Blue Mold Disease Research Articles

New Trichoderma Strains Suppress Blue Mold in Oranges by Damaging the Cell Membrane of Penicillium italicum and Enhancing Both Enzymatic and Non-Enzymatic Defense Mechanisms in Orange Fruits

Blue mold disease, caused by Penicillium italicum (P. italicum), presents a significant challenge to orange fruits (Citrus sinensis L.) and other citrus crops globally. Biological control, particularly Trichoderma species, offers a promising alternative to synthetic fungicides. Therefore, this study aimed to isolate, identify, and evaluate the antagonistic activities of two Trichoderma isolates against P. italicum. These isolates were molecularly identified and assigned accession numbers PP002254 and PP002272, respectively. Both isolates demonstrated significant antifungal activity in dual culture assays. Moreover, the culture filtrates (CFs) of Trichoderma longibrachiatum PP002254 and Trichoderma harzianum PP002272 suppressed the mycelial growth of P. italicum by 77.22% and 71.66%, respectively. Additionally, CFs reduced the severity of blue mold on orange fruits by 26.85% and 53.81%, compared to 100% in the control group. Scanning electron microscopy revealed that treated P. italicum hyphae were shrunken and disfigured. Enzyme activities (catalase, peroxidase, polyphenol oxidase, and phenylalanine ammonia-lyase) in treated oranges increased, along with total soluble phenolics and flavonoids. Conversely, malondialdehyde (MDA) levels decreased in treated fruits. These findings suggest that T. longibrachiatum PP002254 and T. harzianum PP002272 could be effective biocontrol agents for managing blue mold and other citrus postharvest diseases.

Chromatin accessibility profile and the role of PeAtf1 transcription factor in the postharvest pathogen Penicillium expansum

Abstract Gene transcription is governed by a complex regulatory system involving changes in chromatin structure, action of transcription factors, and activation of cis-regulatory elements. Postharvest fruits are threatened by Penicillium expansum, a leading causal agent of blue mold disease and one of the most economically significant postharvest pathogens worldwide. However, the information on its transcription regulatory mechanism is lagging. Here, we conducted an assay for transposase accessible chromatin sequencing (ATAC-seq) for P. expansum during vegetative growth and infection phase and then studied the function of a bZIP transcription factor PeAtf1. Results highlighted the role of promoter regions in gene transcription and the significant difference in P. expansum between the two phases. Six footprint-supported cis-regulatory elements of active transcription factors were obtained and analyzed. We then identified a homolog of the bZIP regulator Atf1, PeAtf1, and found it positively regulated vegetative growth, reproduction and osmotic stress response in P. expansum. Conversely, PeAtf1 deletion enhanced fungal tolerance to oxidative, cell wall and membrane stresses, which might contribute to the virulence of P. expansum in apple fruits, leading to similar pathogenicity between mutants and the wild type. Overall, this study provides new insights into the transcription regulatory mechanism of P. expansum, aiding in the future development of strategies to control P. expansum.

Nobiletin enhances the antifungal activity of eugenol nanoemulsion against Penicillium italicum in both in vitro and in vivo settings

The study prepared and used eugenol nanoemulsion loaded with nobiletin as fungistat to study its antifungal activity and potential mechanism of Penicillium italicum (P. italicum). The results showed that the minimum inhibitory concentration (MIC) of eugenol nanoemulsion loaded with nobiletin (EGN) was lower than that of pure eugenol nanoemulsion (EG), which were 160 μg/mL and 320 μg/mL, respectively. At the same time, the mycelial growth inhibition rate of EGN nanoemulsion (54.68 %) was also higher than that of EG nanoemulsion (9.92 %). This indicates that EGN nanoemulsion is more effective than EG nanoemulsion. Compared with EG nanoemulsion, the treatment of EGN nanoemulsion caused more serious damage to the cell structure of P. italicum. At the same time, in vitro inoculation experiments found that EGN nanoemulsion has better control and delay the growth and reproduction of P. italicum in citrus fruits. And the results reflected that EGN nanoemulsion may be considered as potential resouces of natural antiseptic to inhibit blue mold disease of citrus fruits, because it has good antifungal activity.

