Antifungal Activity Of Volatile Compounds Research Articles

Unravelling the modes of action of autochthonous staphylococci against Aspergillus westerdijkiae and the antiochratoxigenic effect in dry-cured ham

Aspergillus westerdijkiae is well known for its capacity to produce high amounts of ochratoxin A (OTA) in dry-cured ham. Some autochthonous microorganisms, such as Staphylococcus xylosus FHSCC Sx8 and Staphylococcus equorum FHSCC Se31 have antifungal effect and can be used as biocontrol agents (BCAs) to reduce the OTA contamination. The aims of this work were to reveal their modes of action against A. westerdijkiae MUM 16.142 in a dry-cured ham model system and validate the antifungal effect in dry-cured ham. As well as to assess the effect of live cells, dead cells, and cell-free broth; the pattern of nutrient use, the niche overlap index (NOI), interactions by dual culture assays, the antifungal activity of volatile compounds, and their effect on the fungal proteome. Both cocci in the dual-culture assay were able to decrease the A. westerdijkiae growth, but only S. xylosus reduced the OTA production at 20 °C. Moreover, changes in the abundance of proteins related to cell wall integrity, secondary metabolite production and carbohydrate metabolism were observed. Furthermore, the anti-A. westerdijkiae effect of S. xylosus was validated in dry-cured ham since this coccus was able to reduce the OTA production in this meat product.

Antifungal activity of volatile compounds from Bacillus tequilensis XK29 against Botrytis cinerea causing gray mold on cherry tomatoes

Botrytis cinerea is a necrotrophic fungal pathogen that causes gray mold disease in more than 1400 plant species. The biocontrol effect of microbial volatile compounds on postharvest diseases has become a research hotspot. This study revealed the biocontrol effects of volatiles released by Bacillus tequilensis XK29 on B. cinerea in vitro and in vivo. The results showed that the strain XK29 volatiles inhibited the mycelial growth of B. cinerea. The inhibition effect of strain XK29 volatiles against B. cinerea was increased by optimizing the wheat seeds weight, suspension concentration and inoculation volume of strain XK29, and the pre-culture time. The volatiles of strain XK29 affected the mycelial development, the formation of conidia, and the metabolic activity of B. cinerea. Selected individual monomers and artificial mixtures showed strong antifungal activity against B. cinerea. The volatiles of strain XK29 reduced the lesion diameter and disease severity of cherry tomatoes after inoculation with B. cinerea. These results indicate that the fumigation with B. tequilensis XK29 volatiles is a promising approach to protect cherry tomatoes from gray mold disease. This is also the first study to prove the antifungal effect of B. tequilensis on B. cinerea and its biocontrol effect on postharvest cherry tomatoes.

First Report on Post-harvest management of black mold of onion by eugenol

Black mold of onion caused by Aspergillus niger is a serious and prevalent postharvest disease of onion. This problem drastically reduces the quality and marketability of onion bulbs. Conventional fungicides employed to con-trol A. niger contamination posed negative impact on human health and en-vironment and highlighted the need to discover ecofriendly management practices. In the present study we attempted to explore the use of eugenol for the management of black mold of onion. Eugenol may exhibit differ-ences in antifungal activity in liquid state and in volatile phase. Hence, we developed and validated a new method, conical flask- paper cone method to study the antifungal activity of vapour phase disinfectants. This method was found to be precise, reproducible, sensitive and accurate with inter-assay R.S.D < 10%, intra-assay R.S.D <5% and R2>0.99. Conical flask- paper cone method was further utilized to determine the minimum inhibitory concen-tration of eugenol against A. niger. We observed that 0.03355 μl / cm3 eu-genol caused invitro and invivo inhibition of A. niger. Onion bulbs that were stored by eugenol fumigation, prior inoculated by A. niger, did not develop black mold symptoms and maintained high sensory acceptability. Microscop-ic observations revealed that eugenol fumigation resulted in inhibition of spore germination, coagulation of cytoplasm, formation of large vesicles and shrinkage of A. niger mycelium. In conclusion, our study showed for the first time that eugenol fumigation significantly controlled black mold incidence during storage and maintained post harvest quality and sensory acceptance. This study also introduced a new method for evaluating antifungal activity of volatile compounds.

