The effectiveness of postharvest hot water dipping on the control of grey and black moulds in sweet red pepper (Capsicum annuum)

The effectiveness of hot water dipping on the control of grey mould, caused by Botrytis cinerea , and black mould, caused by Alternaria alternata on sweet red pepper quality was investigated. Dipping naturally infected or artificially inoculated fruit at 508C for 3 min completely inhibited, or significantly reduced, decay development caused by B. cinerea and A. alternata , respectively. Heat damage was observed on fruit dipped for 5 min at 50°C, or at 55°C for 1 min or longer. Damage appeared as cracks and pitting on the fruit surface. Spore germination and germ tube elongation in vitro was inversely related to the duration of exposure or to the range of temperature used. The ET₅₀ for spore germination for B. cinerea was 3.2, 1.5 and 0.8 min, and for A. alternata 8.8, 4.2 and 1.4 min, at 45, 50 and 55°C, respectively. The ET₅₀ for germ tube elongation for Botrytis was 2.6, 0.9 and 0.5 min, and for Alternaria , 7.2, 2.5 and 1.6 min, at 45, 50 and 55°C. The mode of action of hot water dips on decay of pepper appears to be by direct interaction with the fungi.     

Factors affecting the efficacy of post-harvest fungicide applications for the control of blue mould (Penicillium expansum) in stored apples

The effects of apple fruit maturity, temperature of fruit or dip solution, period of time in fungicidal dip, storage conditions, and spore inoculum concentration, on the efficacy of fungicides for control of blue mould ( Penicillium expansum ) were examined in various experiments.
Iprodione and imazalil were only effective when inoculum concentration was low, whilst prochloraz was highly effective in controlling rot on fruit inoculated with 3 × 10⁶ spores/ml. There was no consistent effect of dip temperature or fruit maturity on the efficacy of the fungicides. Iprodione was more effective on warm fruit (19°C) than cold fruit (6°C) whilst the reverse was true of imazalil. Extended periods of immersion in the fungicides slightly reduced the incidence of rotting but not to any useful degree.
The incidence of rotting in fruit treated with prochloraz and etaconazole was less in fruit stored under controlled-atmosphere cold storage conditions than in fruit stored in air cold-storage. Both fungicides were also effective for short-term storage at 20 C in air. Captan, benomyl, captan plus benomyl or vinclozolin were either ineffective or of poor efficacy under all storage conditions.     

Germination of Alternaria linicola conidia on linseed: effects of temperature, incubation time, leaf wetness and light regime

Conidia of Alternaria linicola germinated on both water agar and linseed leaves (detached or attached) over a wide range of temperatures (5–25°C) by producing one to several germ tubes. At temperatures between 10°C and 25°C and under continuous wetness in darkness, germination started within 2 h after inoculation and reached a maximum (100%) by 8 to 24 h, depending on temperature. At 5°C, the onset of germination was later and the rate of germ tube elongation was slower than that at 10–25°C. During germination, conidia of A. linicola were sensitive to dry interruptions of wet periods and to light. Short (2 h) or long (12 h) dry interruptions occurring at any time between 2 and 6 h after inoculation stopped conidial germination and germ tube elongation. With continuous wetness, light periods 2 to 12 h long immediately after inoculation inhibited conidial germination, which was resumed only when a dark period followed subsequently. However, germination and germ tube elongation of A. linicola conidia stopped and the viability of the conidia was lost during exposure to dry light periods immediately after inoculation with spore suspensions. Penetration of leaves by A. linicola was evident after 12 h and occurred mainly through epidermal cells (direct) with or without the formation of appressoria.     

Enhancement of Biocontrol Activity of Cryptococcus laurentii by Silicon and the Possible Mechanisms Involved

ABSTRACT Exogenous application of silicon (Si) in the form of sodium metasilicate reduced disease development caused by Penicillium expansum and Monilinia fructicola in sweet cherry fruit at 20 degrees C. The inhibition of fruit decay was correlated closely with Si concentrations. Silicon at concentrations of 1%, in combination with the biocontrol agent Cryptococcus laurentii at 1 x 10(7) cells per ml, provided synergistic effects against both diseases. Population dynamics of C. laurentii were stimulated by Si 48 h after the yeast treatment in the wounds of sweet cherry fruit. Silicon strongly inhibited spore germination and germ tube elongation of P. expansum and M. fructicola in vitro. Based on results with scanning electron microscopy, growth of both pathogens was significantly inhibited by Si in the wounds of sweet cherry fruit. Compared with the wounded water control, Si treatment induced a significant increase in the activities of phenylalanine ammonia-lyase, polyphenoloxidase, and peroxidase in sweet cherry fruit but did not increase the levels of lignin. Application of Si activated a cytochemical reaction and caused tissue browning near the site of wounding. Based on our studies, the improvement in biocontrol efficacy of antagonistic yeast when combined with Si may be associated with the increased population density of antagonistic yeast by Si, the direct fungitoxicity property of Si to the pathogens, and the elicitation of biochemical defense responses in fruit.     