Antagonistic Activities of Metschnikowia pulcherrima Isolates Against Penicillium expansum on Amasya Apples.

Postharvest fungal diseases cause serious fruit losses and food safety issues worldwide. The trend in preventing food loss and waste has shifted to environmentally friendly and sustainable methods, such as biological control. Penicillium expansum is a common postharvest contaminant fungus that causes blue mould disease and patulin formation on apples. This study aimed to provide biocontrol using Metschnikowia pulcherrima isolates against P. expansum, and to understand their antagonistic action mechanisms. In vitro, 38.77-51.69% of mycelial growth inhibition of P. expansum was achieved by M. pulcherrima isolates with the dual culture assay, while this rate was 69.45-84.89% in the disc diffusion assay. The disease symptoms of P. expansum on wounds were reduced by M. pulcherrima, on Amasya apples. The lesion diameter, 41.84mm after 12 d of incubation in control, was measured as 24.14mm when treated with the most effective M. pulcherrima DN-MP in vivo. Although the antagonistic mechanisms of M. pulcherrima isolates were similar, there was a difference between their activities. In general, DN-HS and DN-MP isolates were found to be more effective. In light of all these results, it can be said that M. pulcherrima isolates used in the study have an antagonistic effect against the growth of P. expansum both in vitro and in vivo in Amasya apples, therefore, when the appropriate formulation is provided, they can be used as an alternative biocontrol agent to chemical fungicides in the prevention of postharvest diseases.

Comparative physiological and transcriptomic analysis reveals an improved biological control efficacy of Sporidiobolus pararoseus Y16 enhanced with ascorbic acid against the oxidative stress tolerance caused by Penicillium expansum in pears

Sporidiobolus pararoseus Y16, a species of significant ecological importance, has distinctive physiological and biological regulatory systems that aid in its survival and environmental adaptation. The goal of this investigation was to understand the complex interactions between physiological and molecular mechanisms in pear fruits as induced by S. pararoseus Y16. The study investigated the use of S. pararoseus Y16 and ascorbic acid (VC) in combination in controlling blue mold decay in pears via physiological and transcriptomic approach. The study results showed that treatment of S. pararoseus Y16 with 150 μg/mL VC reduced pears blue mold disease incidence from 43% to 11%. Furthermore, the combination of S. pararoseus Y16 and VC significantly inhibited mycelia growth and spore germination of Penicillium expansum in the pear's wounds. The pre-treatment did not impair post-harvest qualities of pear fruit but increased antioxidant enzyme activity specifically polyphenol oxidase (PPO), peroxidase (POD), catalase (CAT) activities as well as phenylalanine ammonia-lyase (PAL) enzyme activity. The transcriptome analysis further uncovered 395 differentially expressed genes (DEGs) and pathways involved in defense mechanisms and disease resistance. Notable pathways of the DEGs include plant-pathogen interaction, tyrosine metabolism, and hormone signal transduction pathways. The integrative approach with both physiological and transcriptomic tools to investigate postharvest pathology in pear fruits with clarification on how S. pararoseus Y16 enhanced with VC, improved gene expression for disease defense, and create alternative controls strategies for managing postharvest diseases.

The complete mitochondrial genome of Penicillium expansum: Insights into the fungal evolution and phylogeny

Penicillium expansum is an important phytopathogenic fungus that causes blue mold disease. In this study, the novel mitochondrial genome of P. expansum was sequenced, assembled, annotated, and compared with the previously published Penicillium mitogenomes. P. expansum mitogenome is composed of circular DNA molecules with a genome size of 25,496 bp. It encodes 16 protein-encoding genes (PCGs), two rRNA genes, and 25 tRNA genes. Comparative analysis with six other Penicillium species revealed that gene length, GC content, AT skew, and GC skew were variable among the core protein-coding genes. The Penicillium species' gene synteny analysis identified several gene rearrangements. Among the core 15 PCGs, atp8 had the lowest K2P genetic distance, which shows that this gene is highly conserved. The Ka/Ks value of most PCGs was less than 1, which shows that these genes have undergone purifying selection. Phylogenetic analysis based on 14 concatenated core mitochondrial genes revealed that P. expansum shares a close relationship with P. solitum. This study served as a first report on the complete mitochondrial genome of P. expansum and its comparative analysis that will contribute to population genetics and rapid evolutionary studies among Penicillium species.

