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Background Chlorophyll is a very important pigment involved in photosynthesis, while plant acyl-CoA biosynthesis is derived from plastid-localized fatty acids (FAs). Until now, the regulation of the acyl-CoA pathway for chlorophyll biosynthesis is still unknown. Results Here, we identified a long-chain acyl-CoA synthetase (LACS) gene BnLACS9 from Brassica napus. BnLACS9 complemented a LACS-deficient yeast strain YB525, which indicated that BnLACS9 has the LACS function. BnLACS9 was localized in the chloroplast envelope membrane, while mainly expressed in young leaves and flowers. Overexpression of BnLACS9 in Nicotiana benthamiana resulted in an increase in total CoA and MGDG content. In B. napus with overexpression of BnLACS9, the number of chloroplast grana lamellae and the chlorophyll content, as well as the MGDG and DGDG contents, increased compared to wild type. The net photosynthetic rate, dry weight of the entire plant and oil content of seeds increased significantly, accompanied by an increase in chlorophyll content. Transcriptome analysis revealed that overexpression of BnLACS9 improved the pathway of acyl-CoA biosynthesis and further improved the enzymes in the glycolipid synthesis pathway, while acyl-CoA was the substrate for glycolipid synthesis. The increased glycolipids, especially MGDG and DGDG, accelerated the formation of the chloroplast grana lamellae, which increased the number of chloroplast thylakoid grana lamella and further lead to increased chlorophyll content. Conclusions In the present study, we demonstrated that BnLACS9 played a crucial role in glycolipids and chlorophyll biosynthesis in B. napus. The results also provide a new direction and theoretical basis for the improvement of the agronomic traits of plants.

In this study, twenty-two baby foods including cereal-based products and powdered infant formula (PIF) obtained from local markets were comprehensively investigated for their bacterial contamination using culture-dependent and high-throughput sequence (HTS) methods. In addition, the genetic diversity and biofilm-forming capacity of the most abundant species were analyzed using random amplified polymorphic DNA (RAPD) and crystal violet staining assay, respectively. Results showed that 170 mesophilic isolates collected from 22 samples were clustered into 15 genera and 41 species. Bacillus (77.65%) was the most prevalent genus, followed by Paenibacillus (7.06%), Alkalibacillus (3.53%), and Lysinibacillus (2.35%). Bacillus licheniformis (49.41%) proved to be the most dominant species in infant foods, and a high genetic diversity with six different RAPD profiles was observed. A total of 87.5% of B. licheniformis isolates were identified as strong biofilm formers, and heterogeneous biofilm-forming ability was observed among the isolates sharing the same RAPD pattern. HTS analysis revealed an 18-fold higher biodiversity at the genus level, and a significantly different bacterial community of infant foods was dominated by Lactococcus, Streptococcus, and Bifidobacterium. Foodborne pathogens including Bacillus cereus, and potentially pathogenic microorganisms such as Acinetobacter baumannii, were identified in infant foods by HTS. The current results could expand the crucial information about bacterial contamination of baby foods.

Patulin contamination not only is a menace to human health but also causes serious environmental problems worldwide due to the synthetic fungicides that are used to control it. This study focused on investigating the patulin degradation mechanism in Pichia caribbica at the molecular level. According to the results, P. caribbica (2 × 106 cells/mL) was able to degrade patulin from 20 μg/mL to an undetectable level in 72 h. The RNA-seq data showed patulin-induced oxidative stress and responses in P. caribbica. The deletion of PcCRG1 led to a significant decrease in patulin degradation by P. caribbica, whereas the overexpression of PcCRG1 accelerated the degradation of patulin. The study identified that PcCRG1 protein had the ability to degrade patulin in vitro. Overall, we demonstrated that the patulin degradation process in P. caribbica was more than one way; PcCRG1 was an S-adenosylmethionine-dependent methyltransferase and played an important role in the patulin degradation process in P. caribbica.

