Effect of modified atmosphere packaging on overall appearance and nutraceutical quality of pot marigold held at 5 °C.

The effectiveness of passive modified atmosphere packaging (MAP) on chemical and quality properties of calendula flowers was studied during ten days of storage at 5 °C. Weight loss of flowers wrapped with continuous and micro-perforated-films (2-3%), was significantly lower than control (unwrapped flowers) (about 30%) and those wrapped with macro-perforated film (about 7%). At the end of storage unwrapped flowers were judged unmarketable being severely wilted and shriveled, while all packaged ones were still fresh and marketable. On day 10, the fructose concentration of control flowers decreased by 74%. Continuous and micro-perforated films delayed the decline of fructose concentration over storage. Sucrose concentration decreased with storage in control flowers, while in continuous film wrapped flowers it increased. After 10 d of storage, the total phenols' concentration of all packaged flowers was significantly higher than control and similar to the initial value (2.58 ± 0.02 g 100 g-1 d.w.). Thirteen carotenoids were identified by HPLC-MS. The initial ß carotene concentration (65.72 ± 0.09 mg 100 g-1 d.w.) did not change in flowers wrapped with macro- and micro-perforated films, in contrast to the other treatments. Lycopene concentration strongly decreased in control flowers, while minor losses occurred in packaged ones. Laser micro-perforated film, being a good compromise between humidity retention inside the packages and the permeability of the film, seems to be the best choice to extend the storage life of calendula flowers.

Changes in physiological and some nutritional, nutraceuticals, chemical-physical, microbiological and sensory quality of minimally processed cactus pears cvs 'Bianca', 'Gialla' and 'Rossa' stored under passive modified atmosphere.

BACKGROUND: The objective of this study was to compare the overall quality changes of minimally processed cactus pears cvs 'Bianca', Gialla' and 'Rossa' stored at 4 °C for 10 days. Periodically in-package CO2 , O2 and C2 H4 were determined and fruit were assessed for overall quality changes (pH, acidity, sugars, phenolics, betacyanins and betaxanthines, antioxidant capacity, colour, firmness, microbiological population and sensory attributes). In a preliminary study three different polymeric films were tested to select the most suitable to design a package with a short lag time to achieve steady-state conditions. RESULTS: Results showed marked differences between measured in-package CO2 and O2 values and those calculated based on respiration of peeled fruit and film permeance to CO2 and O2 provided by manufactures. The sensory evaluation of packed fruit indicated in film BBT-Bolphane, which created a steady-state in-package partial pressure for CO2 of 4.3-4.8 kPa and for O2 of 4.8-5.5 kPa, as the best film. Results of in-package gas composition with the three cultivars were similar to those achieved in cv. 'Gialla' with the preliminary test. All measured qualitative parameters changed slightly over the storage period for all cultivars and followed the same trend, despite significant differences existing among cultivars. CONCLUSION: This study clearly showed a similar physiological behavior of minimally processed 'Bianca', 'Gialla' and 'Rossa' cactus pears. Storage conditions optimal for one cultivar fit well for the others; thus mixing fruit of different cultivars in a package designed for one specific cultivar does not lead to relevant deviation from expected results. © 2017 Society of Chemical Industry.

Biocontrol of Monilinia laxa by Aureobasidium pullulans strains: Insights on competition for nutrients and space.

Two Aureobasidium pullulans strains (L1 and L8), able to prevent postharvest fruit decay, were evaluated in order to elucidate how the competition for nutrients and space was involved in their activity against Monilinia laxa, the causal agent of peach brown rot. The competition for nutrients was studied by co-culturing pathogen conidia and antagonists in different conditions of nutrient availability and avoiding contact between them. Both antagonists prevented the germination of conidia of M. laxa in water, reducing germination rate by >35%. However, L1 and L8 showed the lowest inhibition of conidial germination in peach juice at 5%, with a reduction of 12.6% and 13.9% respectively. HPLC amino acid analysis of peach juice revealed that the addition of the yeast suspension greatly modified their composition: asparagine was completely depleted soon after 12h of incubation and was probably hydrolyzed to aspartic acid by the yeasts, as aspartic acid content markedly increased. Pure asparagine and aspartic acid were tested by in vitro trials at the concentrations found in peach juice: both influenced M. laxa growth, but in opposite ways. Asparagine stimulated pathogen growth; conversely, amended medium with aspartic acid significantly inhibited the conidia germination and mycelial development of M. laxa. Scanning Electron Microscopy revealed that both strains showed a great capability to compete with M. laxa for space (starting 8h after treatment), colonizing the wound surface and inhibiting pathogen growth. This study clearly showed that A. pullulans L1 and L8 strains could compete with M. laxa for nutrients and space; this mode of action may play an important role in the antagonistic activity, especially in the first hours of tritrophic host-pathogen-antagonist interaction, although several other mechanisms can interact each other.