The Influence of Long-Term Storage on the Epiphytic Microbiome of Postharvest Apples and on Penicillium expansum Occurrence and Patulin Accumulation.

Patulin is a secondary metabolite primarily synthesized by the fungus Penicillium expansum, which is responsible for blue mold disease on apples. The latter are highly susceptible to fungal infection in the postharvest stages. Apples destined to produce compotes are processed throughout the year, which implies that long periods of storage are required under controlled atmospheres. P. expansum is capable of infecting apples throughout the whole process, and patulin can be detected in the end-product. In the present study, 455 apples (organically and conventionally grown), destined to produce compotes, of the variety "Golden Delicious" were sampled at multiple postharvest steps. The apple samples were analyzed for their patulin content and P. expansum was quantified using real-time PCR. The patulin results showed no significant differences between the two cultivation techniques; however, two critical control points were identified: the long-term storage and the deck storage of apples at ambient temperature before transport. Additionally, alterations in the epiphytic microbiota of both fungi and bacteria throughout various steps were investigated through the application of a metabarcoding approach. The alpha and beta diversity analysis highlighted the effect of long-term storage, causing an increase in the bacterial and fungal diversity on apples, and showed significant differences in the microbial communities during the different postharvest steps. The different network analyses demonstrated intra-species relationships. Multiple pairs of fungal and bacterial competitive relationships were observed. Positive interactions were also observed between P. expansum and multiple fungal and bacterial species. These network analyses provide a basis for further fungal and bacterial interaction analyses for fruit disease biocontrol.

Metabolomics approach to understand molecular mechanisms involved in fungal pathogen-citrus pathosystems.

Citrus is a crucial crop with a significant economic impact globally. However, postharvest decay caused by fungal pathogens poses a considerable threat, leading to substantial financial losses. Penicillium digitatum, Penicillium italicum, Geotrichum citri-aurantii and Phyllosticta citricarpa are the main fungal pathogens, causing green mold, blue mold, sour rot and citrus black spot diseases, respectively. The use of chemical fungicides as a control strategy in citrus raises concerns about food and environmental safety. Therefore, understanding the molecular basis of host-pathogen interactions is essential to find safer alternatives. This review highlights the potential of the metabolomics approach in the search for bioactive compounds involved in the pathogen-citrus interaction, and how the integration of metabolomics and genomics contributes to the understanding of secondary metabolites associated with fungal virulence and the fungal infection mechanisms. Our goal is to provide a pipeline combining metabolomics and genomics that can effectively guide researchers to perform studies aiming to contribute to the understanding of the fundamental chemical and biochemical aspects of pathogen-host interactions, in order to effectively develop new alternatives for fungal diseases in citrus cultivation. We intend to inspire the scientific community to question unexplored biological systems, and to employ diverse analytical approaches and metabolomics techniques to address outstanding questions about the non-studied pathosystems from a chemical biology perspective.

Genetic identification, pathogenicity and patulin production of Penicillium species from apple blue mold in China

Abstract Objectives Blue mold is a common postharvest disease that leads to severe rot and patulin (PAT) contamination in fruits, which is a key factor endangering the storage and quality of apple products. However, the Penicillium species from apple blue mold in China and their pathogenicity and PAT production ability have not been well studied. Materials and Methods In this study, 62 strains of pathogenic Penicillium species were isolated from blue mold apples collected from different regions of China. The ITS, BenA, and CaM genes were sequenced for molecular identification. Results Penicillium strains were identified as three species, 57 P. expansum, 3 P. crustosum, and 2 P. polonicum. Twelve variants of the ITS sequence, 61 variants of BenA and 67 variants of CiaM genes were identified between Penicillium species. Fungal morphology was observed on potato dextrose agar (PDA). After 10 d of cultivation, P. expansum cultures were detected with PAT concentrations ranging from 457.98 to 1333.85 mg/kg, and two P. polonicum strains were 6.02 mg/kg and 6.30 mg/kg. The three P. crustosum strains could not produce PAT on PDA. In apple inoculation, P. expansum strains showed significantly faster infection rates than P. crustosum and P. polonicum strains. All P. expansum strains can produce PAT during infection, and the concentrations in the rot apple tissues were 2.31–88.67 mg/kg. The P. crustosum and P. polonicum strains could not produce PAT during infection. Conclusions This study provides data and information regarding the morphology, virulence and PAT production of Penicillium pathogens that will improve the understanding of apple blue mold and postharvest disease control.

