Postharvest Gray Mold Research Articles

Investigating the action model of the resistance enhancement induced by bacterial volatile organic compounds against Botrytis cinerea in tomato fruit

IntroductionInducing natural resistance against pathogen infection in postharvest tomatoes is a sustainable strategy for reducing postharvest losses. The action model underlying the resistance enhancement of tomatoes induced by bacterial volatile organic compounds (VOCs) against Botrytis cinerea, however, have not been explored.MethodsIn this study, RNA-seq, metabolomics and physiological analysis were used to evaluate global change of defense response induced by VOCs in tomatoes.ResultsThe application of VOCs inhibited the damage to tomatoes caused by B. cinerea. VOCs treatment had remarkable beneficial effects on the activities of the main defence-related enzymes, including chitinases, glucanases, peroxidases, ascorbate peroxidases, polyphenol oxidases, and phenylalanine ammonia-lyases. The expression of response genes involved in salicylic acid and jasmonic acid biosynthesis and signalling pathways was enhanced upon VOCs treatment. Metabolomics data demonstrated that VOC treatment triggered the accumulation of phenolic acids, including substrates in phenolic acid biosynthesis pathways, hydroxycinnamic acid, hydroxybenzoic acid, and their derivatives. Transcriptomics analysis and qRT-PCR verification revealed that VOCs treatment significantly upregulates the expression of core genes related to phenolic acid biosynthesis, specifically in shikimate pathway (SlDAHPS, SlSDH, SlCS, and SlADT3) and phenylalanine metabolic pathway (SlPAL, Sl4CL, SlBAHD1, SlCYP98A2 and SlCAP84A1).DiscussionResults confirmed that VOCs enhanced tomatoes postharvest resistance against B. cinerea by regulating defence enzyme activity, SA/JA signalling, and phenolic acid biosynthesis pathway. This study provides new insights into the mechanisms by which VOCs fumigation manages postharvest grey mould in tomatoes.

Combined application of the endophyte Bacillus K1 and sodium dehydroacetate alleviates postharvest gray mold in grapes

Botrytis cinerea, which causes postharvest gray mold, is a primary pathogen that limits grape shelf-life and consumption and causes substantial yield loss worldwide. The combined use of biocontrol agents and food additives has attracted increasing interest. The effects of combined treatment with the endophyte Bacillus subtilis K1 and sodium dehydroacetate (SD) on the occurrence of gray mold and maintenance of grape fruit quality were studied. Treatment with a K1 suspension (1 × 108 CFU/ml) combined with 0.32 g/L SD resulted in markedly improved control of B. cinerea on grapes. The disease incidence and severity in the groups treated with K1 alone or in combination with SD were significantly lower than those in the control groups (P < 0.05) when the mixtures were applied 2 h after pathogen inoculation. Moreover, application of the mixture could maintain the appearance, firmness, total soluble solid (TSS) content and titratable acidity (TA) of grape fruit. Furthermore, the combination triggered increases in the activities of defense-related enzymes such as peroxidase (POD), phenylalanine ammonia lyase (PAL), catalase (CAT), superoxide dismutase (SOD) and polyphenol oxidase (PPO). Additionally, it could increase the vitamin C content. Thus, appropriate combinations of biocontrol agents and chemical reagents can provide effective protection against postharvest decay.

Enhancing the Storage Longevity of Apples: The Potential of Bacillus subtilis and Streptomyces endus as Preventative Bioagents against Post-Harvest Gray Mold Disease, Caused by Botrytis cinerea.