Citrinin (CIT) contamination has been reported in agricultural foods and is known to be nephrotoxic to human and animals. In the present study, the proteomes and transcriptomes of C. podzolicus Y3 treated with or without 10 μg/mL CIT were compared by two-dimensional electrophoresis (2-DE) and RNA sequencing, respectively. The proteomics results showed that there were 23 differentially expressed proteins (DEPs), 8 DEPs were up-regulated and 15 DEPs were significantly down-regulated. Transcriptomic analysis showed that 1208 genes were differentially expressed, 551 (43.05%) DEGs were up regulated and 657 (56.95%) were down-regulated. These results showed that the CIT treatment caused DNA damage, oxidative stress and cell apoptosis in C. podzolicus Y3. CIT treatment also activated the defense response (DNA repair and drug resistance biological process, antioxidative activity and TCA cycle) as well as drug metabolism (synthesize the CIT-degrading enzymes) in yeast cells to respond to CIT stress and degrade CIT.

Talaromyces rugulosus O1 is an ochratoxin A (OTA)-producing pathogen from grapes. The mechanisms involved in the infection of postharvest grapes by T. rugulosus O1 are not yet clear. In this study, the infection of grapes by T. rugulosus O1 and OTA production in grapes were investigated, and the role of cell wall degrading enzymes of T. rugulosus O1 and OTA in the infection of grapes by T. rugulosus O1 was explored. The results indicated that T. rugulosus O1 showed significant infection effect on grapes at 20 °C, and accumulated OTA in the wound of grapes in the infection progress. In comparison with the control, the activities of polygalacturonase (PG), pectin methylgalacturonase (PMG), exo-1,4-β-glucanase (C1) and β-glucosidase (β-G) secreted by T. rugulosus O1 in grapes were all increased in the infection process. Furthermore, the pectinase (PG and PMG) activities were higher than cellulase (C1 and β-G) activities. The expression levels of genes encoding PG and β-G in T. rugulosus O1 infecting grapes increased as the time prolong. Inoculation of T. rugulosus O1 in combination with addition of OTA in the wound of grapes resulted in higher decay incidence and lesion diameter of treated grapes compared with the treatment with T. rugulosus O1 or OTA alone. This indicated that OTA can promote the infection of grapes by T. rugulosus O1. This study provides useful information about the role of cell wall degrading enzymes and OTA in the infection of grapes by T. rugulosus O1.

Increasing patulin contamination in fruits and fruit-derived products has become a major challenge for the food industry. Biological methods of patulin control have an important role to play owing to their safety and efficiency. In this study, we used the yeast Pichia caribbica to degrade patulin effectively. The intermediate degradation products of patulin by P. caribbica were identified as (E)- and (Z)-ascladiol using high performance liquid chromatography and liquid chromatography-tandem mass spectroscopy. Only (E)-ascladiol was detected in the products of patulin degradation by intracellular enzymes. Toxic analyses on Escherichia coli Top10 cells, Arabidopsis thaliana, and human esophageal epithelial cells (Het-1a) showed that the intermediate degradation product ascladiol and the final degradation products were significantly less toxic and almost non-toxic compared to patulin (p 0.05) compared to patulin. Analysis of the characteristics and toxicity of the degradation products of patulin by P. caribbica demonstrate that ascladiol is less toxic and the final degradation products are not poisonous, therefore patulin detoxification strategies using P. caribbica are good approaches to limit the patulin risks.

Meyerozyma guilliermondii significantly inhibited natural decay of stored pears without adverse effects on storage qualities and induced resistance of pears. It was noticed that M. guilliermondii had a significant effect on the induction of several defense-related genes compared to the control, such as genes coding for phenylalanine ammonia lyase (PAL), peroxidase(POD)and β-1, 3 glucannase (GLU). Furthermore, the expression level of GLU in pears treated with M. guilliermondii increased 105-fold compared to the control at 0 d. These findings indicated that M. guilliermondii enhanced the defense-related mechanism of pears. The transcriptome of pears treated with M. guilliermondii and the control were explored after 3 days, the result showed that 144 genes (Log2 fold change ≥ 2, FDR ＜ 0.05) were significantly up-regulated by the induction of M. guilliermondii, some of which include genes of defense-related enzymes such as G-protein coupled receptor 1-like, cationic peroxidase 1-like and beta-glucosidase 12-like were induced corresponding to PAL, POD and GLU respectively. Defense-related transcription factors such as WRKY9, WRKY31 and some other pathogenesis-related genes like Major allergen Pyr c 1, major allergen Pru ar 1-like and major allergen Pru av 1-like were also induced. These results provided a new insight into the biocontrol mechanism of the antagonist yeast in pears.