Comparative physiological and transcriptome analysis provide insights into the inhibitory effect of osthole on Penicillium choerospondiatis

Blue mold induced by Penicillium choerospondiatis is a primary cause of growth and postharvest losses in the fruit of Phyllanthus emblica. There is an urgent need to explore novel and safe fungicides to control this disease. Here, we demonstrated osthole, a natural coumarin compound isolated from Cnidium monnieri, exhibited a strong inhibitory effect on mycelia growth, conidial germination rate and germ tube length of P. choerospondiatis, and effectively suppressed the blue mold development in postharvest fruit of P. emblica. The median effective concentration of osthole was 9.86 mg/L. Osthole treatment resulted in cellular structural disruption, reactive oxygen species (ROS) accumulation, and induced autophagic vacuoles containing cytoplasmic components in fungal cells. Transcriptome analysis revealed that osthole treatment led to the differentially expressed genes mainly enriched in the cell wall synthesis, TCA cycle, glycolysis/ gluconeogenesis, oxidative phosphorylation. Moreover, osthole treatment led to increase genes expression involved in peroxisome, autophagy and endocytosis. Particularly, the autophagy pathway related genes (PcATG1, PcATG3, PcATG15, PcATG27, PcYPT7 and PcSEC18) were prominently up-regulated by osthole. Summarily, these results revealed the potential antifungal mechanism of osthole against P. choerospondiatis. Osthole has potentials to develop as a natural antifungal agent for controlling blue mold disease in postharvest fruits.

Infection of postharvest pear by Penicillium expansum is facilitated by the glycoside hydrolase (eglB) gene

The primary reason for postharvest loss is blue mold disease which is mainly caused by Penicillium expansum. Strategies for disease control greatly depend on the understanding of mechanisms of pathogen-fruit interaction. A member of the glycoside hydrolase family, β-glucosidase 1b (eglB), in P. expansum was significantly upregulated during postharvest pear infection. Glycoside hydrolases are a large group of enzymes that can degrade plant cell wall polymers. High homology was found between the glycoside hydrolase superfamily in P. expansum. Functional characterization and analysis of eglB were performed via gene knockout and complementation analysis. Although eglB deletion had no notable effect on P. expansum colony shape or microscopic morphology, it did reduce the production of fungal hyphae, thereby reducing P. expansum's sporulation and patulin (PAT) accumulation. Moreover, the deletion of eglB (ΔeglB) reduced P. expansum pathogenicity in pears. The growth, conidia production, PAT accumulation, and pathogenicity abilities of ΔeglB were restored to that of wild-type P. expansum by complementation of eglB (ΔeglB-C). These findings indicate that eglB contributes to P. expansum's development and pathogenicity. This research is a contribution to the identification of key effectors of fungal pathogenicity for use as targets in fruit safety strategies.

The Identification and Comparative Analysis of Non-Coding RNAs in Spores and Mycelia of Penicillium expansum.