Combined effects of potassium sorbate, hot water and thiabendazole against green mould of citrus fruit and residue levels.

Postharvest treatments of potassium sorbate only controlled recently established infections of Penicillium digitatum on Femminello siracusano lemons but did not confer any persistent protection. The loss of efficacy of potassium sorbate to control green mould decay was related to its irregular deposition on the fruit surface, as revealed by environmental scanning electron microscopy of oranges, and to the brief persistence of potassium sorbate residues. When treatment was done at 53°C, the co-application of potassium sorbate with thiabendazole reduced thiabendazole residues in Moro and Sanguinello oranges, compared to thiabendazole treatment alone. However, treatment efficacy against two isolates of P. digitatum (thiabendazole-sensitive and thiabendazole-resistant) notably improved, indicating that potassium sorbate and hot water potentiated thiabendazole activity. Potassium sorbate residues remarkably decreased during fruit storage and were not affected by the co-application of thiabendazole.

Residue levels and efficacy of fludioxonil and thiabendazole in controlling postharvest green mold decay in citrus fruit when applied in combination with sodium bicarbonate.

The curative and protective activity of sodium bicarbonate (SBC) at 1% alone or in combination with fludioxonil (FLU), thiabendazole (TBZ), or FLU and TBZ together, between 50 and 600 mg/L, was evaluated on fruit of different citrus species and cultivars. Fruits were either artificially inoculated with a resistant (TBZ-r) or sensitive (TBZ-s) strain of Penicillium digitatum or not inoculated and incubated at 20 °C and 90% relative humidity (RH) for 7 days (incubated fruit) or stored at 1.5 °C for 21 days plus 7 days of simulated marketing conditions at 20 °C and 60% RH. The effectiveness of these treatments was related with treatment-induced changes of epicuticular wax morphology, the mode of distribution of SBC, TBZ, and FLU on the fruit surface, and FLU and TBZ fruit residue levels. SBC alone showed a weak activity against both strains of P. digitatum. Both TBZ and FLU were very effective at all rates used, and their activity markedly increased when combined together or with SBC, even at concentrations of 50-150 mg/L. Fruit treated with SBC either alone or in combination with TBZ and/or FLU increased weight loss, although no treatment damage was detected. Residue levels of TBZ generally increased when TBZ was combined with FLU and/or SBC, whereas those of FLU slightly increased only in treatment where FLU was combined with TBZ and SBC. Initial residues of TBZ and FLU when applied at 600 mg/L were around 2 and 1 mg/kg, respectively, several times below the lowest MRLs set by most important citrus-producing countries. In treatments with SBC or SBC plus TBZ or FLU, SEM observation of the fruit surface showed a smoothing of cuticular wax platelets' surface, whereas ESEM micrographs showed irregular spots of salt deposits of roundish to irregular shape. The apparently uneven distribution of SBC or SBC plus TBZ or FLU or SBC plus TBZ and FLU on fruit might in part reduce the potential beneficial effects of SBC or of fungicide-SBC mixtures.

Control of postharvest diseases of fruit by heat and fungicides: efficacy, residue levels, and residue persistence. A review.