This study assessed the biocontrol efficacy of Meyerozyma guilliermondii against blue mold decay caused by Penicillium expansum in pears and the possible mechanisms involved. The results indicated that M. guilliermondii significantly inhibited the blue mold decay caused by P. expansum without affecting the quality of the pears. M. guilliermondii rapidly colonized the wounds and surfaces of the pears at both 4 °C and 20 °C. The rapid growth in the population of M. guilliermondii in the wounds and surface environments of pears indicated that it has the potential to inhibit pathogens in pears. The activities of antioxidant enzymes (peroxidase and catalase) in the pear were improved after the application of the yeast. Phenylalanine ammonialyase (PAL), a key enzyme involved in lignin biosynthesis and defense related activity, was also markedly enhanced. Generally, the application of yeast induced disease resistance in the pear. The results pear proteomics profile after M. guilliermondii treatment showed that 17 proteins were significantly up-regulated and 13 were down-regulated in response to induction with M. guilliermondii. Most of the proteins were involved in defense and stress responses based on biological process. These results provided a new insight into the biocontrol mechanism of the antagonist yeast in the pear fruit.

In this study, the activitiesof defense-related enzymes andthose involved in reactive oxygen species (ROS) and their corresponding genes coding for PPO , APX , CHI , PAL and CAT in response to Hanseniaspora uvarum and Hanseniaspora uvarum harvested from NYDB supplemented with 2% w/v trehalose in nutrient yeast dextrose broth (NYDB) were investigated. Conventional methods and qRT-PCR were used to perform defense-related enzyme activities and relative genes expression respectively. The results indicated that H. uvarum enhanced with 2% w/v trehalose demonstrated biocontrol efficacy against Aspergillus tubingensis in grapes.Furthermore, it was noticed that H. uvarum supplemented with 2% w/v trehalose in NYDB had a significantly effect on the induction of defense-related genes expression andenzyme activities compared to the control, 2% w/v trehalose and H. uvarum after storage at 20 °C for 72 h. CAT relative gene expression level in grapes treated with H. uvarum supplemented with 2% w/v trehalose was the highest with 23-fold increase compared to the control. These results suggested that H. uvarum pretreated with trehalose up-regulatedthe defense-relatedgenes expression and enzyme activitiesin the grapes. These findings indicated that, the application of H. uvarum harvested from NYDB supplemented with 2% w/v trehalose enhanced the defense-related mechanism of grapes against A. tubingensis .

Fruits are vulnerable to pathogen infection caused by decay during growth and storage, which causes huge economic losses. The aim of this study was to investigate the biocontrol efficacy of the antagonistic yeast Sporidiobolus pararoseus Y16 in the control of Aspergillus niger decay, and natural decay of table grapes and the possible mechanisms involved. The results showed that S. pararoseus Y16 at different concentrations significantly inhibited A. niger decay of table grapes compared with the control. Besides, the population dynamics results showed that S. pararoseus Y16 could rapidly survive and proliferate in grape wounds or on grape surfaces at 20 °C. Moreover, S. pararoseus Y16 treatment did not impair postharvest qualities of table grapes. Results also showed that treatment with S. pararoseus Y16 enhanced the enzyme activities of polyphenol oxidase (PPO), catalase (CAT), phenylalanine ammonia-lyase (PAL) and ascorbate peroxidase (APX) in table grapes. Furthermore, the gene expression levels of PPO, CAT, PAL and APX were increased by gene level verification. All these results indicated that S. pararoseus Y16 has great potential for development of commercial formulations to control postharvest pathogens on table grapes. These findings revealed that the enhanced gene expression and enzyme activities are the mechanisms involved in the biocontrol, while the yeast outcompeted the fungus for space and nutrients.

Biological control of pathogens using biocontrol agents has been document to be an effective and safe method for managing postharvest diseases. A better understanding of the mode of action of postharvest biocontrol agents on fruit surfaces, is critical for the advancement of successful implementation of postharvest biocontrol products. We investigated the biocontrol efficacy of Yarrowia lipolytica against the postharvest decay of table grapes caused by Talaromyces rugulosus and the possible mechanisms involved. Y. lipolytica significantly decreased the decay incidence of the treated grape berries compared to the untreated control. The response of T. rugulosus to different components of Y. lipolytica indicated that only the yeast cells exhibited inhibitory effect on fungal mycelium, while extracellular metabolites did not show any significant effect on T. rugulosus. The in vitro experiment showed that Y. lipolytica significantly inhibited spores germination and lesion diameter caused by T. rugulosus. We observed that the grape wounds were rapidly colonized by the antagonistic yeast at 25 °C and 4 °C. Thirty-five differential proteins were identified in T. rugulosus out of which 31 were down-regulated. Majority of the down-regulated proteins were related to basic metabolism, which suggested that the basic metabolism of T. rugulosus was suppressed.

