Postharvest Diseases Of Fruits Research Articles

Research progress of volatile organic compounds produced by plant endophytic bacteria in control of postharvest diseases of fruits and vegetables

Pathogen infestation results in significant losses of fruits and vegetables during handling, transportation, and storage. The use of synthetic fungicides has been a common measure for controlling plant pathogens. However, their excessive use of chemicals has led to increased environmental pollution, leaving large amounts of chemicals in agricultural products, posing a threat to human and animal health. There is now an increasing amount of research activities to explore safer and more innovative ways to control plant pathogens. In this regard, endophytic bacteria contribute significantly. Endophytic bacteria are ubiquitous in the internal tissues of plants without causing damage or disease to the host. Due to their high volatility and difficulties in residue in fruits and vegetables, volatile organic chemicals (VOCs) produced by endophytic bacteria have received a lot of attention in recent years. VOCs are a potential biofumigant for the effective control of postharvest fruits and vegetables diseases. This review focuses mainly on the recent progress in using endophytic bacteria VOCs to control post-harvest fruits and vegetables disease. This review provides a brief overview of the concept, characteristics, and summarises the types, application effect, and control mechanisms of endophytic bacterial VOCs. The research area that is being developed has great application value in agriculture and living practice.

Essential Oils in Postharvest Treatment against Microbial Spoilage of the Rosaceae Family Fruits

Fruits undergo numerous chemical, physical, and microbiological changes during storage that shorten their postharvest life, reducing shelf-life and boosting food loss. Food quality and safety are seriously threatened by postharvest infections, one of the factors behind postharvest deterioration and mycotoxin contamination in fruits. The control of postharvest deterioration is a big concern because there are few management methods available. Several attempts have been undertaken to prevent the microbial degradation of fresh food at the postharvest stage without using synthetic fungicides, which are dangerous for the environment and people’s health. A good substitute for synthetic fungicides among them is the use of natural plant compounds, such as essential oils included or not included in the edible coatings. This review’s aim was to collect information from the scientific literature on the biological activity of essential oil, with or without edible coatings, against pathogens that cause the postharvest spoilage of many fruit belonging to Rosaceae family in order to develop appropriate substitute tactics for synthetic fungicides in the treatment of postharvest fruit diseases. Advances and obstacles surrounding emerging methods that may be useful for enhancing the effectiveness and dependability of essential oils were evaluated.

Postharvest Biology and Technology of Loquat (Eriobotrya japonica Lindl.)

Loquat (Eriobotrya japonica Lindl.) fruit is a rich source of carotenoids, flavonoids, phenolics, sugars, and organic acids. Although it is classified as a non-climacteric fruit, susceptibility to mechanical and physical bruising causes its rapid deterioration by moisture loss and postharvest decay caused by pathogens. Anthracnose, canker, and purple spot are the most prevalent postharvest diseases of loquat fruit. Cold storage has been used for quality management of loquat fruit, but the susceptibility of some cultivars to chilling injury (CI) consequently leads to browning and other disorders. Various techniques, including cold storage, controlled atmosphere storage, hypobaric storage, modified atmosphere packaging, low-temperature conditioning, heat treatment, edible coatings, and postharvest chemical application, have been tested to extend shelf life, mitigate chilling injury, and quality preservation. This review comprehensively focuses on the recent advances in the postharvest physiology and technology of loquat fruit, such as harvest maturity, fruit ripening physiology, postharvest storage techniques, and physiological disorders and diseases.

Essential Oils and Chitosan Applications to Protect Apples against Postharvest Diseases and to Extend Shelf Life

