Control Of Blue Mold Research Articles

Screening of core microorganisms in healthy and diseased peaches and effect evaluation of biocontrol bacteria (Burkholderia sp.)

Biological antagonists serve as the most important green alternatives to chemical fungicides, a class of microorganism that inhibits the growth of pathogenic fungi to reduce fruit incidence. In this paper, healthy and diseased peach fruit was selected for amplicon sequencing of the epiphytic microbiota on their surface to obtain a comprehensive understanding. Community structure, diversity and LefSe analysis were performed to screen Acetobacter, Muribaculaceae and Burkholderia as the core bacteria, Mycosphaerella, Penicillium and Alternaria as the core fungi, they showed significant differences and were highly enriched. Two strains fungi (Penicillium K3 and N1) and one strain antagonistic bacteria (Burkholderia J2) were isolated. The in intro test results indicated the bacterial suspension, fermentation broth and volatile organic compounds of antagonistic bacteria J2 were able to significantly inhibit pathogen growth. In vivo experiments, peach was stored at 28 °C for 6 days after different treatments, and samples were taken every day. It was found that Burkholderia J2 enhanced peach resistance by increasing the activities of antioxidant-related enzymes such as SOD, POD, PAL, PPO, GR, MDHAR, and DHAR. The results improved that Burkholderia J2 has great biocontrol potential and could be used as a candidate strain for green control of blue mold.

PeAP1-mediated oxidative stress response plays an important role in the growth and pathogenicity of Penicillium expansum.

Penicillium expansum is the causal agent of post-harvest blue mold in various fruits and serves as a model for understanding fungal pathogenicity and mycotoxin production. The relevance of oxidative stress response in the growth and virulence of P. expansum has been largely unexplored. Here, we identify the transcriptional factor PeAP1 as a regulator of oxidative stress response in P. expansum. Gene expression and protein abundance of PeAP1, as well as its nuclear localization, are specifically induced by H2O2. Deletion of PeAP1 results in increased sensitivity to H2O2, and PeAP1 mutants exhibit a variety of defects in hyphal growth and virulence. PeAP1 prevents the accumulation of both intracellular H2O2 during vegetative growth and host-derived H2O2 during biotrophic growth. Application of an antioxidant glutathione and a NADPH oxidase inhibitor, diphenylene iodonium, to the PeAP1 mutant partially restored fungal growth and virulence. RNA sequencing analysis revealed 144 H2O2-induced PeAP1 target genes, including four antioxidant-related genes, PeGST1, PePrx1, PePrx2, and PeTRX2, that were also demonstrated to be involved in oxidative stress response and/or virulence. Collectively, our results demonstrate the global regulatory role of PeAP1 in response to oxidative stress and provide insights into the critical role of the PeAP1-mediated oxidative stress response to regulate growth and virulence of P. expansum. IMPORTANCE Reactive oxygen species are the core of host plant defense and also play a vital role in the successful invasion of host plants by pathogenic fungi. Despite its importance, the relevance of oxidative stress response in fungal growth and virulence is poorly understood in P. expansum. In this study, we reveal that the transcription factor PeAP1 acts as a central regulator of oxidative stress response in P. expansum and that there is a major link between PeAP1-mediated oxidative stress response and fungal growth and virulence. To explore the underlying mechanisms, we performed comparative transcriptomic studies and identified a number of H2O2-induced PeAP1 target genes, including four novel ones, PePrx1, PePrx2, PeGST1, and PeTRX2, whose functions were linked to PeAP1 and pathogenicity. These findings provide novel insights into the regulation mechanism of PeAP1 on growth and virulence, which might offer promising targets for control of blue mold and patulin contamination.

Genome identification and biocontrol potential against citrus blue mold of Bacillus velezensis w176