Patulin contamination not only is a menace to human health but also causes serious environmental problems worldwide due to the synthetic fungicides that are used to control it. This study focused on investigating the patulin degradation mechanism in

Blue mold, caused by Penicillium expansum, is an important postharvest disease of apple, and can result in significant economic losses. The present study investigated the interaction between P. expansum and wounded apple fruit tissues during the early stages of the infection. Spores of P. expansum became activated one hour post-inoculation (hpi), exhibited swelling at 3 hpi, and the germ tubes were found entering into apple tissues at 6 hpi. RNA-seq was performed on samples of P. expansum and apple fruit tissue collected at 1, 3, and 6 hpi. The main differentially expressed genes (DEGs) that were identified in P. expansum were related to interaction, cell wall degradation enzymes, anti-oxidative stress, pH regulation, and effectors. Apple tissues responded to the presence of P. expansum by activating pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI) at 1 hpi, then activated effector-triggered immunity (ETI) at 3 hpi. This research provides new information on the interaction between P. expansum and apple fruit tissue at an early stage of the infection process.

Losses of harvested fruits and vegetables can be attributed to decaying fungi. These fungi are pathogenic and also a source of mycotoxins, which pose a health threat to humans and animals. As a result, national and international organizations have set detection levels for toxic secondary metabolites for harvested commodities and derived products. Citrinin (CIT) is a mycotoxin produced by fungi and is found in association with patulin, and ochratoxin A, which is nephrotoxic, hepatotoxic, immunosuppression, and carcinogenic. CIT has been recovered from fruit, grains, feedstuff, and biological fluids. Heart, kidney, liver, and reproductive system disorders can be a result of exposure to these mycotoxins. The review points out that, although CIT has health implications, its maximum levels have not been set and not been enforced by national and international organizations. The aim of this review is to look at its occurrence, risks implications, analytical techniques for its detection and quantification, production, biosynthesis, physiochemical properties, and control.

Ochratoxin A (OTA) has been found in a wide range of commodities and is highly toxic to both humans and animals. Therefore, a good understanding of the mechanisms of OTA production by fungi will contribute to the development of eco-friendly methods to mitigate this toxin. In this study, the results showed that Penicillium citrinum X9-4, which was isolated from infected grapes in our laboratory, produced the highest amount of OTA at pH 5 in culture media, and toxin production was restrained under an acidic environment (pH 3). Then, differentially expressed proteins of P. citrinum X9-4 cultured under these two conditions were analyzed by proteomic technology. Additionally, through the analysis of the transcriptome data of P. citrinum cultured at pH 3 and 5, the differentially expressed genes have been found to be involved in many metabolic pathways including amino acid transport and metabolism, transport and metabolism of carbohydrates, inorganic ion transport and metabolism, biosynthesis of secondary metabolites, and energy and supply metabolism, which are likely to be involved in the regulation of OTA biosynthesis. It was also revealed that the expression levels of some OTA synthesis-related enzymes, such as acetyltransferase, acyl coenzyme A oxidase, alcohol oxidase, cytochrome P450, acetyl xylan esterase, and turn ketol enzyme, and genes for the regulation of toxin synthesis pathways were reduced under acidic culture conditions.