Extensive research has been done in recent years to reduce the heavy dependence on chemical fungicides to control postharvest diseases and disorders of horticultural crops. Alternative strategies were based on improved cultural practices, biological control, plant-defense promoters, and physical treatments such as UV illumination, radiofrequency treatment, heat therapy, and storage technologies. Among these, postharvest heat treatments such as hot water dips, short hot water rinsing and brushing, and hot air conditioning have reduced rot development and enhanced fruit resistance to chilling injury in sensitive cultivars while retaining fruit quality during cold storage and shelf life. Additive or synergistic increases in effectiveness were observed by integrating heat therapy with various chemical compounds, thus leading to significant reductions in the application of active ingredients to protect produce from decay. This paper highlights the knowledge on this topic with emphasis on heat therapy effects and factors affecting the uptake, persistence, and performance of fungicide residues when they are applied in combination with hot water.

Postinfection activity, residue levels, and persistence of azoxystrobin, fludioxonil, and pyrimethanil applied alone or in combination with heat and imazalil for green mold control on inoculated oranges.

The postinfection activity of azoxystrobin (AZX), fludioxonil (FLU), and pyrimethanil (PYR), applied alone or in combination with imazalil (IMZ), in controlling postharvest green mold in 'Salustiana' oranges inoculated with Penicillium digitatum was studied. Fruits were immersed for 30 or 60 s in (i) water or water mixtures at 20 degrees C containing AZX, FLU, or PYR at 600 mg/L; and (ii) IMZ at 600 mg/L, alone or in combination with AZX, FLU, or PYR at 600 mg/L. Similar treatments were performed at 50 degrees C using the active ingredients at half rates with respect to the treatments at 20 degrees C. Fungicide residues in fruits were analyzed following treatments and after 14 days of simulated shelf life at 17 degrees C. AZX or FLU mixtures at 20 degrees C for 30-60 s similarly but moderately reduced green mold decay with respect to control fruit; differences due to dip time were not significant. Superior control of decay was achieved by PYR and, especially, IMZ, applied alone or in combination with AZX, FLU, or PYR. The activity of PYR at 20 degrees C was significantly dependent on treatment time, whereas that of IMZ and combined treatments at 20 degrees C was not. The effectiveness of FLU or PYR mixtures at 50 degrees C in controlling decay was similar and superior to that of AZX. The action of single- or double-fungicide application was not dependent on dip time in most samples. IMZ or combined mixtures at 50 degrees C were consistently more effective with respect to single-fungicide treatments with AZX, FLU, or PYR. The application of heated fungicide mixtures resulted in significantly higher residue accumulation in most fruit samples compared to treatments performed at 20 degrees C. The degradation rate of fungicides was generally low and dependent on treatment conditions such as time, temperature, and the presence or not of other fungicides.

Influence of post-harvest application rates of cyprodinil, treatment time and temperature on residue levels and efficacy in controlling green mould on 'Valencia' oranges.

The effectiveness of heat treatments with water and cyprodinil in controlling post-harvest green mould caused by Penicillium digitatum was investigated on artificially inoculated 'Valencia' oranges. Residue levels of cyprodinil were determined in the oranges as a function of active ingredient concentration, temperature and treatment time. Cyprodinil residues were significantly dependent on treatment time when applied at 600 mg l(-1) and 20 degrees C, but not when fruit were treated at 150-300 mg l(-1). The application of cyprodinil at 50 or 100 mg l(-1) at 55 degrees C for 30 s produced similar residue levels, while residues increased when the application rate was 150 mg l(-1). Cyprodinil at 100 mg l(-1) and 60 degrees C produced a significant increase in residues compared to treatment at 50 mg l(-1); no significant increase in residues was found when the application rate was raised from 100 to 150 mg l(-1). In comparison to treatments performed at 20 degrees C, the application of a heated cyprodinil mixture resulted in significantly higher residues in fruit. All treatments with cyprodinil at 20 degrees C similarly reduced green mould after 7 days of storage at 20 degrees C. After 18 days, treatment with cyprodinil at 600 mg l(-1) for 30 s was more effective than at 150-300 mg l(-1). When dip time was extended to 90 or 180 s, treatment efficacy was positively related to fungicide concentration. Treatments with water at 55 degrees C for 30 s were as effective as cyprodinil at 50-100 mg l(-1), but less effective than cyprodinil at 150 mg l(-1). After 7 days, treatment with water or cyprodinil at 50-150 mg l(-1) and 60 degrees C were equally effective in controlling green mould; while, after 18 days, treatment with cyprodinil at 150 mg l(-1) was consistently more effective than at 50-100 mg l(-1) or hot water alone.