Citrus fruit is susceptible to Penicillium mold infection. Biocontrol with utilization of antagonistic microorganisms against postharvest diseases is regarded as an effective and eco-friendly approach in citrus fruit storage. Here, the complete genome of biocontrol strain w176 was obtained with a full length of 3,929,790 bp, and it consists of 12 potential gene clusters which might be responsible for antagonistic metabolites biosynthesis, strain w176 was identified as Bacillus velezensis by genome alignments eventually. Meanwhile, strong restrictions of spore germination rate (SGR) and hyphae elongation were detected when strain w176 was co-incubated with P. italicum, the inhibitory of SGR at 6 h, 9 h and 12 h was 10.00%, 49.59% and 23.53%, respectively. And the inhibitory of hyphae elongation was 35.56% at 12 h. It was also found that strain w176 exhibited notable growth space competition in the co-incubation. Moreover, significantly enhanced activities of catalase and chitinase in citrus fruit were presented 2 d and 3 d post-inoculation with strain w176. Further, citrus fruit treated by strain w176 PDB culture (PBC) or its culture filtrate (CFS) displayed significantly reduced virulence of P. italicum contamination, the decreased disease symptoms of CFS and PBC were 30.32% and 85.22%, individually. The inhibitory disease rate of PBC was 25%. This study reveals that strain w176 has high potential to be applied as bio-pesticide in citrus preservation. The data attained in this research might be helpful for citrus blue mold control, and could provide basis for the bio-preservation study in postharvest fruit.

Efficacy and Mechanisms of Action of Essential Oils' Vapours against Blue Mould on Apples Caused by Penicillium expansum.

Biofumigation with slow-release diffusers of essential oils (EOs) of basil, oregano, savoury, thyme, lemon, and fennel was assessed for the control of blue mould of apples, caused by Penicillium expansum. In vitro, the ability of the six EOs to inhibit the mycelial growth was evaluated at concentrations of 1.0, 0.5, and 0.1%. EOs of thyme, savoury, and oregano, at all three concentrations, and basil, at 1.0 and 0.5%, were effective in inhibiting the mycelial growth of P. expansum. In vivo, disease incidence and severity were evaluated on 'Opal' apples artificially inoculated with the pathogen and treated at concentrations of 1.0% and 0.5% of EOs. The highest efficacy in reducing blue mould was observed with EOs of lemon and oregano at 1.0% after 60 days of storage at 1 ± 1 °C (incidence of rot, 3 and 1%, respectively) and after a further 14 days of shelf-life at 15 ± 1 °C (15 and 17%). Firmness, titratable acidity, and total soluble solids were evaluated at harvest, after cold storage, and after shelf-life. Throughout the storage period, no evident phytotoxic effects were observed. The EOs used were characterised through GC-MS to analyse their compositions. Moreover, the volatile organic compounds (VOCs) present in the cabinets were characterised during storage using the SPME-GC-MS technique. The antifungal effects of EOs were confirmed both in vitro and in vivo and the possible mechanisms of action were hypothesised. High concentrations of antimicrobial and antioxidant compounds in the EOs explain the efficacy of biofumigation in postharvest disease control. These findings provide new insights for the development of sustainable strategies for the management of postharvest diseases and the reduction of fruit losses during storage.

Screening of antagonistic yeast strains for postharvest control of Penicillium expansum causing blue mold decay in table grape

Blue mold decay caused by Penicillium expansum is one of the most important postharvest diseases of grapes, leading to considerable economic losses. Regarding the increasing demand for pesticide-free foods, this study aimed to find potential yeast strains for biological control of blue mold on table grapes. A total of 50 yeast strains were screened for antagonistic activity against P. expansum using the dual culture method and six strains significantly inhibited the fungal growth. All six yeast strains (Coniochaeta euphorbiae, Auerobasidium mangrovei, Tranzscheliella sp., Geotrichum candidum, Basidioascus persicus, and Cryptococcus podzolicus) reduced the fungal growth (29.6–85.0%) and the decay degree of wounded grape berries inoculated with P. expansum while G. candidum was found to be the most efficient biocontrol agent. On the basis of antagonistic activity, the strains were further characterized by in vitro assays involving inhibition of conidial germination, production of volatile compounds, iron competition, production of hydrolytic enzymes, biofilm-forming capacity, and exhibited three or more putative mechanisms. To our knowledge, the yeasts are reported for the first time as potential biocontrol agents against the blue mold of grapes but more study is required to evaluate their efficiency related to field application.

Control Efficacy of Salicylic Acid Microcapsules against Postharvest Blue Mold in Apple Fruit.