Penicillium expansum is the most popular post-harvest pathogen and causes blue mold disease in pome fruit and leads to significant economic losses worldwide every year. However, the fundamental regulation mechanisms of growth in P. expansum are unclear. Recently, non-coding RNAs (ncRNAs) have attracted more attention due to critical roles in normalizing gene expression and maintaining cellular genotypes in organisms. However, the research related to ncRNAs in P. expansum have not been reported. Therefore, to provide an overview of ncRNAs on composition, distribution, expression changes, and potential targets in the growth process, a comparative transcriptomic analysis was performed on spores and mycelia of P. expansum in the present study. A total of 2595 novel mRNAs, 3362 long non-coding RNAs (lncRNAs), 10 novel microRNAs (miRNAs), 86 novel small interfering RNAs (siRNAs), and 11,238 circular RNAs (circRNAs) were predicted and quantified. Of these, 1482 novel mRNAs, 5987 known mRNAs, 2047 lncRNAs, 40 miRNAs, 38 novel siRNAs, and 9235 circRNAs were differentially expressed (DE) in response to the different development stages. Afterward, the involved functions and pathways of DE RNAs were revealed via Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) database enrichment analysis. The interaction networks between mRNAs, lncRNAs, and miRNAs were also predicted based on their correlation coefficient of expression profiles. Among them, it was found that miR168 family members may play important roles in fungal growth due to their central location in the network. These findings will contribute to a better understanding on regulation machinery at the RNA level on fungal growth and provide a theoretical basis to develop novel control strategies against P. expansum.

Set1/COMPASS regulates growth, pathogenicity, and patulin biosynthesis of Penicillium expansum via H3K4 methylation and the interaction with PeVelB

IntroductionPenicillium expansum is a harmful plant fungal pathogen that causes blue mold disease and produces mycotoxin patulin, leading to huge economic losses and food safety hazard. Set1 associated complex Set1/COMPASS deposits the methylation at lysine 4 of histone H3, which is associated with gene expression in diverse biological processes of fungi. However, the function and underlying mechanisms of Set1/COMPASS are poorly defined in P. expansum. ObjectivesThe study aimed to identify Set1/COMPASS and investigate its regulation mechanisms on growth, pathogenicity, and patulin biosynthesis of P. expansum. MethodsAnalyses of phylogenetic relationship, conserved structural domain, and gene deletion were used to identify components of Set1/COMPASS. Phenotype analysis and stress tolerance test of gene deletion mutants were conducted to analyze the function of these components. Yeast two-hybrid, Co-Immunoprecipitation (Co-IP), and point mutation were performed to verify the protein interaction. Western blot was conducted for detection of H3K4 methylation levels. ResultsP. expansum owns six components of Set1/COMPASS besides PeSet1. Absence of each component resulted in reduction of H3K4 methylation levels and impaired growth, pathogenicity, and patulin biosynthesis, as well as altered stress responses of P. expansum. One component PeBre2p was found to interact with the conserved global regulator PeVelB (VelvetLike protein B) at Asp294 of PeBre2p. This interaction affected fungal growth and utilization of fructose, lactose, glycine, and proline in P. expansum. ConclusionThis study revealed the important roles of Set1/COMPASS in P. expansum and clarified for the first time the combined regulation of PeBre2p and PeVelB in fungal growth and nutrition utilization. These results will provide potential targets for the control of blue mold disease.

Endophytic Bacillus atrophaeus CHGP13 and salicylic acid inhibit blue mold of lemon by regulating defense enzymes.

Lemons (Citrus limon L.) are one of the most economically important and consumed fruit worldwide. The species is vulnerable to several postharvest decay pathogens, of which Penicillium italicum associated with blue mold disease is the most damaging. This study investigates the use of integrated management for blue mold of lemon using lipopeptides (LPs) extracted from endophytic Bacillus strains and resistance inducers. Two resistance inducers; salicylic acid (SA) and benzoic acid (BA) were tested at 2, 3, 4, and 5 mM concentrations against the development of blue mold on lemon fruit. The 5 mM SA treatment produced the lowest disease incidence (60%) and lesion diameter (1.4 cm) of blue mold on lemon fruit relative to the control. In an in vitro antagonism assay eighteen Bacillus strains were evaluated for their direct antifungal effect against P. italicum; CHGP13 and CHGP17 had the greatest inhibition zones of 2.30 and 2.14 cm. Lipopeptides (LPs) extracted from CHGP13 and CHGP17 also inhibited the colony growth of P. italicum. LPs extracted from CHGP13 and 5 mM SA were tested as single and combined treatments against disease incidence and lesion diameter of blue mold on lemon fruit. SA + CHGP13 + PI had the lowest disease incidence (30%) and lesion diameter (0.4 cm) of P. italicum on lemon fruit relative to the other treatments. Furthermore, the lemon fruit treated with SA + CHGP13 + PI had the highest PPO, POD, and PAL activities. The postharvest quality analysis of the lemon fruit including fruit firmness, total soluble solids, weight loss, titratable acidity, and ascorbic acid content revealed that the treatment SA + CHGP13 + PI had little effect on fruit quality compared to the healthy control. These findings indicate that Bacillus strains and resistance inducers can be used as components of integrated disease management for the blue mold of lemon.