Apple fruits are susceptible to pathogenic fungi such as Botrytis cinerea and Penicillium expansum which are responsible for significant pre- and postharvest fruit losses. Given the strong restriction in the use of synthetic agrochemicals, especially during the postharvest phase, alternatives are currently sought for a more sustainable management of apple storage. The antifungal activity of thyme, clove, anise, camphor, and juniper essential oils (EOs) was evaluated with in vitro tests and the minimum inhibitory concentration (MIC) was determined. Thyme and anise EOs showed a MIC value of 0.5 and 1 mL L−1 against B. cinerea, respectively. A MIC of 0.5 mL L−1 was found for clove EO against P. expansum. Camphor and juniper EOs were found to be less effective. Although in those experiments the antifungal activity of EOs was proven, when EOs were applied in in vivo conditions they did not demonstrate the same effectiveness. In order to preserve EO inhibitory performances, edible coatings combining polysaccharide matrices (chitosan, arabic gum, and xanthan gum) with EOs were tested. After considering consistency, uniform coverage of the fruit surface, and antifungal properties of the matrix, chitosan was identified as the most suitable component for EO encapsulation. Treatments with chitosan in combination with thyme EO on apple fruits (cv. ‘Braeburn’) showed inhibitory effects on infection caused by B. cinerea (−48% of infected wounds compared to untreated). Similarly, clove EO combined with chitosan reduced the Penicillium infections in apple cv. ‘Golden Delicious’ by 62%. These results therefore suggest the effectiveness of the use of EOs encapsulated with chitosan for the control of postharvest diseases of apple fruits during storage.

Effect of L-cysteine treatment to induce postharvest disease resistance of Monilinia fructicola in plum fruits and the possible mechanisms involved

Plum is an important stone fruit in China, but the fruit is easily perishable and susceptible to infection by pathogens. Traditionally, synthetic fungicides are used to control diseases. However, the side effects of fungicides should not be ignored. Cysteine, generally recognized as safe (GRAS) amino acid, has been reported to play roles in the plant abiotic stress response, but little is known about the role of cysteine to control postharvest diseases in fruits. Therefore, this study was designed to investigate the effect of L-cysteine treatment on control of postharvest brown rot in artificially inoculated plum fruits and the possible biocontrol mechanisms involved. Postharvest plum fruits were inoculated with 1, 10, 100 and 1000 mg L−1 L-cysteine. 100 mg L−1 L-cysteine treatment effectively controlled brown rot in artificially inoculated plum fruits by inducing resistance. Furthermore, 100 mg L−1 L-cysteine treatment increased the activities of glucose-6-phosphate dehydrogenase (G6PDH) and 6-phosphogluconate dehydrogenase (6PGDH), enhanced the content of NADPH of the pentose phosphate pathway, as well as improved the contents of H2O2 and some amino acids in the artificially inoculated plum fruits. 100 mg L−1 L-cysteine treatment also elevated the antioxidant content (AsA, GSH) and the antioxidant enzymes activities (APX, GR, MDAR, DHAR) of the ascorbate-glutathione (AsA-GSH) pathway. The protective effects of L-cysteine treatment on postharvest plum fruits likely be due to activating some defense-related responses of the fruit against infection. L-cysteine treatment is a safe promising method for controlling postharvest brown rot in plum fruits.

2-hydroxy-3-phenylpropanoic acid suppressed the growth of Alternaria alternata through damaging cell membrane integrity and modulating reactive oxygen species metabolism

Black spot rot caused by Alternaria alternata is one of the major postharvest disease of apple fruit during logistic. This study evaluated in vitro inhibitory effect of 2-hydroxy-3-phenylpropanoic acid (PLA) at various concentrations on A. alternata and the possible mechanisms involved in its action. Results showed that different concentrations of PLA inhibited conidia germination and mycelial growth of A. alternata in vitro, and 1.0 g L−1 was the lowest effective concentration to suppress A. alternata growth. Moreover, PLA significantly reduced relative conductivity and increased malondialdehyde and soluble protein contents. PLA also increased H2O2 and dehydroascorbic acid contents, but reduced ascorbic acid content. Additionally, PLA treatment inhibited catalase, ascorbate peroxidase, monodehydroascorbate acid reductase, dehydroascorbic acid reductase and glutathione reductase activities, whereas promoted superoxide dismutase activity. All these findings suggest that the possible mechanisms involved in the inhibitory effect of PLA on A. alternata included damaging the cell membrane integrity to cause electrolyte leakage and destroying reactive oxygen species balance.