Salicylic acid (SA) is a natural inducer of disease resistance in fruit, but its application in the food industry is limited due to low water solubility. Here, SA was encapsulated in β-cyclodextrin (β-CD) via the host-guest inclusion complexation method, and the efficacy of SA microcapsules (SAM) against blue mold caused by Penicillium expansum in postharvest apple fruit was elucidated. It was observed that SAM was the most effective in inhibiting the mycelial growth of P. expansum in vitro. SAM was also superior to SA for control of blue mold under in vivo conditions. Enzyme activity analysis revealed that both SA and SAM enhanced the activities of superoxide dismutase (SOD) and phenylalanine ammonia lyase (PAL) in apple fruit, whereas SAM led to higher SOD activities than SA. Total phenolic contents in the SAM group were higher than those in the SA group at the early stage of storage. SAM also improved fruit quality by retarding firmness loss and maintaining higher total soluble solids (TSS) contents. These findings indicate that microcapsules can serve as a promising formulation to load SA for increasing P. expansum inhibition activity and improving quality attributes in apple fruit.

Comparative proteome and transcriptome analyses of the response of postharvest pears to Penicillium expansum infection

Penicillium expansum causes blue mold disease in pears during storage and transportation, causing huge economic losses. However, researches on the defense mechanisms of pears against P. expansum are still in the early stages. Therefore, many unknown disease-resistant factors have yet to be excavated, severely limiting the breakthrough progress of pear blue mold control strategies. The current study used transcriptome and proteome approaches to evaluate pear defense mechanisms following infection with P. expansum. 96% of pear proteins were associated with the transcriptome data. Gene Ontology (GO) enrichment analysis determined that the remaining associated genes/proteins were significantly enriched in 80 GO terms. The significantly enriched GO terms included oxyacid metabolism, aldehyde-lyase activity, transition metal ion binding, terpenoid metabolic process, response to stimulus, etc. An enrichment analysis conducted by the Kyoto Encyclopedia of Genes and Genomes (KEGG) showed that 122 metabolic pathways were enriched, of which 11 were closely related to other metabolic pathways. In these 11 metabolic pathways, the genes/proteins (such as peroxidase, histidinol-phosphate aminotransferase (hisC), prephenate dehydratase (ADT), etc.) related to the biosynthesis of plant secondary metabolites, and the genes/proteins (such as ethylene-responsive transcription factor 1 (ERF), BR-signaling kinase (BSK), brassinosteroid insensitive 1-associated receptor kinase 1 (BAK1), etc.) related to plant hormones were significantly enriched. Overall, this study provides a deep understanding of pear’s defense response, which could be used in future research to develop strategies to control fungal diseases.

Study on the effect of Debaryomyces hansenii enhanced by alginate oligosaccharide against postharvest blue mold decay of apples and the physiological mechanisms involved

Blue mold decay is the most common disease during postharvest storage of apples caused by Penicillium expansum, leading to huge economic losses to the apple industry. Antagonistic yeasts are widely used in biological control, and organic compounds can be used as elicitors to induce antagonistic yeasts to further improve their biocontrol effect. In this study, we assessed the biocontrol efficacy of the antagonistic yeast, Debaryomyces hansenii, enhanced by alginate oligosaccharide (AOS) in controlling the postharvest decay of apples and studied the possible physiological mechanisms involved in this process. The results of this study were as follows: (1) AOS enhanced the biocontrol ability of D. hansenii against P. expansum infestation of apples. In the in vivo experiments, D. hansenii induced by 0.5% AOS significantly reduced the disease incidence and lesion diameter in apples, demonstrating good control of blue mold. When treated with D. hansenii-induced with AOS, the disease incidence rate of apples was only 21.6%, while that of yeast alone was 37.5%. (2) In the in vitro experiments, AOS significantly improved the inhibitory effect of D. hansenii on the germination rate, germ tube length, and colony diameter of P. expansum. The results suggested that AOS-induced yeast exhibited a certain inhibitory effect on the growth of P. expansum. (3) The activities of diseases resistance-related enzymes of apples treated with AOS-induced D. hansenii such as polyphenol oxidase (PPO), peroxidase (POD), and phenylalanine ammonia-lyase (PAL) were increased compared to the yeast alone and the control group. Apart from that, the content of substances such as total phenols and flavonoids maintained the original level. These results suggest that the resistance of apples against pathogenic fungi may be improved by increasing the activities of disease resistance related enzymes activities of the fruit. In summary, the method of enhancing antagonistic yeast by AOS is very promising and efficient for improving biological control to reduce economic losses in the apple industry.