Antifungal activity of volatile compounds generated by endophytic fungi Sarocladium brachiariae HND5 against Fusarium oxysporum f. sp. cubense.

The soil-born filamentous fungal pathogen Fusarium oxysporum f. sp. cubense (FOC), which causes vascular wilt disease in banana plants, is one of the most economically important Fusarium species. Biocontrol using endophytic microorganisms is among the most effective methods for controlling banana Fusarium wilt. In this study, volatile organic compounds (VOCs) showed strong antifungal activity against FOC. Seventeen compounds were identified from the VOCs produced by endophytic fungi Sarocladium brachiariae HND5, and three (2-methoxy-4-vinylphenol, 3,4-dimethoxystyrol and caryophyllene) showed antifungal activity against FOC with 50% effective concentrations of 36, 60 and 2900 μL/L headspace, respectively. Transmission electron microscopy (TEM) and double fluorescence staining revealed that 2-methoxy-4-vinylphenol and 3,4-dimethoxystyrol damaged the plasma membranes, resulting in cell death. 3,4-dimethoxystyrol also could induce expression of chitin synthases genes and altered the cell walls of FOC hyphae. Dichloro-dihydro-fluorescein diacetate staining indicated the caryophyllene induced accumulation of reactive oxygen species (ROS) in FOC hyphae. FOC secondary metabolism also responded to active VOC challenge by producing less fusaric acid and expressions of genes related to fusaric acid production were interrupted at sublethal concentrations. These findings indicate the potential of S. brachiariae HND5 as a biocontrol agent against FOC and the antifungal VOCs as fumigants.

Potential of Octanol and Octanal from Heracleum sosnowskyi Fruits for the Control of Fusarium oxysporum f. sp. lycopersici

The antifungal activity of volatile compounds from the fruit, leaf, rhizome and root of 109 plant species was evaluated against Fusarium oxysporum f. sp. lycopersici (FOL) race 1—the tomato wilt pathogen—by using the modified dish pack method. Eighty-eight plant samples inhibited mycelial growth, including volatiles from fruits of Heracleum sosnowskyi, which exhibited the strongest antifungal activity, showing 67% inhibition. Two volatile compounds from the fruits of H. sosnowskyi (octanol and octanal) and trans-2-hexenal as a control were tested for their antifungal activities against FOL race 1 and race 2. In terms of half-maximal effective concentration (EC50) values, octanol was found to be the most inhibitory compound for both pathogenic races, with the smallest EC50 values of 8.1 and 9.3 ng/mL for race 1 and race 2, respectively. In the biofumigation experiment, the lowest disease severity of tomato plants and smallest conidial population of race 1 and race 2 were found in trans-2-hexenal and octanol treated soil, while octanal had an inhibitory effect only on race 2. Therefore, our study demonstrated the effectiveness of volatile octanol and trans-2-hexenal on the control of the mycelial growth of two races of Fusarium oxysporum f. sp. lycopersici and may have potential for the future development of novel biofumigants.

Antifungal activity of volatile compounds produced by endophytic Bacillus subtilis DZSY21 against Curvularia lunata