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.     

Reduction of postharvest losses of Galia melon by a short hot-water rinse

A rapid method for simultaneously rinsing and disinfecting fresh harvested produce using a hot-water rinse and brushes (HWRB) was tested on Galia melon ( Cucumis melo cv. reticulatus ) fruit. The optimal treatment to reduce decay while maintaining fruit quality after prolonged storage and marketing simulation was 59 ± 1°C for 15 s. Trial shipments by sea transport to Europe demonstrated that treating melon with a commercial-scale HWRB machine (3 tonnes fruit h⁻¹) maintained significantly better overall quality of treated fruit compared with untreated fruit. Exposing spores of Alternaria alternata and Fusarium solani to 60°C for about 15 s in vitro reduced germination by 48% and 42%, respectively. Employing HWRB resulted in a 3-log reduction in total colony-forming units (CFU) of the epiphytic microbial population, compared with untreated fruit. Scanning electron microscopy (SEM) showed that HWRB removed soil, dust and fungal spores from the fruit surface, and partially or entirely sealed natural openings in the epidermis.     

Effects of Ca2+ and Mg2+ on Botrytis cinerea and Penicillium expansum in vitro and on the biocontrol activity of Candida oleophila

Calcium salts have been reported to play an important role in the inhibition of postharvest decay of apples and in enhancing the efficacy of postharvest biocontrol agents. Therefore, the present study was conducted in order to examine and compare the effects of calcium and magnesium salts on the germination and metabolism of the postharvest pathogens Botrytis cinerea and Penicillium expansum , and to determine the effects of these salts on the biocontrol activity of two isolates (182 and 247) of the yeast Candida oleophila. Increasing concentrations of CaCl₂ (25–175 mM) resulted in decreased spore germination and germ-tube growth of both pathogens. The greatest effect was observed in the case of B. cinerea. The inhibitory effect could be overcome by the addition of glucose to the germination medium. MgCl₂ (25–175 mM) had no effect on germination or germ-tube growth of either pathogen, indicating that the calcium cation rather than the chloride anion was responsible for the inhibition. The pectinolytic activity of crude enzyme obtained from the culture medium of both pathogens was also inhibited by 25–175 mM CaCl₂, with the greatest effect on the crude enzyme from P. expansum. Biocontrol activity of isolate 182 was enhanced by the addition of 90 or 180 MM CaCl₂, whereas there was no effect on the biocontrol activity of isolate 247. This was apparently due to the inability of isolate 247 to proliferate in apple wounds. It is postulated that enhanced biocontrol activity of isolate 182 of the yeast C. oleophila in the presence of Ca²⁺ ions is directly due to the inhibitory effects of calcium ions on pathogen spore germination and metabolism, and indirectly due to the ability of isolate 182 to maintain normal metabolism in the presence of"toxic" levels of calcium.     

RETRACTED ARTICLE: Effect of calcium chloride on the biocontrol efficacy of two antagonistic yeasts against <Emphasis Type="Italic">Penicillium expansum</Emphasis> on apple fruit

Two antagonistic yeasts, Candida membranaefaciens and Pichia guilliermondii, were evaluated for the control of the blue mold of apple caused by Penicillium expansum. Dual culture, cell-free metabolite and volatile tests were used for in vitro assay. Yeast strains of two genera inhibited growth of P. expansum; inhibition varied from 30.27% to 44.19% in dual culture, from 79.40% to 90.57% in the volatile metabolite test, and from 72.99% to 88.77% in the cell-free metabolite test. Calcium chloride (2% w/v) significantly inhibited the growth of the pathogen P. expansum, but did not affect the colony-forming units (CFU) of the yeasts C. membranaefaciens and P. guilliermondii in potato dextrose broth. The concentration of yeast suspension influenced spore germination and germ tube growth of P. expansum in vitro, as well as disease incidence and lesion development in fruits. There were significant negative relationships between the suspension concentrations of the yeasts and the growth as well as infectivity of the pathogen. The addition of calcium resulted in lower spore germination rates and slower growth of germ tubes in vitro, as well as in lower disease incidences and smaller lesion diameters compared with treatments with yeast antagonists alone. When yeast cell suspensions reached a concentration of 10⁷ CFU ml^-1, growth of the pathogen was completely limited in vitro, and no infection was found in apple fruits treated with or without calcium. This article has been retracted because part of the data shown has already been published before, by different authors. An erratum to this article can be found at     