Blue mold control and volatile compounds in “Fuji” apples treated with chitosan emulsion combined with essential oils

The aim of this work was to evaluate the effects of chitosan emulsion (CE) in combination with essential oils (Eos) on blue mold control, as well as on aroma and quality attributes of “Fuji” apples after storage. Treatments evaluated were control, CE (1%) and CE (1%) combined with citronella, clove and copaiba EOs (all EOs at 500 μl L−1). Fruits treated with EC and EC + OEs showed lower total phenolic compounds in the peel in all treatments. Fruits treated with EC combined with citronella OEs (242.4 OD mg–1 of protein min–1) and clove (205.8 OD mg–1 of protein min–1) showed lower peroxidase activity in fruit peel tissue. Therefore, CE and CE combined with citronella, clove and copaiba essential oils reduced the development of blue mold in “Fuji” apples. In addition, the treatments with lower severity of blue mold showed lower peroxidase activity in the peel and pulp tissues of the fruit, indicating induction of resistance by essential oils. Novelty impact statement Chitosan biofilm reduces rot by P. expansum in “Fuji” apples, and when in addition to chitosan, essential oils of citronella, clove and copaiba are used, there was an increase in the reduction of disease severity. The aroma of the fruit did not present a characteristic aroma of the essential oils used with the method of application used. There were no changes in fruit quality attributes with the use of chitosan and chitosan biofilm with the addition of essential oils.

Global transcriptomic responses orchestrate difenoconazole resistance in Penicillium spp. causing blue mold of stored apple fruit

BackgroundBlue mold is a globally important and economically impactful postharvest disease of apples caused by multiple Penicillium spp. There are currently four postharvest fungicides registered for blue mold control, and some isolates have developed resistance manifesting in decay on fungicide-treated fruit during storage. To date, mechanisms of fungicide resistance have not been explored in this fungus using a transcriptomic approach.ResultsWe have conducted a comparative transcriptomic study by exposing naturally-occurring difenoconazole (DIF) resistant (G10) and sensitive (P11) blue mold isolates to technical grade difenoconazole, an azole fungicide in the commercial postharvest product Academy (Syngenta Crop Protection, LLC). Dynamic changes in gene expression patterns were observed encompassing candidates involved in active efflux and transcriptional regulators between the resistant and sensitive isolates. Unlike other systems, 3 isoforms of cytochrome P450 monoxygenase (CYP51A-C) were discovered and expressed in both sensitive and resistant strains upon difenoconazole treatment. Active efflux pumps were coordinately regulated in the resistant isolate and were shown to mediate the global resistance response as their inhibition reversed the difenoconazole-resistant phenotype in vitro.ConclusionsOur data support the observation that global transcriptional changes modulate difenoconazole resistance in Penicillium spp. While the dogma of CYP51 overexpression is supported in the resistant isolate, our studies shed light on additional new mechanisms of difenoconazole resistance on a global scale in Penicillium spp. These new findings broaden our fundamental understanding of azole fungicide resistance in fungi, which has identified multiple genetic targets, that can be used for the detection, management, and abatement of difenoconazole-resistant blue mold isolates during long-term storage of apples.

Baseline Sensitivity of Penicillium spp. to Difenoconazole.

Penicillium spp. cause blue mold of stored pome fruit. These fungi reduce fruit quality and produce mycotoxins that are regulated for processed fruit products. Control of blue mold is achieved by fungicide application, and in 2015 Academy (active ingredients fludioxonil and difenoconazole) was released for use on pome fruit to manage postharvest blue mold. Baseline sensitivity for fludioxonil but not difenoconazole has been determined for P. expansum. To establish the distribution of sensitivity to difenoconazole before commercial use of Academy, 97 unexposed single-spore isolates from the United States and abroad were tested in vitro. Baseline EC50 values ranged from 0.038 to 0.827 µg/ml of difenoconazole with an average of 0.16 µg/ml. Complete inhibition of mycelial growth for all but three isolates occurred at 5 µg/ml of difenoconazole, whereas 10 µg/ml did not support growth for any of the isolates examined. Hence, 5 µg/ml of difenoconazole is recommended for phenotyping Penicillium spp. isolates with reduced sensitivity. Isolates with resistance to pyrimethanil and to both thiabendazole and pyrimethanil were observed among the isolates from the baseline collection. Academy applied at the labeled rate had both curative and protectant activities and controlled four representative Penicillium spp. from the baseline population. This information can be used to monitor future shifts in sensitivity to this new postharvest fungicide in Penicillium spp. populations.