Antifungal potential of aqueous extracts of coconut (Cocos nucifera L.) by-products against blue mold disease on Persian lime during storage

Antifungal potential of aqueous extracts of coconut (Cocos nucifera L.) by-products against blue mold disease on Persian lime during storage

Aggressiveness and Patulin Production in Penicillium expansum Multidrug Resistant Strains with Different Expression Levels of MFS and ABC Transporters, in the Presence or Absence of Fludioxonil.

Penicillium expansum is the most common postharvest pathogen of apple fruit, causing blue mold disease. Due to the extensive use of fungicides, strains resistant to multiple chemical classes have been selected. A previous study by our group proposed that the overexpression of MFS (major facilitator superfamily) and ABC (ATP binding cassette) transporters constitute an alternative resistance mechanism in Multi Drug resistant (MDR) strains of this pathogen. This study was initiated to determine two main biological fitness parameters of MDR strains: aggressiveness against apple fruit and patulin production. In addition, the expression pattern of efflux transporters and hydroxylase-encoding genes that belong to the patulin biosynthesis pathway, in the presence or absence of fludioxonil and under in vitro and in vivo conditions were investigated. Results showed that the MDR strains produced higher concentrations of patulin but showed a lower pathogenicity compared to the wild-type isolates. Moreover, expression analysis of patC, patM and patH genes indicated that the higher expression levels do not correlate with the detected patulin concentration. The selection of MDR strains in P. expansum populations and the fact that they produce more patulin, constitutes a serious concern not only for successful disease control but also for human health. The above-mentioned data represent the first report of MDR in P. expansum associated with its patulin-production ability and the expression level of patulin biosynthesis pathway genes.

Application of bioactive chitosan-based coatings with marine antagonists to control postharvest Persian lime decay caused by Penicillium italicum

ABSTRACT A novel edible coating with marine yeast in chitosan matrix was prepared. The biocompatibility of yeast cell incorporation of developed coatings was evaluated in terms of viability. Furthermore, the application of chitosan-based coatings was investigated in order to evaluate their efficacy to preserve postharvest quality and prevent fungal establishment of Penicillium italicum during storage under refrigeration. Results revealed that commercial chitosan as a matrix is compatible with Debaryomyces hansenii by maintaining 100% viability of the initial inoculum using chitosan at 0.5%. Preventive application of chitosan combined with the antagonistic yeast was more effective for controlling fungus infection than individual treatments of chitosan and yeast, showing an additive effect. Chitosan concentration had an impact on pH, TSS, acidity, and colour values. Further, the addition of yeast improved the barrier properties of coatings. This study demonstrates the potential application of chitosan-based coatings with antagonistic yeast D. hansenii for Persian lime quality maintenance as well as an effective alternative against blue mould disease.