Gray mold, caused by Botrytis cinerea Pers. Fr., is one of the most vital plant diseases, causing extensive pre- and post-harvest losses in apple fruits. In the current study, we isolated and identified two potential endophytic bioagents, Bacillus subtilis and Streptomyces endus. Both bioagents exhibited a potent fungistatic effect against B. cinerea under both in vitro and in planta conditions. Moreover, two experiments were carried out; (i) the first experiment was conducted at room temperature after artificial inoculation with B. cinerea to monitor the progression of the infection and the corresponding biochemical responses of the apples. Our in vivo findings showed that the treated B. cinerea-infected apple fruits with the cell-free bacterial filtrate of B. subtilis and S. endus (dipping or wrapping) significantly reduced the rotten area of the treated apple at room temperature. Additionally, B. subtilis and S. endus enhanced the enzymatic (POX and PPO) and non-enzymatic (phenolics and flavonoids) antioxidant defense machinery in treated apples. (ii) The second experiment focused on the preventive effects of both bioagents over a 90-day storage period at 1 °C of healthy apples (no artificial inoculation). The application of both bacterial filtrates prolonged the storage period, reduced the relative weight loss, and maintained high-quality parameters including titratable acidity, firmness, and total soluble solids of apple fruits under cold storage at 1 °C. The Kaplan-Meier analysis of rotten apples over 90 days during cold storage showed that the treated apples lasted longer than the non-treated apples. Moreover, the lifespan of apple fruits dipped in the culture filtrate of B. subtilis, or a fungicide, was increased, with no significant differences, compared with the non-treated apples. The current results showed the possibility of using both bioagents as a safe and eco-friendly alternative to chemical fungicides to control gray mold disease in apples.

Bio-perfume guns: Antifungal volatile activity of Bacillus sp. LNXM12 against postharvest pathogen Botrytis cinerea in tomato and strawberry

Gray mold disease, caused by Botrytis cinerea is a major postharvest disease impacting fruits such as strawberries and tomatoes. This study explores the use of volatile organic compounds (VOCs) produced by Bacillus spp. as eco-friendly biocontrol agents against B. cinerea. In vitro experiments demonstrated that VOCs from Bacillus sp. LNXM12, B. thuringiensis GBAC46, and B. zhanghouensis LLTC93-VOCs inhibited fungal growth by 61.2%, 40.5%, and 21.6%, respectively, compared to the control. LNXM12 was selected for further experiments due to its highest control efficacy of 58.3% and 76.6% on tomato and strawberry fruits, respectively. The LNXM12 VOCs were identified through gas chromatography–mass spectrometry (GC–MS) analysis, and 22 VOCs were identified. Synthetic VOCs with the highest probability percentage, namely ethyloctynol, 3-methyl-2-pentanone (3M2P), 1,3-butadiene-N, N-dimethylformamide (DMF), and squalene were used in experiments. The results showed that the synthetic VOCs ethyloctynol and 3M2P were highly effective, with an inhibition rate of 56.8 and 57.1% against fungal mycelium radial growth at 120 μg/mL on agar plates. Trypan blue staining revealed strongly disrupted, deeper blue, and lysed mycelium in VOC-treated B. cinerea. The scanning and transmission electron microscope (SEM and TEM) results showed that fungal mycelium was smaller, irregular, and shrunken after synthetic VOC treatments. Furthermore, the synthetic VOCs Ethyloctynol and 3M2P revealed high control efficacy on tomatoes and strawberries infected by B. cinerea. The control efficacy on leaves was 67.2%, 66.1% and 64.5%, 78.4% respectively. Similarly, the control efficiency on fruits was 45.5%, 67.3% and 46.3% 65.1%. The expression of virulence genes in B. cinerea was analyzed, and the results revealed that selected genes BcSpl1, BcXyn11A, BcPG2, BcNoxB, BcNoxR, and BcPG1 were downregulated after VOCs treatment. The overall result revealed novel mechanisms by which Bacillus sp. volatiles control postharvest gray mold disease.

Identification and evaluation of an endophytic antagonistic yeast for the control of gray mold (Botrytis cinerea) in apple and mechanisms of action

Gray mold, caused by Botrytis cinerea, is a prevalent postharvest disease of apple that limits their shelf life, resulting in significant economic losses. The use of antagonistic microorganisms has been shown to be an effective approach for managing postharvest diseases of fruit. In the present study, an endophytic yeast strain PGY-2 was isolated from apples and evaluated for its biocontrol efficacy against gray mold and its mechanisms of action. Results indicated that strain PGY-2, identified as Bullera alba, reduced the occurrence of gray mold on apples and significantly inhibited lesion development in pathogen-inoculated wounds. Gray mold control increased with the use of increasing concentrations of PGY-2, with the best disease control observed at 108 cells/mL. Notably, Bullera alba PGY-2 did not inhibit the growth of Botrytis cinerea in vitro indicating that the yeast antagonist did not produce antimicrobial compounds. The rapid colonization and stable population of PGY-2 in apple wounds at 4 °C and 25 °C confirmed its ability to compete with pathogens for nutrients and space. PGY-2 also had a strong ability to form a biofilm and enhanced the activity of multiple defense-related enzymes (POD, PPO, APX, SOD, PAL) in host tissues. Our study is the first time to report the use of Bullera alba PGY-2 as a biocontrol agent for postharvest diseases of apple and provide evidence that Bullera alba PGY-2 represents an endophytic antagonistic yeast with promising biocontrol potential and alternative to the use of synthetic, chemical fungicides for the control of postharvest gray mold in apples.