Essential oils for the postharvest control of blue mold and quality of 'Fuji' apples

Abstract: The objective of this work was to evaluate the effect of rosemary, cinnamon, citronella grass, and clove essential oils on the in vitro growth of Penicillium expansum, on the diameter of blue mold lesions, and on the physical and chemical attributes of 'Fuji' apples stored under refrigeration for different periods of time. The compositions of the essential oils were determined, and their effects on the growth inhibition, number, and viability of fungal spores in vitro were evaluated at 0, 100, and 1,000 μL L-1 oil concentrations. At postharvest, evaluations were performed for fruit treated with 0, 50, 100, and 500 μL L-1 essential oil and kept under refrigeration for 30 days, and for fruit treated with 0, 100, and 500 μL L-1 oil and kept under refrigeration for two days. The essential oils - eucalyptol (rosemary), eugenol (cinnamon), citronellal (citronella), and eugenol (clove) - reduce the growth, number, and viability of P. expansum spores 24 hours after the induction to germination, as well as the diameter of blue mold lesions in apples, except for citronella oil at 500 μL L-1 after 30 days of cold storage. There are no changes in the physicochemical attributes of apples, treated with different concentrations of the oils after refrigeration for five months, followed by seven days at room temperature.

Antifungal activity and action mechanisms of yeasts isolates from citrus against Penicillium italicum

Penicillium italicum (Blue mold) is a major postharvest disease of citrus. An alternative to controlling the disease is through the use of yeasts. The purpose of the present study was to screen effective yeast antagonists against P. italicum, isolated from soil, leaves, flowers, and citrus fruits, to assess the action mechanisms of the yeast isolates that were demonstrated to be effective for biocontrol, and to identify the most effective yeast isolates for the biocontrol of blue mold. The in vitro assays showed that six yeast strains inhibited up to 90% of the pathogen's mycelial growth. In vivo assays, evaluating the incidence of blue mold on sweet oranges, the strains ACBL-04, ACBL-05, ACBL-10 and ACBL-11 were effective, demonstrating the potential for the blue mold control when preventively applied, whereas the ACBL-08 strain showed a high potential to preventive and curative applications. Additional studies on the modes of action of these yeast strains showed that most of the evaluated yeast strains did not produce antifungal substances, in sufficient quantities to inhibit the pathogen growth. Competition for nutrients was not a biocontrol strategy used by the yeast strains. The ‘killer’ activity might be the main action mechanism involved in P. italicum biocontrol. This study indicated that the multiple modes of action against the pathogen presented by yeasts may explain why these strains provided P. italicum control under in vitro and in vivo conditions. However, further studies in future might be able to elucidate the ‘killer’ activity and its interaction with pathogen cells and the bioproduct production using Candida stellimalicola strains for control postharvest diseases.

Autoclaved yeast enhances the resistance against Penicillium expansum in postharvest pear fruit and its possible mechanisms of action

The study investigated the effect of autoclaved yeast on the control of blue mold in pear fruit and the possible mechanisms involved. The results demonstrated that autoclaved yeast Rhodosporidium paludigenum could stimulate remarkable resistance to the blue mold caused by Penicillium expansum in pear fruit. Autoclaved yeast had no direct antifungal activity against P. expansum in vitro and in vivo while it reduced germination of P. expansum in fruit wounds after 24 h of treatment. Moreover, the activities of four defense-related enzymes (including superoxide dismutase, catalase, peroxidase and phenylalanine ammonia-lyase) and the four pathogenesis-related protein genes (including PR1-like, endoglucanase9, endochitinase-like and PR4) were significantly enhanced and the lipid peroxidation was highly inhibited in the treatment with autoclaved yeast, which was closely related to the mechanism by which autoclaved yeast reduce the blue mold rot in pear fruit. The results from this study provides the basis for further research on the antagonistic mechanism of biocontrol yeasts in induced resistance of harvested fruit.

Alternative treatments for postharvest control of blue mold in ‘Fuji’ apples

Alternative treatments for postharvest control of blue mold in ‘Fuji’ apples

Effects of quercetin on postharvest blue mold control in kiwifruit

Abstract The effects of quercetin on inhibiting Penicillium expansum infections of ‘Qinmei’ kiwifruit during postharvest storage were evaluated. Severe damage to P. expansum’s mycelial structure was observed by transmission electron microscope at a quercetin concentration of 0.25 mg/mL. With the quercetin treatment, kiwifruit infected with P. expansum had higher chitinase, β-1,3-glucanase, phenylalanine ammonialyase, polyphenol oxidase and peroxidase activities, as well as nonexpressor of pathogenesis-related gene 1, pathogenesis-related gene 1, chitinase and β-1,3-glucanase expression levels, compared with those of kiwifruit only treated with quercetin or inoculated with P. expansum. Thus, the inhibitory effects of quercetin on the P. expansum blue mold may be associated with its toxic properties against fungal pathogens and inhibition of defense responses.

