citri (Faw.) cf. Diaporthe citri (Faw.) Wolf, and Colletotrichum gloeosporioides Penz. endo‐polygalacturonase and endo‐polymethylgalacturonase have been isolated. Both enzymes were active under acid conditions only. The last named fungus additionally produced pectic acid‐transeliminase, the activity was found under alkaline conditions.

Effects of Cooling Versus Seal-packaging wit High-density Polyethylene on Keeping Qualities of Various Citrus Cultivars1

Abstract Seal packaging of orange [Citrus sinensis (L.) Osbeck cvs. Valencia and Shamouti], grapefruit (Citrus paradisi Macf. cv. Marsh) and lemons (Citrus limon Burnt, f. cv. Eureka) with high-density polyethylene (HOPE) film (0.01 mm in thickness) delayed softening and inhibited weight loss and deformation of the fruit more than cooling. Sealed fruit at 20°C and 85% relative humidity (RH) had better appearance and were firmer than non-sealed fruit at their lowest temperature possible without chilling injury and 85–90% RH. HOPE seal-packaging also inhibited chilling injury of grapefruit and lemons stored at 5° and 2°C, respectively. The C02 content of grapefruit was unaffected by seal-packaging, hut it was lower at cooler temperatures. Decay of citrus fruit depended more on the storage temperature than on the type of packaging. However, in storage up to 1 month, no significant difference was found in most experiments in decay percentage between orange, grapefruit, and lemon sealed with HOPE and stored in a packing house (13 to 25°C), and non-sealed fruits, at the lowest temperatures possible without chilling injury of 2, 10 and 14°C, respectively.

Pectic enzymes associated with Penicillium digitatum decay of citrus fruit

Pectic enzymes associated with Penicillium digitatum decay of citrus fruit

Citrus Fruit Decay in South Africa caused by Penicillium digitatum Sacc.

Citrus Fruit Decay in South Africa caused by Penicillium digitatum Sacc.

Sensitivity of Citrus fruit decay fungi to gamma irradiation

Dose-response curves were established for spores of seven of the most damaging Citrus fruit decay fungi. Experimental determinations were made of the doses required to inactivate every cell in a high proportion of fungus populations of various sizes. Particular attention was given to Penicillium italicum and P. digitatum, causes of the very destructive blue and green mold decays. Comparisons were made of sensitivity between irradiation in vitro and in vivo; with or without cold storage between irradiation and incubation; and between conidia and young hyphal cells.

Control of Penicillium Decay of Citrus Fruits with 2-Aminobutane

IN evaluating a number of simple aliphatic amines as volatile post-harvest fungicides for use on citrus fruits, we found that 2-aminobutane (Sec-butylamine) was remarkably effective in reducing decay incited by Penicillium digitatum Sacc.1. Subsequent experiments2 revealed that effectiveness of this amine is mainly due to the fungistatic action of butylammonium salt residues persisting on the fruit after fumigation. In vitro tests showed that germination of Penicillium spores was almost completely inhibited by 10−3 M 2-aminobutane, and, furthermore, that this inhibition could be completely reversed by washing the spores in neutral phosphate buffer, followed by transfer of the spores to amine-free medium. A number of other lower (> C6) primary monoamines were tested by this procedure and found to be ineffective in preventing spore germination. These results prompted an evaluation of 2-aminobutane in fruit washes and wax emulsions for control of Penicillium decay of citrus fruits.