PurposeTo screen endophytic Bacillus producing volatile organic compounds (VOCs) with antifungal activity, and to explore their biocontrol properties toward the growth and pathogenicity of Curvularia lunata.MethodsTwo-sealed-base-plate assays were used to estimate the antifungal activities of Bacillus strains against C. lunata. Conjoint analysis of solid-phase microextraction gas chromatography-mass spectrometry and antagonistic experiments were used to identify the VOCs responsible for the antifungal activity. Effects of individual synthetic VOCs were analyzed along with reactive oxygen species (ROS) accumulation in C. lunata conidia. After exposure to individual VOCs, conidia were also sprayed onto maize leaves to evaluate their pathogenicity. Expression levels of virulence-related genes in C. lunata mycelium following exposure to VOCs were analyzed using quantitative real-time PCR.ResultsAmong the ten endophytic Bacillus strains and two plant growth-promoting rhizobacterial (PGPR) strains, only B. subtilis strain DZSY21 strongly inhibited the growth of C. lunata by producing VOCs. 2-Methylbutyric acid, 2-heptanone, and isopentyl acetate produced by strain DZSY21 showed inhibitory effects on the mycelia growth and conidial sporulation of C. lunata. 2-Heptanone and isopentyl acetate also repressed the germination of conidia and the expression levels of virulence-related genes in C. lunata mycelium. Moreover, isopentyl acetate strongly enhanced the accumulation of intracellular ROS in conidia. The disease indexes of maize leaves sprayed with VOC-treated C. lunata conidia were reduced from 60.52 to 26.64%.ConclusionEndophytic B. subtilis strain DZSY21 displayed the potential to control C. lunata by producing VOCs, especially 2-heptanone and isopentyl acetate.

Antifungal activity of volatile compounds produced by Staphylococcus sciuri strain MarR44 and its potential for the biocontrol of Colletotrichum nymphaeae, causal agent strawberry anthracnose

A nonpathogenic endophytic bacterial isolate, recovered from Fragaria × ananassa stolon, and its antifungal activity against Colletotrichum nymphaeae was evaluated under in vitro, in vivo, and greenhouse conditions. Bacterial isolate was identified as Staphylococcus sciuri MarR44 (Strain ID: WDCM 891 = CCSM-B 00640) using phenotypic and biochemical properties and molecular phylogenetic analysis of the 16S rDNA gene sequences. The living cells of strain MarR44 inhibited mycelial growth of C. nymphaeae (52.46%) using dual-culture method. The volatile compounds (VOCs) produced by MarR44 inhibited mycelial growth and conidial germination of C. nymphaeae by 34.52% and 82.81%, respectively. However, inhibition percentage of mycelial growth of pathogen by culture filtrates of the strain MarR44 was lower (23.07%) than that for the two dual culture and volatile compounds assay tests. Moreover, the cell-free-culture filtrates of this strain reduced the biomass and conidial germination of pathogen by 91.89% and 41.10%, respectively. Also, the strain MarR44 was capable of producing protease, chitinase, HCN, siderophore, IAA, gibberellin, and biofilm. The living cells and volatile compounds of the strain MarR44 reduced anthracnose disease at post-harvest on fruit by 52.45% and 72.17%, respectively. Furthermore, disease severity of strawberry anthracnose was reduced using drenching soil and inoculated plants methods by 77.77 and 72.22%, respectively, 60 days after inoculation. The VOCs released by strain MarR44 were analyzed by Gas chromatography-mass spectroscopy (GC–MS). Out of 24 identified VOCs, Mesityl oxide (81.436%), Acetic acid, 2-methylpropyl ester (3.442%), 4-Methyldecane (1.837%), 4-Penten-2-one,4-methyl- (1.739%), Toluene (1.248%), and o-Xylene (1.24%) were the major components. The mode of action of S. sciuri MarR44 on the C. nymphaeae was through the production of antifungal volatile compounds (Antibiosis), which inhibited mycelial growth and conidial germination of pathogen in vitro and fruit decay development in vivo. To the best of our knowledge, this is the first report of S. sciuri having antifungal activity against causal agent strawberry anthracnose. These results indicated that the VOCs of S. sciuri strain MarR44 are promising biofumigant for management of strawberry anthracnose.