Potential of Bacillus subtilis and Oregano Essential Oil in Controlling Postharvest Gray Mold Caused by Botrytis cinerea and Maintaining Quality Attributes of Sweet Cherry

Potential of Bacillus subtilis and Oregano Essential Oil in Controlling Postharvest Gray Mold Caused by Botrytis cinerea and Maintaining Quality Attributes of Sweet Cherry

Plumbagin controls fungal postharvest pathogens by affecting metabolism and inducing autophagy

Botrytis cinerea is a devastating postharvest pathogenic fungus causing severe postharvest decay in a wide range of fruit and vegetables. Controlling postharvest pathogens is essential to the postharvest industry. Plumbagin is a plant-derived naphthoquinone compound with various pharmacological activities, such as antioxidant, anti-inflammatory, and antimicrobial effects. However, its antifungal effects on B. cinerea have not been fully elucidated. In this study, we investigated the antifungal activity of plumbagin against postharvest fungal pathogens and elucidated its potential mechanism on B. cinerea through transcriptomics. Plumbagin exhibited broad-spectrum antifungal activity and completely inhibited the growth of various postharvest pathogens at a concentration of 20 mg L−1in vitro. Moreover, plumbagin effectively inhibited the incidence of gray mold in grape, sweet cherry, and strawberry fruit. The spore germination and viability of B. cinerea were also suppressed by plumbagin. Transcriptomic analysis indicated that plumbagin significantly affected the metabolic processes and induced autophagy in B. cinerea. Our results suggest that plumbagin is a promising broad-spectrum plant-derived fungicide that suppresses postharvest gray mold by affecting the metabolism of B. cinerea and inducing autophagy. These findings provide a theoretical basis for applying plumbagin to control postharvest pathogens.

Antifungal Activities of L-Methionine and L-Arginine Treatment In Vitro and In Vivo against Botrytis cinerea.

Gray mold caused by Botrytis cinerea is a common postharvest fungal disease in fruit and vegetables. The prevention and treatment of postharvest gray mold has been one of the hot research issues addressed by researchers. This study aimed to investigate the effect of L-methionine and L-arginine on Botrytis cinerea in vitro and on cherry tomato fruit. The results of the in vitro experiment showed that L-methionine and L-arginine had significant inhibitory effects on the mycelial growth and spore germination of Botrytis cinerea, and the inhibitory effects were enhanced with increasing L-methionine or L-arginine concentration. In addition, L-methionine and L-arginine treatment increased the leakage of Botrytis cinerea electrolytes, proteins and nucleic acids. The experiment involving propidium iodide staining and malondialdehyde content assay also confirmed that L-methionine and L-arginine treatment could lead to cell membrane rupture and lipid peroxidation. The results of scanning electron microscopy further verified that the morphology of hyphae was damaged, deformed, dented and wrinkled after treatment with L-methionine or L-arginine. Fruit inoculation experiments displayed that L-methionine and L-arginine treatments significantly inhibited the occurrence and development of gray mold in postharvest cherry tomato. Therefore, treatment with L-methionine or L-arginine might be an effective means to control postharvest gray mold in fruit and vegetables.

Application of Bacillus tequilensis for the control of gray mold caused by Botrytis cinerea in blueberry and mechanisms of action: inducing phenylpropanoid pathway metabolism.