Factors affecting the synergy of thiabendazole, sodium bicarbonate, and heat to control postharvest green mold of citrus fruit.

The efficacy of thiabendazole (TBZ) to control postharvest decay caused by Penicillium digitatum of citrus fruit can be enhanced by co-application with sodium bicarbonate (SBC) and/or heat treatment. The impact of these treatments was investigated in citrus fruit, as a function of TBZ and SBC concentration and temperature, and were related to the amount of TBZ residues in fruit (total residues), in fruit surface, in the cuticular wax, and in the inner fruit. The residue levels of TBZ were determined in 'Valencia' oranges following a 1 min dip in an aqueous mixture of SBC at 0.5, 1, or 2 wt %/vol and TBZ at 600 or 400 mg/L (active ingredient, a.i.) at 20 or 40 degrees C and after 0 and 20 days at 17 degrees C and 90% relative humidity. The influence of SBC and heat on the TBZ residue concentration on the fruit surface, in cuticular wax, and on the inner cuticle tissue was determined in 'Salustiana' oranges after a 1 or 3 min dip in TBZ alone at 600 mg/L and 20 or 50 degrees C or for 1 min in TBZ at 600 mg/L and SBC at 2% and 20 degrees C. The efficacy of heat treatments with water, SBC, and TBZ, applied separately or in combination, was investigated on artificially inoculated 'Nova' mandarins and 'Valencia' oranges for the control of postharvest green mold caused by a TBZ-sensitive (TBZ-s) or TBZ-resistant (TBZ-r) isolate of P. digitatum. The residue levels of TBZ in fruit, evaluated as total residues, were not affected by the co-application of SBC in most samples. While TBZ residues in the fruit surface were not significantly affected by the dip temperature or by co-application of SBC, the rates of diffusion and penetration of TBZ into cuticular wax markedly increased in the presence of SBC or when TBZ was applied in combination with heat. TBZ residues in the inner tissue of fruits treated at 20 degrees C were not dependent upon the dip time or by the presence of SBC and were similar to those found in fruit treated with TBZ at 50 degrees C for 1 min, whereas significantly higher values were recorded in samples treated with TBZ at 50 degrees C for 3 min. When TBZ at 600 mg/L and 20 degrees C was applied in the presence of SBC at concentrations of 1-2 or 0.5-2%, it effectively reduced decay caused by the TBZ-resistant isolate of green mold in 'Nova' mandarins and 'Valencia' oranges. This treatment was also significantly more effective than TBZ alone to control green mold caused by a TBZ-s isolate in 'Valencia' oranges. The combination with SBC and mild heat (40 degrees C) and TBZ at 400 mg/L generally improved the control of a TBZ-r isolate of green mold with respect to the combined treatment at 20 degrees C. TBZ efficacy was also improved when applied at reduced rates (200 mg/L) and 50 degrees C, significantly suppressing green mold caused by a TBZ-s isolate of P. digitatum and effectively controlling a TBZ-r isolate. The rate of weight loss of 'Valencia' oranges was significantly increased by SBC treatment and was positively dependent upon the concentration of SBC used in the treatment, while the temperature of the treatment solution had little influence on later weight loss.

Efficacy of heat treatments with water and fludioxonil for postharvest control of blue and gray molds on inoculated pears and fludioxonil residues in fruit.