Characterizing the mechanism of biological control of postharvest diseases on fruits with a simple method to study competition for nutrients

ABSTRACT Biocontrol agents may compete with pathogens for nutrients and space to delay or prevent decay of fruits after harvest. These mechanisms of biological control have been difficult to study because no method has been available to determine the significance of each of the components of competition. We developed a nondestructive method using tissue culture plates with cylinder inserts containing defusing membrane at one end to study competition for nutrients without competition for space. Other biocontrol mechanisms in which direct contact between an antagonist and a pathogen is not required also can be studied. The method was used to determine the competition between the yeastlike biocontrol agent, Aureobasidium pullulans, and Penicillium expansum for limited nutrients in apple juice during 24 h incubation, simulating a fruit wound. The antagonist depleted amino acids and inhibited germination of P. expansum conidia. Exposing these conidia to fresh apple juice increased conidial germination to the level comparable to that exhibited by conidia which were not exposed to the antagonist. Because the culture plate method was nondestructive, follow-up experiments in an agar diffusion test were conducted. Juice in which the antagonist grew did not inhibit germination of P. expansum conidia that were seeded on the plates. This corroborates findings from the culture plate method that inhibition of the conidia germination resulted from competition for nutrients. The new method can be coupled with existing techniques to improve understanding of antagonist-pathogen interaction for biological control of postharvest diseases.     

Control of post‐harvest decay of apples by pre‐harvest and post‐harvest application of ammonium molybdate

Ammonium molybdate was tested as a potential fungicide for use in apples (cv Golden Delicious) against blue and grey mould, important post‐harvest diseases of pome fruits. In tests in vivo at 20 °C, ammonium molybdate (15 mM ) reduced lesion diameters of Penicillium expansum, Botrytis cinerea and Rhizopus stolonifer by 84%, 88% and 100% respectively. When apples treated with ammonium molybdate were stored at 1 °C for three months, a significant reduction in severity and incidence of P expansum and B cinerea was observed in both years of study (1998 and 1999). In the second year of the experiment the reduction in disease severity was greater than 88% for both pathogens, and the level of control was similar to, or greater than, that observed with the fungicide imazalil. When ammonium molybdate was applied as a pre‐harvest treatment, a significant reduction in blue mould decay was observed after three months in cold storage. In vitro, ammonium molybdate greatly inhibited spore germination of P expansum and B cinerea, although better inhibition was obtained against grey mould. Ammonium dimolybdate, sodium molybdate and potassium molybdate were also tested in vitro in comparison with ammonium molybdate as inhibitors of spore germination, but only ammonium molybdate inhibited spore germination by more than 50%. © 2001 Society of Chemical Industry     

Bioassays of glucosinolate-derived isothiocyanates against postharvest pear pathogens

The present study assayed the effect of six isothiocyanates (ITCs), produced by the enzymatic hydrolysis of glucosinolates, on fungal pathogens of pear. Sample pear fruits were artificially inoculated through induced wounds with conidial suspensions of Botrytis cinerea Rhizopus stolonifer Monilinia laxa Mucor piriformis or Penicillium expansum and were then treated with ITCs. Of the six ITCs tested, the ITC from glucoraphenin showed the highest effectiveness after 6 days at 20°C, against M. laxa B. cinerea and M. piriformis . The effectiveness of the ITC from glucoraphenin against M. laxa was assayed in two further trials to test the effect of ITC concentration on different concentrations of inoculum and to determine the duration of the curative effect of this ITC. ITC concentration directly affected fungus control capacity. The highest ITC concentration (3.6 mg mL⁻¹) afforded pathogen control at the highest level of pathogen concentration (10⁶ conidia mL⁻¹) after 6 days at 20°C. Its curative effect was evident up to 40 h after inoculation.     

Effects of temperature on ascospore germination and penetration of oilseed rape (Brassica napus) leaves by A- or B-group Leptosphaeria maculans (phoma stem canker)

Ascospores of both A-group and B-group Leptosphaeria maculans germinated at temperatures from 5 to 20°C on leaves of oilseed rape. Germination of ascospores of both groups started 2 h after inoculation and percentage germination reached its maximum about 14 h after inoculation at all temperatures. Both the percentage of A-/B-group ascospores that had germinated after 24 h incubation and germ tube length increased with increasing temperature from 5 to 20°C. Germ tubes from B-group ascospores were longer than those from A-group ascospores at all temperatures, with the greatest difference at 20°C. Hyphae from ascospores of both groups penetrated the leaves predominantly through stomata, at temperatures from 5 to 20°C. A-group ascospores produced highly branched hyphae that grew tortuously, whereas B-group ascospores produced long, straight hyphae. The percentage of germinated ascospores that penetrated stomata increased with increasing temperature from 5 to 20°C and was greater for A-group than for B-group L. maculans after 40 h incubation.     