Botrytis cinerea a blueberry gray mold, is one of the main diseases affecting postharvest storage, causing significant losses. Several studies have shown that Bacillus tequilensis can prevent the growth of plant pathogens by producing various antibacterial substances, and can induce plant resistance. However, research on the biological management of post-harvest gray mold in blueberries using B. tequilensis remains unclear. To better control the postharvest gray mold of blueberry, the effects of B. tequilensis KXF6501 fermentation solution (YY) and KXF6501 cell-free supernatant (SQ) on the induction of disease resistance in blueberry fruits were studied using biochemical and transcriptomic analyses. We found that YY controlled the conidial germination and mycelial growth of B. cinerea in vitro, followed by SQ. After 3 d of culture, the lesion diameter and incidence of gray mold in blueberry fruits inoculated with YY and SQ were smaller than those in the control group. Therefore, gray mold in blueberries was effectively controlled during the prevention period, and the control effect of YY was better than that of SQ. Transcription spectrum analysis of blueberry peel tissue showed that the YY- and SQ-induced phenylpropane metabolic pathways had more differentially expressed genes (DEGs) than other biological pathways. In addition, biochemical analyses showed that YY treatment effectively enhanced the activity of enzymes related to the phenylpropane pathway (phenylalanine ammonialyase [PAL], cinnamate 4-hydroxylase [C4H], 4-coumarate CoA ligase [4CL], and polyphenol oxidase [PPO]) and stimulated the synthesis of lignin, total phenols, and flavonoids, followed by SQ. Compared with the control, the YY and SQ treatments reduced the weight loss rate and better maintained the appearance and nutritional quality of the blueberry fruits. Our findings suggest that B. tequilensis KXF6501 is potentially useful as a suitable bio-control agent in harvested blueberries.

Effectiveness of Four Synthetic Fungicides in the Control of Post-Harvest Gray Mold of Strawberry and Analyses of Residues on Fruit

Fungicides are usually applied on strawberries to manage gray mold, induced by the fungal pathogen Botrytis cinerea. In this study, four reduced-risk fungicides (formulations of pyrimethanil, PYR, 175 mL/hL; boscalid, BOS, 80 g/hL; combination fludioxonil, FLU, +cyprodinil, CYP, 110 g/hL) were applied before harvest for the management of post-harvest diseases of strawberries. The resulting fungicide residues on the strawberry fruit were also quantified. Strawberry fruits were harvested at 0, 4, 8, and 12 days following treatment (dft) and kept at 20 ± 1 °C for 4 days or cold-stored for 7 days at 0.5 ± 1 °C, followed by a 4-day shelf life at 20 ± 1 °C. All fungicides significantly reduced gray mold, according to the McKinney Index. At 0 dft and 4 days of shelf life, the FLU + CYP completely prevented post-harvest strawberry gray mold, while PYR and BOS reduced the disease by 88% and 42%, respectively, in comparison to the untreated control. For the duration of experiment, fungicide residues were always below the maximum residue levels, and FLU was the most degraded, thanks to the enzymatic pool of the strawberries. Monitoring fungicide residues in strawberries is essential to provide the consumer information on the safety of this widely consumed fruit. The present study points out the safety of strawberry fruits for consumers, even if the treatment strategy implies the use of fungicide mixtures before the consumption, with fungicide levels always being below the MRL.

Isolation, Morphological Characterization, and Phylogenetic Identification of Botrytis cinerea Associated with Postharvest Gray Mold of Apple Fruits

Isolation, Morphological Characterization, and Phylogenetic Identification of Botrytis cinerea Associated with Postharvest Gray Mold of Apple Fruits

EFFECTIVENESS OF 7S GLOBULIN AGAINST BOTRYTIS CINEREA CAUSING GRAY MOLD IN STRAWBERRY

Gray mold caused by Botrytis cinerea is the most harmful postharvest disease responsible for the degradation of strawberries. The presented study targeted the preparation of 7S globulin from pea seeds to serve as an antifungal agent against B. cinerea in vitro and on the post-harvest strawberry to extend the fruits’ shelf life. The 7S globulin isolation from pea seeds and characterization employed various methods, such as SDS-PAGE, FTIR, and pH solubility curve. The molecular technique also helped confirm the identity of the causative microorganism of the gray mold disease in strawberries. Utilizing rRNA gene sequencing identified a fungal pathogen that causes gray mold as B. cinerea. The 7S globulin showed three protein bands corresponding to α/ (83 KDa), α (68 KDa), and β (60 KDa) subunits. The isoelectric point was notable at pH 5.8. The essential and non-essential amino acids occurred around 24.92% and 54.04%, respectively. The 7S globulin inhibited the mycelial growth of B. cinerea in a concentration-dependent manner. The Scanning Electron Microscope (SEM) of B. cinerea subjected to 7S globulin showed swelling of both the fungal hyphae and conidia, significantly affected by the pea 7S-globulin treatment, entirely destabilizing and deforming their shape at 0.4 g/L. The 7S-globulin exposure maintained the fruit quality and stopped the strawberry’s natural deterioration. Results further authenticated that 7S globulin (isolated from pea seeds) revealed effective antifungal action against B. cinerea mycelial development via a membrane-targeted mechanism. The 7S globulin affects hyphal morphology, compromises plasma membrane integrity, and prevents post-harvest gray mold on strawberry fruits.