The proteomic and lysine acetylation (Kac) changes, accompanying degradation of patulin in Rhodotorula mucilaginosa were analyzed using tandem mass tagging and N6-acetyllysine affinity enrichment followed by LC-MS/MS. Proteomic results showed that expression level of short-chain reductase protein and glutathione S-transferase involved in detoxification was significantly up-regulated. In addition, the expression levels of zinc-binding oxidoreductase and quinone oxidoreductase that are involved in antioxidant process, ABC transport and MFS transport responsible for chemical transport were activated when treated with patulin. The quantitative real time PCR (qRT-PCR) result also indicated these genes expression levels were increased when treated with patulin. Kac changes accompanying degradation of patulin in R. mucilaginosa were also observed. Totally, 130 Kac sites in 103 proteins were differentially expressed under patulin stress. The differentially up expressed modified proteins were mainly involved in tricarboxylic acid cycle and nuclear acid biosynthesis. The differentially down expressed Kac proteins were mainly classified to ribosome, oxidative phosphorylation, protein synthesis and defense to stress process. Our results suggest that patulin exposure prompt R. mucilaginosa to produce a series of actions to resist or degrade patulin, including Kac. In addition, the Kac information in R. mucilaginosa and Kac in response to patulin stress was firstly revealed.

This present study tested the extent to which 2% w/v trehalose enhanced the proteins expression profile of Hanseniaspora uvarum Y3. Furthermore, it explored the relative gene expression of stilbene synthase (StSy), one of the vital defense-related genes found in the skin of grapes. The proteomics profile revealed that 29 proteins were differentially expressed out of which 26 were significantly up-regulated and 3 were download-regulated. The pathogenesis related (PR) and other protein spots were visible at 97.4 kDa and 14.4 kDa. Peroxiredoxin TSA1 and superoxide dismutase were the main proteins involved in defense response and both proteins were significantly up-regulated. The carbohydrate and energy metabolism proteins were also significantly up-regulated. The results revealed that the treatments were associated with substantial increase in peroxidase activity compared to the control. StSy relative gene expression level was observed to increase by 2.5-fold in grapes treated with the pre-enhanced H. uvarum compared to the control.

The occurrence of patulin in fresh apples and apple products is a great burden from health, safety and economic perspectives. Attempts to prevent patulin accumulation in fruits might lead to the excessive use of fungicides. Therefore, guaranteeing the safety of apple foods is crucial for the international apple industry. Recently, literature revealed that application of antagonistic yeasts and other BCAs have been able to disrupt the process of fungal infection and patulin production in apples. Although, over the years the effect of interaction between BCAs and fungi on patulin production has been reported, the exact mechanism(s) of their action remain unclear. Here, the review focused on toxicology and occurrence of PAT; research advances made over the past few years on the interaction between antagonistic yeast, fruits and patulin-producing fungi; the prevalence of patulin in apple fruits and products and the implications of synthetic-fungicide applications. In addition, attention was focused on the mechanism(s) and the enhancement of the biocontrol efficacy of antagonistic for patulin control.

Patulin (PAT) is a mycotoxin produced by some

Citrinin (CIT) is a toxic secondary metabolite produced by fungi belonging to the Penicillium, Aspergillus, and Monascus spp. This toxin has been detected in many agricultural products. In this study, a strain Y3 with the ability to eliminate CIT was screened and identified as Cryptococcus podzolicus, based on the sequence analysis of the internal transcribed spacer region. Neither uptake of CIT by cells nor adsorption by cell wall was involved in CIT elimination by Cryptococcus podzolicus Y3. The extracellular metabolites of Cryptococcus podzolicus Y3 stimulated by CIT or not showed no degradation for CIT. It indicated that CIT elimination was attributed to the degradation of intracellular enzyme(s). The degradation of CIT by C. podzolicus Y3 was dependent on the type of media, yeast concentration, temperature, pH, and initial concentration of CIT. Most of the CIT was degraded by C. podzolicus Y3 in NYDB medium at 42 h but not in PDB medium. The degradation rate of CIT was the highest (94%) when the concentration of C. podzolicus Y3 was 1 × 10⁸ cells/ml. The quantity of CIT degradation was highest at 28°C, and there was no degradation observed at 35°C. The study also showed that acidic condition (pH 4.0) was the most favorable for CIT degradation by C. podzolicus Y3. The degradation rate of CIT increased to 98% as the concentration of CIT was increased to 20 μg/ml. The toxicity of CIT degradation product(s) toward HEK293 was much lower than that of CIT.