Postharvest biological control of blue mold of apple by Pseudomonas fluorescens during commercial storage and potential modes of action

Three Pseudomonas fluorescens isolates, 1–112, 2–28 and 4–6, isolated from the rhizosphere of pulse crops were tested for their ability to suppress Penicillium expansum (blue mold) on ‘McIntosh’ and ‘Spartan’ apples in commercial cold storage, and their possible mechanisms of action were investigated in vitro. On ‘McIntosh’ apples the decay incidence and lesion diameter of blue mold were significantly reduced by isolates 1–112 and 4–6 compared with control fruits after 15 weeks storage at 1°C. On ‘Spartan’ apples only isolate 2–28 provided significant levels of disease control after 15 weeks of storage at 1°C. In dual culture and in volatile tests all three isolates of P. fluorescens significantly inhibited conidial germination and mycelial growth of P. expansum in vitro. All three isolates were positive for the production of protease, but negative for cellulase, chitinase and glucanase. Molecular evidence for the potential for synthesis of the antibiotic, phenazine-1-carboxylic acid, in isolates 1–112 and 4–6 and of hydrogen cyanide in isolate 2–28 was obtained by polymerase chain reaction of phzCD and hcnBC genes, respectively. Genes for 2,4-diacetylphloroglucinol, pyoluteorin and pyrrolnitrin production were not detected in any of the P. fluorescens isolates. Scanning electron microscopy indicated that all three P. fluorescens isolates adhered to the fungal hyphae and colonized the wounds of apples, but only isolate 1–112 was able to colonize conidia of the fungal pathogen. P. fluorescens’ ability to compete for nutrients and space and produce inhibitory metabolites that target conidial germination and mycelial growth may be the basis for its control of P. expansum on apple.

Control of blue mould and bitter rot of apples, and brown rot of peaches by Citrus aurantium extract-based product BIOLASTING®

Control of blue mould and bitter rot of apples, and brown rot of peaches by <i>Citrus aurantium</i> extract-based product BIOLASTING^®

Effects of the protective, curative, and eradicative applications of chitosan against Penicillium expansum in apples.

Apple is one of the most important temperate fruit to Brazil economy, and the use of synthetic chemicals has been the main method for reducing postharvest diseases, such as the blue mold, caused by Penicillium expansum. This work intends to evaluate the practical utilization of chitosan for blue mold control. For this purpose, fruits were treated in a preventive and curative way, immersing the fruits in chitosan solution (5 or 10 mg mL−1), or adding a single drop of this solution (10 mg mL−1) directly into the injuries. The eradicative effect of the polysaccharide was also evaluated in vitro and in vivo. Chitosan did not show a curative effect against the blue mold, and its eradicative effect was only evidenced on the higher concentration (10 mg mL−1). On the other hand, preventively, without the addition of adjuvants, chitosan reduced blue mold incidence in fruits by 24% and 93%, through the immersion or the single drop methods, respectively. Thus, it was found that, for long scale utilization, some improvements in the physico-chemical properties of the chitosan are needed, since it was only capable to prevent the infection by P. expansum when directly added on the fruit injury.

Use of active extracts of poplar buds against Penicillium italicum and possible modes of action

Antifungal components, from poplar buds active fraction (PBAF) against Penicillium italicum, the causal agent of blue mold in citrus fruits, were identified and possible action modes were investigated. Pinocembrin, chrysin and galangin were determined as active components in PBAF, using HPLC and HPLC–MS analysis. The antifungal activity is stable at temperatures ranging from 4°C to 100°C and pH levels ranging from 4 to 8. In the presence of PBAF, the hyphae become shriveled, wrinkled and the cell membrane became seriously disrupted. Further investigation on cell permeability, nucleic acid content and alkaline phosphatase suggest that the cell membrane might be the target. Mycelial oxygen consumption and the respiration-related enzymatic activity of succinate dehydrogenase, malate dehydrogenase and ATPase were all inhibited by PBAF. We propose that PBAF is a potentially useful alternative for blue mold control and may act against P. italicum by interfering with respiration and disrupting the cell membrane.