Cinnamaldehyde Inhibits Postharvest Gray Mold on Pepper Fruits via Inhibiting Fungal Growth and Triggering Fruit Defense.

Gray mold infected with Botrytis cinerea frequently appears on fruits and vegetables throughout the supply chain after harvest, leading to economic losses. Biological control of postharvest disease with phytochemicals is a promising approach. CA (cinnamaldehyde) is a natural phytochemical with medicinal and antimicrobial activity. This study evaluated the effect of CA in controlling B. cinerea on fresh pepper fruit. CA inhibited B. cinerea growth in vitro significantly in a dose- (0.1-0.8 mM) and time-dependent (6-48 h) manner, with an EC50 (median effective concentration) of 0.5 mM. CA induced the collapse and breakdown of the mycelia. CA induced lipid peroxidation resulting from ROS (reactive oxygen species) accumulation in mycelia, further leading to cell leakage, evidenced by increased conductivity in mycelia. CA induced mycelial glycerol accumulation, resulting in osmotic stress possibly. CA inhibited sporulation and spore germination resulting from ROS accumulation and cell death observed in spores. Spraying CA at 0.5 mM induced a defense response in fresh pepper fruits, such as the accumulation of defense metabolites (flavonoid and total phenols) and an increase in the activity of defense enzymes (PAL, phenylalanine ammonia lyase; PPO, polyphenol oxidase; POD, peroxidase). As CA is a type of environmentally friendly compound, this study provides significant data on the activity of CA in the biocontrol of postharvest gray mold in peppers.

Postharvest preservation effect of composite biocontrol agent on tomatoes

Biological control has been highly sought after as an effective means of controlling postharvest diseases in tomatoes. In order to explore effective biocontrol bacteria for postharvest biological control, this experiment isolated and screened 3 bacterial strains with potential for biocontrol. These 3 strains were Bacillus velezebsis (WZ-37), Bacillus subtilis subsp.subtilis (WXCDD105), and Bacillus amyloliquefaciens (SS). The enhancer for different biocontrol bacteria were also screened, and the effectiveness of composite biocontrol agents was evaluated. The results showed that these strains had a good inhibitory effect on the occurrence of tomato postharvest gray mold disease, significantly reducing the disease incidence rate while enhancing fruit quality and preservation. Among them, WZ-37 showed the most outstanding biocontrol effect, while the composite biocontrol effect of SS+WZ-37 was the best. Each strain has its corresponding optimal enhancer, and the addition of enhancer can increase the concentration of biocontrol bacteria and improve the biocontrol effect. In this study, three synergists, 0.01% B1, 0.01% Thr, and 0.01% Met, were screened to have the best effect on our strains. After spraying the biocontrol agents, the water loss rate of the postharvest fruits was significantly decreased, and a biofilm formed on the surface of tomatoes effectively reduced the occurrence of diseases. Therefore, these strains have high applied value and promotional prospects, and can be used for postharvest disease biological control of tomato.

Biofumigation by Mustard Plants as an Application for Controlling Postharvest Gray Mold in Apple Fruits