The residue levels of fludioxonil (FLU) were determined in pear cultivars Precoce di Fiorano, Coscia, and Spadona estiva after a 2-min dip in an aqueous mixture of FLU containing 300 or 100 mg/liter of active ingredient at 20 or 50 degrees C and after 12 days at 17 degrees C and 80% relative humidity (simulated shelf life conditions). The accumulation trend of FLU residues was determined in 'Precoce di Fiorano' pears after treatments with 25, 50, 100, or 200 mg/liter of active ingredient at 20 or 50 degrees C for 2 min or at 60 degrees C for 1 min. The efficacy of heat treatments with water and FLU was investigated on artificially inoculated 'Precoce di Fiorano', 'Coscia', and 'Spadona estiva' pears for the control of postharvest blue mold and gray mold caused by Penicillium expansum and Botrytis cinerea, respectively. Treatment with 300 mg/liter FLU at 20 degrees C resulted in residue levels similar to those from treatment with 100 mg/liter FLU at 50 degrees C in 'Coscia' fruit but in significantly lower residues in 'Precoce di Fiorano' and 'Spadona estiva' pears. Post-shelf life residues decreased in all cultivars, especially in 'Spadona estiva' pears treated with 300 mg/liter FLU at 20 degrees C. Residue levels of FLU in 'Precoce di Fiorano' pears treated at 20, 50, or 60 degrees C were correlated with fungicide dosage. When an equal rate was used, treatment at 50 degrees C resulted in a higher and a notably higher FLU deposition than that found under treatment at 60 and 20 degrees C, respectively. The in vitro tests showed that both pathogens were very sensitive to FLU, with MICs averaging 0.05 and 0.1 mg/liter for B. cinerea and P. expansum isolates, respectively. The 50% effective concentration ranged between 0.01 and 0.05 mg/liter for B. cinerea and between 0.05 and 0.1 mg/liter for P. expansum. In the in vivo trials, hot water treatment effectively reduced the incidence of both diseases during the first 4 to 8 days, depending on cultivar, dip temperature, and type of inoculum. However, as the incubation time proceeded, decay reduction was generally lower and the benefit of heat treatments was notably reduced or almost lost. In contrast, all treatments with FLU had a long-lasting effect. Treatments with heated FLU were more effective than those with unheated FLU; reduced concentrations of active ingredient were required to achieve a comparable control of blue and gray mold decay in these pears.

Influence of postharvest hot water treatment on nutritional and functional properties of kumquat (Fortunella japonica Lour. Swingle Cv. Ovale) fruit.

The present study investigated the influence of a hot water dip (HWD) for 2 min at 50 degrees C, a standard and effective treatment for postharvest decay control of citrus fruit, on the nutritional and health-related properties of kumquats. The results show that most of the parameters examined, including titratable acidity, soluble solids content, maturity index, glucose, fructose, sucrose, ascorbic acid, dehydroascorbic acid, alpha- and gamma-tocopherols, beta-carotene, zeaxantin, rhoifolin, and antioxidant activity, were not significantly affected by treatment. The levels of beta-cryptoxanthin, narirutin, and total flavonoids increased after HWD, whereas lutein and total phenols decreased. The concentration of the essential oil and the relative percentage of the individual components of the essential oil were not affected by HWD except for the minor compound p-menta-1,5-dien-1-ol, which increased after HWD. After storage, lower levels of glucose, total sugars, beta-carotene, beta-cryptoxanthin and lutein were recorded in HWD fruit. A decrease in antioxidant activity and increases in alpha-tocopherol and total vitamin E were found both in control and HWD fruit. The influence of HWD at 50 degrees C for 2 min on individual nutraceuticals and health-related properties was thus generally low and may depend on storage conditions.

Residue levels and storage responses of nectarines, apricots, and peaches after dip treatments with fludioxonil fungicide mixtures.