Control of postharvest pathogens and colonization of the apple surface by antagonistic microorganisms in the field

ABSTRACT Selected isolates of Aureobasidium pullulans, Rhodotorula glutinis, and Bacillus subtilis reduced the size and number of lesions on wounded apples caused by the postharvest pathogens Penicillium expansum, Botrytis cinerea, and Pezicula malicorticis. Combinations of the antagonistic microorganisms were applied to apple trees in the field late in the growing season of two consecutive years. The population dynamics of the introduced microorganisms and the incidence of fruit decay were determined. Population sizes of introduced antagonists on apple surfaces increased in the field following application of treatments until harvest. After transfer of the fruit from the field into cold storage, the populations of the introduced antagonists remained higher than in the control treatments. Identification of the applied isolates of A. pullulans and R. glutinis during the experiments was achieved by isolate-specific DNA probes generated from random amplified polymorphic DNA. A combination of two strains of A. pullulans and one strain of R. glutinis suppressed rotting of apple to the same extent as the commonly used fungicide Euparen. Our data demonstrate that the application of antagonistic microorganisms in the field represents a promising alternative to fungicide treatments to control post-harvest diseases of apple.     

Induction of Resistance to Penicillium digitatum in Grapefruit by β-Aminobutyric Acid

-Aminobutyric acid (BABA), an inducer of pathogen resistance in plants, induced disease resistance in reproductive parts of the plant, such as grapefruit peel tissue. Application of BABA to specific wound sites on the fruit peel surface induced resistance to Penicillium digitatum, the main postharvest pathogen of citrus fruit, in a concentration-dependent manner, being most effective at 20mM, and rather less effective at either higher or lower concentrations. The effect of BABA in inducing resistance to P. digitatum in the fruit peel surface was local and limited to the vicinity (within 1–2cm) of the BABA-treated site. In addition to inducing pathogen resistance, increasing concentrations of BABA (from 1 to 100mM) also exhibited direct antifungal activity and inhibited P. digitatum spore germination and germ tube elongation in vitro. The induction of resistance to P. digitatum by BABA was accompanied by the activation of various pathogen defense responses in grapefruit peel tissue, including activation of chitinase gene expression and protein accumulation after 48h, and an increase in phenylalanine ammonia lyase (PAL) activity after 72h.     

微重力对扩展青霉孢子萌发、菌丝生长和致病力的影响

 After being onto 22nd recoverable satellite of China for 18-day spaceflight under microgravity condition,me growth and pathogenicity of PeniciUium expansum were investigated.Spore germination rate of the spaceflight pathogen was insignificantly lower than that of the ground control.After germination,germ tube elongation of spaceflight pathogen was slower,as well as mycelia growth.However,there was no significant difference according to independent-samples T-test.The consistent results were obtained in vivo.The space. flight pathogen exhibited a little weaker pathogenicity in peach fruit.These findings suggested that the microgravity reduced the growth and pathogenicity of P.expansum.but the effect Was not marked.     

Effects of an Interaction Between Inoculum Density and Temperature on Germination of Puccinia allii Urediniospores and Leek Rust Progress

ABSTRACT Controlled environment experiments were conducted to study the effects of inoculum density, temperature, and their interaction on germination of Puccinia allii urediniospores and infection of leek leaves. Percent germination of P. allii urediniospores and percent branching of germ tubes increased with 3 density of urediniospores and approached a plateau for densities above approximately 20 spores cm(-2) of leaf area. Percent germination was highest at 12 to 21 degrees C, a wide-range temperature optimum. Branching occurred at temperatures ranging from 5 to 25 degrees C, but there were few germ tubes branching at 25 degrees C. P. allii successfully infected leek leaves at temperatures ranging from 7 to 22 degrees C. The number of pustules produced increased with urediniospore density on leek leaves. At low spore densities, pustule production was little affected by temperature; at higher spore densities, pustule production was greatest between 9 to 11 degrees C, and numbers of pustules decreased greatly with temperature increasing above this optimum. Latent period was affected by temperature, with latent period being shortet between 19 and 22 degrees C, and latent period increasing when temperature decreased. Latent periods became approximately 1.8 days shorter for every 10-fold increase in spore density. The rate of pustule production increased with increasing spore density on leaves and was greatest between 11 to 14 degrees C. Computer simulation of leek rust progress based on the found relationships suggested that at optimal temperatures the development of leek rust epidemics may be little affected by initial spore density and density caused by each pustule, but that at sub- and supra-optimal temperatures the development is greatly affected by these variables.     