Gray mold caused by Botrytis cinerea is a critical disease that results in severe postharvest losses for the apple industry. In recent years, biological control has become an increasingly effective approach for controlling postharvest diseases in fruits. Brassica plants contain abundant natural compounds with known antimicrobial activity against numerous plant pathogens. In this study, a large-scale screening of 90 mustard cultivars was conducted to evaluate their biofumigation effects against B. cinerea. Among these, one mustard cultivar named Dilong-1, displayed the highest inhibitory effect against B. cinerea, and was able to completely inhibit mycelial growth. Further investigations showed that fumigation with Dilong-1 inhibited mycelial growth, sporulation, and spore germination of B. cinerea in vitro. In addition, fumigation using Dilong-1 showed a wide antifungal spectrum, including other fruit postharvest pathogens such as Phytophthora litchii. Furthermore, apple gray mold disease severity was significantly reduced by biofumigation using Dilong-1. Importantly, fumigation with Dilong-1 did not negatively impact final apple qualities, including weight loss, firmness, and total soluble solids. These results suggested that Dilong-1 significantly inhibited gray mold decay caused by B. cinerea without affecting the quality of apple fruits. In conclusion, biological fumigation of apple fruits with the mustard cultivar Dilong-1 is a promising eco-friendly approach for controlling apple gray mold during storage and shipment.

Isolation, structural characterization and sporicidal properties of Baelezcin A, a novel cyclic lipopeptide from Bacillus velezensis SJ100083 against gray mold.

Postharvest gray mold induced by Botrytis cinerea seriously affects cherry quality, resulting in huge economic losses. The aim of this study was to isolate and purify a novel antifungal compound from the endophytic Bacillus velezensis SJ100083 of cherries to prevent postharvest gray mold. In this study, Baelezcin A, extracted and purified from Bacillus velezensis SJ100083, was found effective in suppressing gray mold on cherries. Furthermore, the structure of Baelezcin A was identified as a novel cyclic lipopeptide with molecular formula of C52 H91 N7 O13 through ultra-high-performance liquid chromatography quadrupole Orbitrap high-resolution mass spectrometry (UHPLC-Q-Orbitrap-HRMS) and nuclear magnetic resonance (NMR). Baelezcin A treatment at 25 mg L-1 significantly decreased the disease incidence and severity of cherry gray mold, the antifungal mechanism of which was attributed to the accumulation of reactive oxygen species within the spores and the leakage of mycelium cytoplasmal contents, resulting in a low rate of spore germination. Moreover, it was proven to be biologically safe within a certain range by MTT assays. Our study demonstrated that Baelezcin A from the culture of Bacillus velezensis SJ100083 may be a promising fruit preservative for controlling postharvest gray mold caused by Botrytis cinerea. © 2023 Society of Chemical Industry.

Biocontrol ability and action mechanism of Bacillus amyloliquefaciens Baf1 against Fusarium incarnatum causing fruit rot in postharvest muskmelon (cv. Yugu) fruit

Muskmelon (Cucumis melo L. cv. Yugu) is favoured by consumers for its high quality, attractive appearance, and good palatability. However, fruit rot is a prominent threat during postharvest storage, resulting in potentially substantial serious losses. In this study, we investigated the biocontrol efficacy of Bacillus amyloliquefaciens Baf1 against fruit rot caused by Fusarium incarnatum in post-harvest Yugu muskmelon, and examined the underlying antagonistic mechanisms. Baf1 had more than 75% control effect on F. incarnatum in vitro and in vivo. In addition, Baf1 treatment effectively improved the fruit defense enzyme activities (PAL, POD, and PPO) and maintained the quality (weight loss, respiration rate, ascorbic acid and total soluble solid) of muskmelon during storage. A 5 mL/L lipopeptide extracted from Baf1 inhibited the hypha growth and conidia germination and production of F. incarnatum by 55%, 63.2%, and 65%, respectively, and caused hyphal malformation. The active antifungal substances of Baf1 were preliminarily identified as C13–C15 surfactins and C17 bacillomycin L based on matrix-assisted laser desorption ionization time-of-flight mass spectrometry. Thus, the biocontrol agent Baf1 showed great potential for inhibiting postharvest grey mould in muskmelons and could be a useful approach for enhancing the quality and storability of muskmelons.

Combining the biocontrol agent Meyerozyma guilliermondii with UV-C treatment to manage postharvest gray mold on kiwifruit

Biological and physical controls as eco-friendly methods are being pursued actively to manage postharvest diseases. Postharvest gray mold is one of the major causes of significant economic losses for kiwifruit industry. Effects of the biocontrol yeast Meyerozyma guilliermondii and UV-C to control gray mold and natural infection on kiwifruit were determined in this study. M. guilliermondii or UV-C as an individual treatment inhibited gray mold and natural infection development. The combined treatment of M. guilliermondii and UV-C provided greater control efficacy than each individual treatment. The growth of M. guilliermondii in fruit wounds was not negatively impacted by UV-C. The analysis at the molecular and physiological levels showed that M. guilliermondii and UV-C alone or in combination induced defensive gene expression and total phenolics in kiwifruit. The disease resistance response induced by UV-C may partially contribute to enhancement in the biocontrol effectiveness of M. guilliermondii on kiwifruit. Taken together, these findings suggested that the hurdle technology combining biocontrol and physical controls may represent a promising method to manage gray mold on kiwifruit.