Hydrogen sulfide enhances resistance to Penicillium italicum by activating phenylpropanoid metabolism in postharvest navel orange fruit

An effective prevention treatment in postharvest fruit diseases is helpful in maintaining fruit quality and prolonging shelf life. In this study, we aimed to investigate whether hydrogen sulfide (H2S) enhances resistance to Penicillium italicum by activating phenylpropanoid metabolism in postharvest navel orange fruit. The findings showed that 25 μL/L H2S fumigation alleviated the disease symptoms and lesion area of P. italicum-inoculated navel orange fruit. RTqPCR analysis revealed that H2S treatment upregulated the transcription levels of phenylpropanoid biosynthesis (CitC4H, Cit4CL, CitCYP98A, CitCAD, CitCHI, and CitCHS) and metabolite-related genes (CitPAL, CitGLU, CitPOD, and CitCSE). Meanwhile, H2S upregulated the transcripts of MYB and WRKY transcription factors and had similar expression patterns to phenylpropanoid metabolism-related genes. Correlation analysis showed that H2S-promoted accumulation patterns of total phenols, flavonoids, and lignin were positively correlated with phenylpropanoid metabolism-related gene transcripts. In addition, sodium hydrosulfide (NaHS, H2S donor)-released H2S restrained P. italicum mycelium growth. Treatment with 25 and 50 mmol/L NaHS markedly decreased the mycelium weight while increasing extracellular conductivity and membrane leakage. Overall, these findings indicated that H2S could induce resistance in navel orange fruit because of its inhibitory role and positive regulation of many phenylpropanoid metabolism-modifying genes as well as possibly candidate MYB and WRKY transcription factors.

Transcription factor CsERF1B regulates postharvest citrus fruit resistance to Penicillium digitatum

Green mold, caused by Penicillium digitatum (P. digitatum), is among the most important postharvest disease of citrus fruit in terms of economic losses. Previous studies reported that AP2/ERFs in citrus pericarp positively respond to P. digitatum infection; therefore, it is presumed that AP2/ERFs could participate in the regulation of the fruit resistance response. However, limited research is available on AP2/ERF transcription factors in regulating the disease resistance of citrus fruit. In the present study, the regulatory role of CsERF1B in citrus green mold was clarified and the regulatory mechanism was initially explored. In our work, CsERF1B is a transcriptional activator with a nuclear localization signal. Transient overexpression of CsERF1B in citrus pericarp significantly enhanced fruit resistance to green mold and induced upregulated expression of pathogenesis-related genes in the pericarp. CsERF1B directly activated lignin synthesis genes, increased the activities of related enzymes, and promoted the accumulation of lignin. CsERF1B directly activated the genes related to jasmonic acid signaling and immunity, indirectly activated genes related to chitinase, and it also directly repressed salicylic acid signaling pathway genes, thus participating in the regulation of fruit disease resistance. This research provides novel insights into the mechanisms of disease resistance regulation by AP2/ERF transcription factors in citrus fruit.

Biocontrol of post-harvest tomato rot caused by Alternaria arborescens using Torulaspora indica

ABSTRACT An important concern in modern agriculture is the production of healthy foods. This has resulted in an increasing number of studies on alternative plant protection strategies such as biological control. Yeasts have received considerable attention as biological control agents against postharvest fungal diseases of fruits and vegetables. Here, we describe the potential of the yeast strain Torulaspora indica as a biological control agent against Alternaria arborescens, causal agent of tomato fruits decay. In vitro and in vivo assays were used to evaluate the interaction of Torulaspora indica (CCA5S55) and Alternaria arborescens (ABS2). This was followed by the evaluation of putative mechanisms controlling fungal development. Our results suggest that the production of volatile compounds and competition for nutrients are putative mechanisms by which T. indica inhibits A. arborescens growth in vitro. The results of in vivo assays indicate a reduction in the number of A. arborescens-induced lesions in tomato fruits in the presence of T. indica.

Perfume Guns: Potential of Yeast Volatile Organic Compounds in the Biological Control of Mycotoxin-Producing Fungi.

Pathogenic fungi in the genera Alternaria, Aspergillus, Botrytis, Fusarium, Geotrichum, Gloeosporium, Monilinia, Mucor, Penicillium, and Rhizopus are the most common cause of pre- and postharvest diseases of fruit, vegetable, root and grain commodities. Some species are also able to produce mycotoxins, secondary metabolites having toxic effects on human and non-human animals upon ingestion of contaminated food and feed. Synthetic fungicides still represent the most common tool to control these pathogens. However, long-term application of fungicides has led to unacceptable pollution and may favour the selection of fungicide-resistant mutants. Microbial biocontrol agents may reduce the incidence of toxigenic fungi through a wide array of mechanisms, including competition for the ecological niche, antibiosis, mycoparasitism, and the induction of resistance in the host plant tissues. In recent years, the emission of volatile organic compounds (VOCs) has been proposed as a key mechanism of biocontrol. Their bioactivity and the absence of residues make the use of microbial VOCs a sustainable and effective alternative to synthetic fungicides in the management of postharvest pathogens, particularly in airtight environments. In this review, we will focus on the possibility of applying yeast VOCs in the biocontrol of mycotoxigenic fungi affecting stored food and feed.