The proteomic and lysine acetylation (Kac) changes, accompanying degradation of patulin in Rhodotorula mucilaginosa were analyzed using tandem mass tagging and N6-acetyllysine affinity enrichment followed by LC-MS/MS. Proteomic results showed that expression level of short-chain reductase protein and glutathione S-transferase involved in detoxification was significantly up-regulated. In addition, the expression levels of zinc-binding oxidoreductase and quinone oxidoreductase that are involved in antioxidant process, ABC transport and MFS transport responsible for chemical transport were activated when treated with patulin. The quantitative real time PCR (qRT-PCR) result also indicated these genes expression levels were increased when treated with patulin. Kac changes accompanying degradation of patulin in R. mucilaginosa were also observed. Totally, 130 Kac sites in 103 proteins were differentially expressed under patulin stress. The differentially up expressed modified proteins were mainly involved in tricarboxylic acid cycle and nuclear acid biosynthesis. The differentially down expressed Kac proteins were mainly classified to ribosome, oxidative phosphorylation, protein synthesis and defense to stress process. Our results suggest that patulin exposure prompt R. mucilaginosa to produce a series of actions to resist or degrade patulin, including Kac. In addition, the Kac information in R. mucilaginosa and Kac in response to patulin stress was firstly revealed.

Primarily, chemical pesticides are commonly used to control preharvest and postharvest diseases of fruits and vegetables. However, there is strong public concern regarding the human and environmental health problems that might emanate from the residues of these chemical pesticides. As a result, biocontrol is often preferred due to its safety for humans and animals. The microbial antagonists employed often encounter variable climatic conditions, which affect their efficacy. In this study, the biocontrol efficacy of Hanseniaspora uvarum enhanced with trehalose against Aspergillus tubingensis and Penicillium commune in grapes was investigated.H. uvarum Y3 pretreated with 2.0% w/v trehalose in nutrient yeast dextrose broth (NYDB) before used significantly inhibited the incidence of decay and lesion diameter without affecting the sensory qualities of the grapes stored at either 4 °C or 20 °C. There was also a significant (P 0.05) increase in the population dynamics of H. uvarum that was pretreated with 2% trehalose compared to that of H. uvarum alone. The in vitro assay on spore germination revealed an inhibition of A. tubingensis and P. commune by 85.6% and 87.0% respectively. Scanning electron microscopy results showed that both untreated H. uvarum and H. uvarum pre-treated with the 2% w/v trehalose before use inhibited fungal mycelium and development of grape rot.The biocontrol efficacy of H. uvarum was enhanced against grape rot caused by A. tubingensis and P. commune. The findings indicate the potential applicability of trehalose in the enhancement of H. uvarum. © 2018 Society of Chemical Industry.

A better understanding of the mode of action of postharvest biocontrol agents on fruit surfaces is critical for the advancement of successful implementation of postharvest biocontrol products. This is due to the increasing importance of biological control of postharvest diseases over chemical and other control methods. However, most of the mechanisms involved in biological control remain unknown and need to be explored. Yarrowia lipolytica significantly inhibited blue mold decay of apples caused by Penicillium expansum. The findings also demonstrated that Y. lipolytica stimulated the activities of polyphenoloxidase, peroxidase, chitinase, l-phenylalanine ammonia lyase involved in enhancing defense responses in apple fruit tissue. Proteomic and transcriptomic analysis revealed a total of 35 proteins identified as up- and down-regulated in response to the Y. lipolytica inducement. These proteins were related to defense, biotic stimulus, and stress responses, such as pathogenesis-related proteins and dehydrin. The analysis of the transcriptome results proved that the induced resistance was mediated by a crosstalk between salicylic acid (SA) and ethylene/jasmonate (ET/JA) pathways. Y. lipolytica treatment activated the expression of isochorismate synthase gene in the SA pathway, which up-regulates the expression of PR4 in apple. The expression of 1-aminocyclopropane-1-carboxylate oxidase gene and ET-responsive transcription factors 2 and 4, which are involved in the ET pathway, were also activated. In addition, cytochrome oxidase I, which plays an important role in JA signaling for resistance acquisition, was also activated. However, not all of the genes had a positive effect on the SA and ET/JA signal pathways. As transcriptional repressors in JA signaling, TIFY3B and TIFY11B were triggered by the yeast, but the gene expression levels were relatively low. Taken together, Y. lipolytica induced the SA and ET/JA signal mediating the defense pathways by stimulating defense response genes, such as peroxidase, thaumatin-like protein, and chitinase 4-like, which are involved in defense response in apple. [Formula: see text] Copyright © 2017 The Author(s) This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Apple is one of the largely grown fruits in China, and it suffers great economic losses caused by Penicillium expansum infection every year. In the present study, we ascertained the efficacy of Meyerozyma guilliermondii enhanced by 200 μmol/L methyl jasmonate (MeJA) in controlling the postharvest blue mold decay of apples and the possible mechanisms involved. The results demonstrated that the biological control ability of M. guilliermondii induced by MeJA in restraining P. expansum infection in apples. The efficacy of M. guilliermondii induced by MeJA significantly decreased the decay incidence and lesion diameter of apples. When treated with M. guilliermondii induced by MeJA, the decay incidence of apples was only 21.6%, while apples treated with M. guilliermondii was 42.4%. M. guilliermondii induced by MeJA also reduced the germ tube length, spore germination rate of P. expansum in PDB and colony diameter of P. expansum in PDA. The results also showed that antagonistic yeast induced by MeJA proliferated better in apple wounds and surface at 4 °C or 20 °C. Meanwhile, the activities of resistance-related peroxidase (POD), polyphenol oxidase (PPO), phenylalanine ammonia-lyase (PAL), Catalase (CAT), and the antibacterial substances of flavonoid contents, total phenolic content were all increased. The results manifested that M. guilliermondii induced by MeJA increased the expression levels of defense-related enzymes in apples.