Antifungal activity of Bacillus mojavensis D50 against Botrytis cinerea causing postharvest gray mold of tomato

Botrytis cinerea causes considerable economic losses to the tomato processing industry. Hence, the study evaluated the antifungal activity of eight biocontrol strains isolated from tomato rhizosphere soil against B. cinerea. These strains demonstrated potent antifungal activity with an inhibition rate ranging from 19.30% to 69.88%. Among them, a strain named D50 showed the highest effect with an inhibition rate of 69.88%. D50 strain was identified as Bacillus mojavensis by morphological, physiological, and biochemical analyses. The Bacillus mojavensis D50 fermentation supernatant (BMFS) was used for subsequent experiments to unveil antimicrobial activity of its secondary metabolites. BMFS (5%, v/v) reduced the growth of B. cinerea by inhibiting mycelial growth, conidial production, and mycelial dry weight by 51.7%, 45.9%, and 53.7%, respectively. Detailed analysis revealed that the antifungal effect of BMFS decreased when it was heated above 80 °C and adjusted to pH 2, 8, and 10. The antifungal effect also decreased when exposed to UV for more than 40 min. Further, the in vivo effect of BMFS in preventing gray mold was evaluated using cherry tomatoes. After B. cinerea inoculation for 5 days, the disease incidence and disease severity of cherry tomato treated with BMFS decreased by 33.5% and 31.5%, respectively. BMFS treatment enhanced the activities of peroxidase (POD), catalase (CAT), polyphenol oxidase (PPO), superoxide dismutase (SOD), and phenyl alanine lyase (PAL) and increased the content of malondialdehyde (MDA) in cherry tomatoes during infection. Moreover, BMFS prevented tomato gray mold by enhancing the transcript levels of systemic acquired resistance-related marker genes (SlLoxD, SlMyc2, SlPR1-a, SlPAL5, SlEIN2, and SlEIN3). SlLoxD and SlMyc2 had high expression levels among the defense-related genes, indicating activation of the jasmonic acid signal pathway. Thus, the study demonstrates the great potential of BMFS in managing the postharvest gray mold of tomato caused by B. cinerea.

Antifungal activity of diacetyl, a volatile organic compound, on Trichoderma lixii F2 isolated from postharvest Lanzhou lily bulbs

The most severe fungal disease is postharvest gray mold, which might cause massive losses in Lanzhou lily bulbs. Some microorganism-produced volatile organic compounds (VOCs) have been proven to have antifungal action and can be employed as fruit and vegetable preservation. Our most recent research discovered that diacetyl (2, 3-butanedione) produced by Bacillus subtilis CL2 could significantly prevent some pathogens. The goal of this investigation was to see if diacetyl had antifungal properties against Trichoderma lixii F2, one of the most common postharvest rot pathogens of Lanzhou lily bulbs. The results indicated that diacetyl (1.587 μL/mL) fumigation treatment significantly inhibited the hyphal growth, modified hyphal morphology, and disrupted the cell membrane integrity. In vivo tests the antifungal mechanisms of diacetyl on T. lixii F2 were performed in Lanzhou lily bulbs. The results indicated that the content of total phenols and flavonoids increased, while malondialdehyde decreased under different treatment by diacetyl. Meanwhile, the activities of peroxidase, polyphenol oxidase, catalase, and superoxide dismutase and phenylalanine ammonia-lyase in Lanzhou lily bulbs were investigated. It was showed that diacetyl could eliminate excessive reactive oxygen species, reduce the damage of plant cells, and improve the resistance of Lanzhou lily bulbs against T. lixii F2. This research reveals that diacetyl could activate antioxidant enzymes and disease-resistant enzymes in Lanzhou lily bulbs to prevent pathogenic fungus from invading and inducing resistance, laying the groundwork for future uses in preserving Lanzhou lily bulbs.