Identification and Fungal Biology of Post-harvest Fungi Associated with Amla Fruits and It's In Vitro Control Measures

Post-harvest spoilage of Amla fruits is one of the major problems which reduces the economic quality of the fruits. The goal of the present study was to identify the post-harvest fungal pathogens associated with Amla fruits based on morphological and molecular characteristics, growth characteristics of the fungi, and their eco-friendly control measures. The fungi were identified as Penicillium rolfsii Thom., Penicillium herquei Bainier & Sartory, Aspergillus aculeatus Iizuka, Aspergillus terreus Thom., and Mucor sp. Frasen. Penicillium rolfsii and Aspergillus aculeatus were preferred to grow on Richard Agar medium; Penicillium herquei grew the maximum on Potato Sucrose Agar medium; Aspergillus terreus was found to grow irrespective of culture media and Mucor sp. grew on all the tested media except Richard Agar medium. The optimum temperatures were recorded at 25 to 35℃ for all of the fungi except Mucor sp., which preferred to grow at 15℃. Aspergillus aculeatus was able to grow on a broad range of pH (5 to 9); Penicillium rolfsii, Penicillium herquei, and Aspergillus terreus were grown better at neutral to slightly alkaline pH, while Mucor sp. on slightly acidic conditions. Aqueous crude extracts of garlic and black cumin were found to show inhibitory activity against all the fungi. Food preservative sodium benzoate was found to be the most efficient against fungal pathogens. Based on our findings, it is suggested that garlic extract and sodium benzoate could be used to manage the fungal growth associated with post-harvest Amla fruit diseases.

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.

Biological control of major postharvest fungal diseases of apple using two Lamiaceae extracts

This study aimed to evaluate the antifungal activity of the aqueous extracts of two wild Lamiaceae species against P. expansum and B. cinerea and the impact of these treatments on fruit quality parameters. The in vitro results showed significant effect of the two aqueous extracts on both fungi mycelial growth. A. alpinus exhibited high antifungal efficacy against P. expansum with an inhibition rate ranging from 34.32 to 90.76% whereas T. vulgaris exhibit an inhibition rate against B. cinerea ranging from 61.87 to 97.94%. These results indicated that A. alpinus and T. vulgaris were extremely potent against both pathogens with an EC50 ranging from 0.82 to 2.39%. The in vivo experiments on apple fruit were very promising with an approximate efficacy varying from 64 to 79% with no impacts on fruit quality parameters. These results provide evidence that both plant species are an effective alternative to control postharvest diseases of fruit.

Chemical Composition Profiling and Antifungal Activity of Saffron Petal Extract.

Numerous fungal plant pathogens can infect fresh fruits and vegetables during transit and storage conditions. The resulting infections were mainly controlled by synthetic fungicides, but their application has many drawbacks associated with the threatened environment and human health. Therefore, the use of natural plants with antimicrobial potential could be a promising alternative to overcome the side effects of fungicides. In this regard, this study aimed at evaluating the antifungal activity potential of saffron petal extract (SPE) against three mains important fungal pathogens: Rhizopus stolonifer, Penicillium digitatum and Botritys cinerea, which cause rot decay on the tomato, orange and apple fruits, respectively. In addition, the organic composition of SPE was characterized by attenuated total reflection Fourier transform infrared (ATR-FT-IR) spectroscopy and its biochemical, and gas chromatography-mass spectrometry (GC-MS) analyses were carried out. The obtained results highlighted an increased inhibition rate of the mycelial growth and spore germination of the three pathogenic fungi with increasing SPE concentrations. The mycelial growth and spore germination were completely inhibited at 10% of the SPE for Rhizopus stolonifer and Penicillium digitatum and at 5% for B. cinerea. Interestingly, the in vivo test showed the complete suppression of Rhizopus rot by the SPE at 10%, and a significant reduction of the severity of grey mold disease (37.19%) and green mold, when applied at 5 and 10%, respectively. The FT-IR spectra showed characteristic peaks and a variety of functional groups, which confirmed that SPE contains phenolic and flavonoid components. In addition, The average value of the total phenolic content, flavonoid content and half-maximal inhibitory concentration (IC50) were 3.09 ± 0.012 mg GAE/g DW, 0.92 ± 0.004 mg QE/g DW and 235.15 ± 2.12 µg/mL, respectively. A volatile analysis showed that the most dominant component in the saffron petal is 2(5H)-Furanone (92.10%). Taken together, it was concluded that SPE could be used as an alternative to antioxidant and antifungal compounds for the control of postharvest diseases in fruits.