Mature apricots (Prunus armeniaca), nectarines [Prunus persica var. nectarine (Ait.)], and peaches [P. persica (L.) Batsch.] were subjected to a 2 min dip treatment with warm water at 48 degrees C or with fludioxonil (FLU) at 100 mg L-1 and 20 degrees C or at 25 mg L-1 FLU and 48 degrees C and then stored at 5 degrees C and 90-95% relative humidity (RH) for 1 week plus 1 additional week at 18 degrees C and approximately 80% RH. Fruit residue uptake was determined as a function of fungicide concentration, dip temperature, treatment time (only on nectarines), and fruit storage conditions. FLU residue level was closely related to fungicide concentration and treatment temperatures and was dependent on fruit species. FLU residues showed great persistence over both storage and shelf life. Fruit dipping in water at 48 degrees C effectively reduced decay development in cvs. 'May Grand' nectarines and 'Pelese' apricots but was ineffective in cvs. 'Red Top' and 'Sun Crest' nectarines during 7 days of storage compared with nontreated fruit. Decay rates in cvs. 'Glo Haven' peaches and 'Fracasso' apricots were very low in fruit dipped in water at both 20 and 48 degrees C. Fungicide treatments at 20 and 48 degrees C resulted in the total or almost total suppression of decay in all cultivars. During shelf life, fruit became very prone to decay, averaging 25.7-100% depending on the cultivar. Fruit dipping in hot water effectively reduced decay in 'Pelese' and 'Fracasso' apricots, 'Sun Crest' peaches, and 'May Grand' nectarines as compared to control, but was ineffective in 'Glo Haven' and 'Red Top' peaches. Fungicide treatments at 20 degrees C were more effective than hot water in most cultivars. The combination of FLU with water at 48 degrees C further improved the fungicide performance. Indeed, reduced levels (a fourth) of active ingredient were required to achieve a control of decay comparable to that for treatment at 20 degrees C. Residue levels in fruit after treatment with 100 mg L-1 FLU at 20 degrees C or with 25 mg L-1 FLU at 48 degrees C averaged approximately 0.6-2 mg kg-1, which were notably lower than the maximum residue limit (5 mg kg-1) allowed in the United States for stone fruit.

Residues of the quinone outside inhibitor fungicide trifloxystrobin after postharvest dip treatments to control Penicillium spp. on citrus fruit.

The effectiveness of postharvest dip treatment with trifloxystrobin (TFX) or imazalil (IMZ) was compared for controlling green and blue mold (caused by Penicillium digitatum and Penicillium italicum, respectively) of citrus fruit. Residues retained by fruit were determined as a function of treatment time, dip temperature, and storage conditions. Trials on 'Avana apireno' mandarin oranges artificially inoculated with P. digitatum or P. italicum revealed that treatments with 200 to 600 mg/liter active ingredient TFX at 20 degrees C were less effective than 100 mg/liter TFX at 500C for controlling P. digitatum but equally effective for controlling P. italicum. IMZ treatments with 200 mg/liter IMZ at 20 degrees C or 25 mg/liter IMZ at 50 degrees C resulted in more than 98% reduction of P. digitatum and ca. 93% reduction of P. italicum compared with untreated fruit. Total suppression of pathogens was achieved when higher IMZ doses were applied. Studies on artificially wounded lemons, oranges, clementines, and mandarins revealed that treatment with 100 mg/liter TFX at 50 degrees C effectively controlled decay development (mainly due to P. digitatum) after 7 days of storage at 20 degrees C. These results were confirmed on nonwounded oranges of cv. Tarocco and on grapefruits of cvs. Marsh Seedless and Star Ruby during 3 weeks of simulated quarantine at 1 degrees C, storage (5 weeks at 8 degrees C for oranges and 8 weeks at 11degrees C for grapefruits), and an additional 1 week of simulated marketing conditions at 20 degrees C. IMZ at 50 degrees C was highly effective for controlling decay during storage and the simulated marketing period. TFX treatment at 50 degrees C was as effective as IMZ for controlling decay in most samples. After treatment with 100 mg/liter TFX at 20 degrees C, fungicide residues in 'Tarocco' oranges doubled from 0.15 mg/kg to 0.30 mg/kg when dip time increased from 0.5 to 3 min, whereas when treatments were performed at 50 degrees C TFX residues were not related to dipping time. Residues of TFX were significantly correlated with dip temperature. A 3-min dip treatment at 50 degrees C resulted in a deposition of TFX that was approximately twofold higher than that obtained when treatments were carried out at 20 degrees C.

Residue levels and effectiveness of pyrimethanil vs imazalil when using heated postharvest dip treatments for control of Penicillium decay on citrus fruit.