Antifungal vapour-phase activity of allyl-isothiocyanate against Penicillium expansum on pears

The fungitoxicity of allyl-isothiocyanate (AITC) vapour against Penicillium expansum , the causal agent of blue mould on pears (cvs Conference and Kaiser), was evaluated. The best control of blue mould was obtained by exposing fruits for 24 h in a 5 mg L⁻¹ AITC-enriched atmosphere, the extent of control depending on the inoculum density. Lesion diameter was inversely related to AITC concentration. In treated fruits the percentage of infected wounds increased with conidial concentration, with fewer than 20% affected at 1 × 10³ conidia mL⁻¹ to almost 80% at 1 × 10⁶ conidia mL⁻¹. In comparison, >98% of wounds were infected in untreated fruits irrespective of conidial concentration. AITC treatments were effective up to 24 h after inoculation for Conference and 48 h for Kaiser. AITC treatments also controlled a thiabendazole-resistant strain of P. expansum , reducing the incidence of blue mould by 90% in both cultivars. The use of AITC produced from pure sinigrin or from Brassica juncea defatted meal may be an economically viable alternative to synthetic fungicides against P. expansum .     

Diversity and population dynamics of Penicillium spp. on apples in pre- and postharvest environments: consequences for decay development

Isolates of Penicillium spp. were collected regularly from 2001 to 2003 from the surfaces of apple fruit pre- and postharvest, and from the atmosphere of orchards and storage rooms in France. Penicillium spp. were not detected from the atmosphere of conventional orchards, while their density did not exceed 50 spores m⁻³ in the atmosphere of organically managed orchards. Penicillium spp. were seldom detected on apple surfaces in the orchard. The density of Penicillium on apples increased from 10 to 50 spores cm⁻² after 1 month in storage to 300–400 spores cm⁻² after 6 months. The level of airborne Penicillium increased by up to 2 × 10⁴ and 2·5 × 10³ spores m⁻³ within nondisinfected and previously disinfected warehouses, respectively. Penicillium expansum (30–62%) and P. solitum (6–45%) were the most prevalent species on apple or in storage rooms. Other species of Penicillium isolated included P. commune, P. verrucosum, P. chrysogenum, P. rugulosum and P. digitatum. Apple fruit were also surveyed for wounds and the number of open lenticels using the sulphur dioxide test. The incidence of wounding at harvest varied from 12 to 36%, depending on cultivar and locality. When apples were inoculated at harvest by either aqueous or aerial inoculum of P. expansum, the decay incidence was constantly higher than the incidence of wounding. The number of open lenticels per cm² of apple surface varied from 0·5 on cv. Boskoop to 4·4 on cv. Golden Delicious. An average of 13 and 2·1% of lenticels, respectively, were infected when they were inoculated by P. expansum and P. verrucosum. Cultivars of apple fruit that showed a greater number of open lenticels, combined with a large diameter varying from 100 to 200 µm, were more susceptible to P. expansum.     

Influence of Nutrient and Environmental Factors on Conidial Germination of Potebniamyces pyri

ABSTRACT Potebniamyces pyri is the causal agent of Phacidiopycnis rot, a postharvest disease of pears. Infection of fruit occurs in the orchard, and symptoms develop during storage. Conidial germination of P. pyri in response to nutrient, temperature, wetness duration, relative humidity (RH), and pH was determined in vitro. Conidia germinated by either budding or developing germ tubes in various concentrations of pear juice solutions. The mode of conidial germination was nutrient-dependent. Low nutrient levels favored budding, whereas high nutrient levels favored germ tube development. Conidia germinated at 0 to 30 degrees C but not at 35 degrees C, with optimum temperature between 20 and 25 degrees C. Wetness durations of 4 to 5 h and 6 to 8 h at optimum temperature were required for budding and developing germ tubes, respectively, and 20 to 24 h of wetness was required to reach germination peaks. Regardless of temperature, conidia germinated primarily by budding in 10% pear juice. Secondary conidia, produced by budding of conidia, initially increased their dimensions and later germinated at 0 to 25 degrees C in the same manner as mother conidia. No germination of secondary conidia occurred at 30 degrees C. Germ tubes from conidia elongated at 0 to 25 degrees C but not at 30 degrees C. No germination occurred at 相似文献