Recently a species in the genus Talaromyces, a uniseriate species of Aspergillus section Nigri and an isolate each of two widespread species, Penicillium rubens and P. commune, were reported to produce ochratoxin A. This claim was based on insufficient biological and chemical data. We propose a list of criteria that need to be met before an unexpected mycotoxin producer is reported. There have only been convincing data on ochratoxin A production for Penicillium verrucosum, P. nordicum, P. thymicola, all from Penicillium series Verrucosa, and from species in three sections of Aspergillus: section Circumdati, section Nigri and section Flavi.

Synthetic fungicides are commonly employed for the control of postharvest diseases of fruits. However, due to health concerns about the use of these chemicals, alternative control methods including biocontrol based on antagonistic yeasts are gaining in popularity. In this study, we investigated the effects of two biocontrol yeasts, Rhodotorula mucilaginosa strain 3617 and Rhodotorula kratochvilovae strain LS11, on blue mold and patulin (PAT) contamination caused by Penicillium expansum strains PY and FS7 in artificially inoculated Fuji apples stored at 20°C for 9 days. To correlate the development of the P. expansum strains in yeast-treated and untreated apples with PAT production, we quantified their biomass in the infected fruits using a recently published quantitative real-time polymerase chain reaction method based on specific primers for patF, a gene from P. expansum that is involved in PAT biosynthesis. Both yeasts significantly reduced the disease incidence caused by the two strains of P. expansum up to 5–7 days of incubation, and lowered their biomass and the progression of symptoms up to 9 days. Interestingly, both yeasts strains increased the rate of PAT production (expressed as ng patulin/μg fungal DNA) by the two pathogenic strains. Nevertheless, both biocontrol agents reduced the total PAT contamination, especially in the case of P. expansum strain FS7, the higher PAT producer of the two tested P. expansum strains. Comparing between the yeast strains, R. kratochvilovae LS11 was more effective than R. mucilaginosa 3617 for the control of P. expansum.

Ochratoxin A (OTA) contamination has been established as a world-wide problem. In this study, the strains with the ability of OTA production were screened by analyzing the green fluorescence of the isolates colonies from the grapes in Zhenjiang with 365 nm UV light and confirmed by HPLC with fluorescent detection (HPLC-FLD). The results showed that seven isolates acquired the characteristic of the fluorescence, of which only five showed the ability of OTA production as confirmed by HPLC-FLD analysis. The five OTA-producing strains were identified based on comparative sequence analysis of three conserved genes (ITS, BenA and RPB2) of the strains, and they are Talaromyces rugulosus (O1 and Q3), Penicillium commune (V5-1), Penicillium rubens (MQ-5) and Aspergillus aculeatus (MB1-1). There are two Penicillium species of the five OTA-producing strains and our study is the first to report that P. rubens, T. rugulosus and A. aculeatus can produce OTA. This work would contribute to comprehensively understanding the fungi with an OTA-producing ability in grapes before harvest and then take effective measures to prevent OTA production.