The influence of fungicide concentration and treatment temperature on residue levels of pyrimethanil (PYR) in comparison with the commonly used fungicide imazalil (IMZ) was investigated in orange fruits following postharvest dip treatments. The dissipation rate of PYR residues was recorded as a function of storage conditions. The fungicide efficacy against green and blue molds caused by Penicillium digitatum and Penicillium italicum, respectively, was evaluated on different citrus varieties following the fungicide application at 20 or 50 degrees C. Residue levels of PYR in Salustiana oranges were significantly correlated with the fungicide dosage, but residue concentrations were notably higher (ca. 13-19-fold) after treatment at 50 degrees C as compared to treatments at 20 degrees C. After treatment at temperatures ranging from 20 to 60 degrees C, PYR and IMZ residues in Salustiana oranges were significantly correlated with dip temperatures. Dissipation rates of PYR during storage were negligible in both Salustiana and Tarocco oranges. Results obtained on wounded, noninoculated Miho satsumas revealed that when treatments were performed at 50 degrees C, PYR or IMZ concentrations needed to achieve the complete control of decay were 8- and 16-fold less than by treatment at 20 degrees C. When fruits were inoculated with either P. digitatum or P. italicum, the application of 400 mg L(-1) PYR at 20 degrees C or 100 mg L(-1) PYR at 50 degrees C similarly reduced green and blue mold development. These results were corroborated by storage trials on Marsh grapefruits and Tarocco oranges. The lowest concentration of PYR required to achieve almost total protection of the fruit against decay accounted for 100 mg L(-1) at 50 degrees C and 400 mg L(-1) at 20 degrees C, respectively. Treatments did not affect fruit external appearance, flavor, and taste. It is concluded that postharvest PYR treatment represents an effective option to control green and blue mold in citrus fruit and that integration of fungicide applications and hot water dips may reduce the possibility of selecting fungicide-resistant populations of the pathogen, as a consequence of increased effectiveness of the treatment.

Residue level, persistence, and storage performance of citrus fruit treated with fludioxonil.

The potential of postharvest dip treatments with fludioxonil (FLU) (a synthetic analogue of the bacterial metabolite of pyrrolnitrin), in controlling postharvest decay caused by Penicillium digitatum and Penicillium italicum of citrus fruit was investigated in comparison with the conventional fungicide imazalil (IMZ). The ultrastructural changes of fruit epicuticular wax was investigated as a function of water dip temperature, and the possible role of these changes was related to residue accumulation under FLU treatment. Residues retained by fruit were determined as a function of fungicide concentration, dip temperature, and fruit storage conditions. Scanning electron microscopy analysis revealed that fruit dipping in water at 30 or 40 degrees C did not cause differences in cuticular wax's ultrastructure in comparison to control fruit, while treatments at 50, 55, or 60 degrees C caused the disappearance of wax platelets, resulting in relatively homogeneous skin surface, due to partial "melting" of epicuticular wax. Residues of FLU in fruit treated at 20 or 50 degrees C were significantly correlated with the doses of fungicide applied. When equal amounts of fungicide were employed, the residue concentrations were notably higher (from 2.6- to 4-fold) in fruit treated at 50 degrees C than in fruit treated at 20 degrees C. The dissipation rate of FLU in "Salustiana" and "Tarocco" oranges was lower in fruit subjected to treatment at 50 degrees C. The minimal FLU concentration for almost complete decay control in artificially wounded fruit during 7-d storage at 20 degrees C was 400 mg/L active ingredient (ai) in fruit treated at 20 degrees C and 100 mg/L ai in fruit treated at 50 degrees C. Results on nonwounded Tarocco oranges subjected to 3 weeks of simulated quarantine conditions at 1 degrees C, plus 6 weeks of standard storage at 8 degrees C and an additional two weeks of simulated marketing period (SMP) at 20 degrees C revealed that almost complete decay control with FLU applications of 100 mg/L at 50 degrees C and 400 mg/L at 20 degrees C resulted in ca. 0.8 mg/kg FLU fruit residues, in agreement with results on wounded citrus fruit. When equal concentrations and temperatures were applied, FLU treatments were as effective as IMZ. In vitro trials showed a low sensitivity to FLU against P. digitatum and P. italicum isolates. MIC values for the complete inhibition of mycelium growth were >or=100 microg/mL, while ED(50) values ranged from 0.1 to 1 microg/mL for P. digitatum and from 1 to >100 microg/mL for P. italicum. The latter result suggests that care should be taken to avoid exclusive application of FLU in a sustainable program for management of fruit decay. However, integrating fungicide application and hot water dip may reduce the possibility of selecting fungicide-resistant populations of the pathogen, by increasing the effectiveness of the treatment.