Overview of management practices with the use of biocontrols, natural products, and conventional fungicides to combat pre- and postharvest diseases of peach and nectarine fruit

Overview of management practices with the use of biocontrols, natural products, and conventional fungicides to combat pre- and postharvest diseases of peach and nectarine fruit

Deciphering the role of endophytic microbiome in postharvest diseases management of fruits: Opportunity areas in commercial up-scale production.

As endophytes are widely distributed in the plant's internal compartments and despite having enormous potential as a biocontrol agent against postharvest diseases of fruits, the fruit-endophyte-pathogen interactions have not been studied detail. Therefore, this review aims to briefly discuss the colonization patterns of endophytes and pathogens in the host tissue, the diversity and distribution patterns of endophytes in the carposphere of fruits, and host-endophyte-pathogen interactions and the molecular mechanism of the endophytic microbiome in postharvest disease management in fruits. Postharvest loss management is one of the major concerns of the current century. It is considered a critical challenge to food security for the rising global population. However, to manage the postharvest loss, still, a large population relies on chemical fungicides, which affect food quality and are hazardous to health and the surrounding environment. However, the scientific community has searched for alternatives for the last two decades. In this context, endophytic microorganisms have emerged as an economical, sustainable, and viable option to manage postharvest pathogens with integral colonization properties and eliciting a defense response against pathogens. This review extensively summarizes recent developments in endophytic interactions with harvested fruits and pathogens-the multiple biocontrol traits of endophytes and colonization and diversity patterns of endophytes. In addition, the upscale commercial production of endophytes for postharvest disease treatment is discussed.

The role of essential oils in maintaining the postharvest quality and preservation of peach and other fruits.

Fruits are highly susceptible to postharvest losses induced majorly by postharvest diseases. Peach are favored by consumers because of their high nutritional value and delicious taste. However, it was easy to be affected by fungal infection. The current effective method to control postharvest diseases of fruits is to use chemical fungicides, but these chemicals may cause adverse effects on human health and the residual was potentially harmful to nature and the environment. So, it is especially important to develop safe, non-toxic, and highly effective strategies for the preservation of the fruits. Essential oil, as a class of the natural bacterial inhibitor, has been proven to exhibit strong antibacterial activity, low toxicity, environmental friendliness, and induce fruit resistance to microorganism, which could be recognized as one of the alternatives to chemical fungicides. This paper reviews the research progress of essential oils (Eos) in the storage and preservation of fruits, especially the application in peach, as well as the application in active packaging such as edible coatings, microcapsules, and electrospinning loading. Electrospinning can prepare a variety of nanofibers from different viscoelastic polymer solutions, and has broad application prospects. The paper especially summarizes the application of the new Eos technology on peach. The essential oil with thymol, eugenol, and carvacrol as the main components has a better inhibitory effect on the postharvest disease of peaches, and can be further applied. PRACTICAL APPLICATIONS: As an environmentally friendly natural antibacterial agent, essential oil can be used as a substitute for chemical preservatives to keep fruits fresh. This paper summarizes the different preservation methods of essential oils for fruits, and especially summarizes the different preservation methods of essential oils for peaches after harvesting, as well as their inhibitory effects on pathogenic fungi. It could provide ideas for preservation of fruits and vegetables by essential oils.