Isolation of Main Pathogens Causing Postharvest Disease in Fresh Codonopsis pilosula during Different Storage Stages and Ozone Control against Disease and Mycotoxin Accumulation

Codonopsis pilosula is an important Chinese herbal medicine. However, fresh C. pilosula is prone to decay during storage due to microorganism infections, seriously affecting the medicinal value and even causing mycotoxin accumulation. Therefore, it is necessary to study the pathogens present and develop efficient control strategies to mitigate their detrimental effects on the herbs during storage. In this study, fresh C. pilosula was collected from Min County in Gansu Province, China. The natural disease symptoms were observed during different storage stages, and the pathogens causing C. pilosula postharvest decay were isolated from the infected fresh C. pilosula. Morphological and molecular identification were performed, and pathogenicity was tested using Koch's postulates. In addition, the control of ozone was examined against the isolates and mycotoxin accumulation. The results indicated that the naturally occurring symptom increased progressively with the extension of storage time. The mucor rot caused by Mucor was first observed on day 7, followed by root rot caused by Fusarium on day 14. Blue mold disease caused by Penicillum expansum was detected as the most serious postharvest disease on day 28. Pink rot disease caused by Trichothecium roseum was observed on day 56. Moreover, ozone treatment significantly decreased the development of postharvest disease and inhibited the accumulations of patulin, deoxynivalenol, 15-Acetyl-deoxynivalenol, and HT-2 toxin.

Histone H3K4 Methyltransferase PeSet1 Regulates Colonization, Patulin Biosynthesis, and Stress Responses of Penicillium expansum.

Fruit blue mold disease and patulin contamination caused by Penicillium expansum lead to huge economic losses and food safety concerns worldwide. Many genes have been proven to be involved in the regulation of pathogenic and toxigenic processes of P. expansum. Histone H3 lysine 4 (H3K4) methylation is well recognized for its association with chromatin regulation and gene transcription. However, it is not clear whether H3K4 methylation is related to infection and patulin biosynthesis in Penicillium. Here, we characterized PeSet1, which is responsible for H3K4me1/me2/me3 in P. expansum. The deletion of PeSet1 caused severe defects in hyphal growth, conidiation, colonization, patulin biosynthesis, and stress responses. Moreover, we demonstrated that PeSet1 is involved in the regulation of patulin biosynthesis by mediating the expression of patulin cluster genes and crucial global regulatory factors. Likewise, PeSet1 positively regulated key genes in β-1,3-glucan biosynthesis and the reactive oxygen species scavenging process to modulate cell wall integrity and oxidative stress responses, respectively. Collectively, we have proven for the first time the function of Set1 in patulin biosynthesis and the crucial role of Set1 in colonization and stress responses in P. expansum. IMPORTANCE Penicillium expansum is one of the most important plant fungal pathogens, which not only causes blue mold rot in various fruits, leading to huge decay losses, but also produces mycotoxin patulin, posing a threat to human health. Both pathogenesis and patulin biosynthesis in P. expansum are regulated by complex and sophisticated networks. We focused on the epigenetic modification and identified a conserved histone H3K4 methyltransferase PeSet1 in P. expansum. Our work revealed the important role of PeSet1 in growth, development, colonization, patulin production, and stress responses of P. expansum. In particular, we originally described the regulation of Set1 on patulin biosynthetic pathway. These findings will provide new targets for the prevention and control of blue mold disease and patulin contamination.

Antagonistic Potential of Bacillus Strain against the Post-Harvest Blue Mold of Lemon

The present study focuses on the reduction of significant postharvest blue mold disease of lemon (Citrus limon L) fruit through the use of Bacillus strains in vivo and in vitro conditions. Blue mold which is caused by Penicillium italicum is the most dangerous postharvest disease of lemon fruit and causes significant losses in citrus fruits. In this study, antagonistic compounds like Cyclic lipopeptides (CLPs) produced by Bacillus strains were used to control P. italicum. CLPs are considered best the antagonistic compound of Bacillus Strains that primarily play an important role in the reduction of plant diseases and have three important families such as iturin, fengycin, and surfactin. This study was carried out by using seven strains of the genus Bacillus that were used in vitro assay. Among these seven strains, two strains Bacillus licheniformis and Bacillus thuringiensis showed wonderful inhibition zone in vitro assay carried out in Petri plates. Further CLPs were extracted from the both best strains and used in vivo assay on lemon fruit and showed less disease incidence and lesion diameter of disease. Furthermore, lemon fruits treated with CLPs showed increasing defense mechanisms of enzymes P AL, PPO, and PO. This study indicates the strong antifungal effect of Bacillus strains and their metabolites CLPs against the blue mold of lemon.