Pichia caribbica combined with oligochitosan controlling black spot of tomatoes and the regulation on ROS metabolism of the fruits

Black spot caused by Alternaria alternata is one of the main postharvest diseases of tomato fruits. This research aimed to investigate biocontrol efficacy of Pichia caribbica combined with oligochitosan (OCH) against black spot of tomato fruits and explore the mechanisms involved in improved disease resistance of the fruits by yeast combined with OCH based on analysis of reactive oxygen species (ROS) metabolism. The results indicated that in comparison with P. caribbica alone, yeast combined with OCH (2000 μg/mL) could further reduce black spot of tomato fruits. P. caribbica combined with OCH increased NADPH oxidase (NOX) activity in the fruits compared with the control and the group treated with yeast alone. The activities of enzymatic system for ROS scavenging including antioxidant enzymes, enzymes involved in ascorbate–glutathione (AsA-GSH) and GPX (glutathione peroxidase) cycles, and glutathione S-transferase (GST) in the fruits were induced by yeast combined with OCH. Additionally, the contents of ascorbic acid (AsA) and glutathione (GSH) belonging to non-enzymatic system for ROS scavenging were enhanced in the fruits. Collectively, the induction of NOX and the improvement of enzymatic and non-enzymatic systems for ROS scavenging resulted in the decrease in O2–·, H2O2 and malondialdehyde (MDA) production in the fruits, thus promoting the disease resistance of tomato fruits. This research will provide new ideas for the control of postharvest diseases of tomato fruits.

Tryptophan enhances biocontrol efficacy of Metschnikowia citriensis FL01 against postharvest fungal diseases of citrus fruit by increasing pulcherriminic acid production

The aim of this work was to study the capability and mechanism of enhancing the yield of pulcherriminic acid (PA) produced by Metschnikowia citriensis FL01 with the help of tryptophan for the control of postharvest diseases on citrus caused by Penicillium italicum, Geotrichum citri-aurantii and Penicillium digitatum. The adding of 10 mmol/L tryptophan to the growth medium resulted in the widest pulcherrimin pigment zone produced by M. citriensis FL01. The adding of tryptophan to the growth medium upregulated A3136 and A3022 gene expression (responsible for leucyl-tRNA biosynthesis from leucine), downregulated A1350 gene expression (responsible for the biosynthesis of leucine to branched-chain fatty acids), and decreased the content of intracellular leucine in M. citriensis FL01, speculating that the addition of tryptophan in the growth medium induced leucine conversion toward leucyl-tRNA in M. citriensis FL01. Moreover, the adding of tryptophan to the growth medium upregulated PULs (responsible PA biosynthesis) and Snf2 (transcriptional regulator) gene expression and promoted intracellular, extracellular or total PA production by M. citriensis FL01 in liquid medium. In addition, the addition of tryptophan in the growth medium showed no effect on the growth of M. citriensis FL01 itself in liquid medium, while the population dynamics in citrus fruit wounds of M. citriensis FL01 with the addition of tryptophan in the growth medium were increased compared with those of M. citriensis FL01. What's more, M. citriensis FL01 with the addition of tryptophan in the growth medium completely inhibited the growth of pathogens in vitro. The disease incidences and lesion diameters of blue mold, sour rot and green mold on citrus fruit were lower in group which treated with M. citriensis FL01 containing tryptophan in the growth medium than that treated with M. citriensis FL01 alone. Overall, the postharvest biocontrol of citrus with M. citriensis FL01 containing 10 mmol/L tryptophan in the growth medium is a promising approach to protect these fruits from blue mold, sour rot and green mold.

Genome-wide identification of the CsPAL gene family and functional analysis for strengthening green mold resistance in citrus fruit

Phenylalanine aminolyase (PAL) is a key rate-limiting enzyme. It catalyzes the initial step of the phenylpropane metabolic pathway. PAL is involved in the regulation of fruit diseases, but the specific function of the PAL gene in the regulation of postharvest fruit diseases is unknown. In this study, we identified four CsPAL members in citrus, including CsPAL1-CsPAL4. Based on physicochemical properties, gene structure, protein structure, protein sequence, and phylogenetic relationship analysis, all four CsPALs are predicted to have catalytic activity and take part in the disease resistance of citrus fruit to green mold. In addition, using Agrobacterium-mediated transient overexpression, all four CsPALs were shown to improve the tolerance of citrus fruit to green mold. Measurements of secondary metabolites in peel samples from the four transient overexpression groups showed a significant increase in both flavonoids and total phenols and a significant decrease in lignin content. For the first time, four CsPAL members were identified from the citrus genome, demonstrating that they are all implicated in the gene function of citrus fruit resistance to green mold through the elevation of flavonoids and total phenols but not lignin.