Variability and antifungal activity of volatile compounds from Aniba rosaeodora Ducke, harvested from Central Amazonia in two different seasons

Finding new applications for the essential oils (EOs) of the branches and leaves of Aniba species represents a valuable strategy for the adoption of correct management of the crown and to help make Aniba plantations economically valuable. We report here the antifungal activity of the EO from Aniba rosaeodora Ducke against plant pathogenic fungi. The present study investigated the chemical variability and antifungal effect of EO from A. rosaeodora harvested during the wet and dry seasons in the Amazon region. The volatile content obtained from the aerial parts by hydro-distillation was analyzed for its chemical composition by gas chromatography–mass spectrometry (GC–MS). Furthermore, a broth and agar dilution method was used to determine the antifungal activity against phytopathogens. Quantitative and qualitative variations in composition among the EOs were detected. Linalool was a major component in the oil of leaves and branches from both periods. Quantification using an external standard showed a higher concentration of linalool in the wet season (74.4 ± 3.9% in leaves and 81.8 ± 5.7% in branches) than in the dry season (47.5 ± 2.2 in leaves and 49.2 ± 1.6% in branches). The EOs were toxic to all phytopathogens analyzed, displaying superior inhibitory activity toward Colletotrichum guaranicola, with inhibition zone diameters ranging from 15.2 ± 1.2 to 21.3 ± 1.7 mm and IC50 values of 0.578 to 2.094 μL mL−1. Interestingly, the EOs collected during the wet season were effective in reducing the vegetative growth of phytopathogens, providing evidence for the involvement of linalool in the inhibitory effect.

Antifungal Activity of Volatile Compounds Produced by an Edible Mushroom Hypsizygus marmoreus against Phytopathogenic Fungi

AbstractVolatile compounds with antifungal activity produced by edible mushrooms have potential as biological control agents to combat fungal diseases and reduce fungicide use in agriculture. Here we investigated the antifungal activity of volatile compounds produced by the edible mushroom Hypsizygus marmoreus (TUFC 11906) against eight phytopathogenic fungi. The results showed that volatile compounds from the mycelia and culture filtrates (CFs) of H. marmoreus had antifungal activity against some phytopathogenic fungi. Among them, the mycelial growth and conidial germination of Alternaria brassicicola were significantly inhibited by 60 and 100%, respectively. Moreover, the volatile compounds from CFs inhibited the lesion formation of A. brassicicola on detached cabbage leaves by 94%. The volatile compounds had higher antifungal activity against A. brassicicola than other fungi. With the removal of the volatile compounds from conidia of A. brassicicola, the conidia began to germinate, which indicates fungistatic activity of the compounds. The volatile compounds were isolated from the CFs of H. marmoreus, and the major volatile compound with antifungal activity was estimated to be 2‐methylpropanoic acid 2,2‐dimethyl‐1‐(2‐hydroxy‐1‐methylethyl)propyl ester. As the volatile compound produced by H. marmoreus is a product of an edible mushroom and has fungistatic activity against some phytopathogenic fungi, especially A. brassicicola, it may be possible to use the compounds as a novel safe agent for protecting crops in the field and during storage.

Biocontrol potential of Trichoderma species against mango malformation pathogens

Malformation disease of Mango (Mangifera indica L.) caused by Fusarium moniliforme var. subglutinans is one of the most destructive diseases, which is a major production constraint in the mango-growing regions of India. In this study, The bioagents Trichoderma viride (Tr1), Trichoderma virens (Tr2) and Trichoderma harzianum (Tr3) were evaluated in culture with the pathogens to monitor the antagonistic effect and their volatile compound and culture filtrates (non-volatile compound). It was found that all the three isolates of bioagents significantly checked the growth of F. moniliforme var. subglutinans. In dual culture, the best result was obtained with T. harzianum followed by T. virens and T. viride. A similar result was also observed in the case of culture filtrates ofTrichoderma spp. The results clearly showed that inhibition of the growth of the fusaria isolates by T. harzianum was significantly superior to T. viride andT.virens. In case of antifungal activity of volatile compounds released by Trichoderma isolates, it was also observed that T. virens was more superior to T.harzianum and T. viride.

Antifungal activity of volatile compounds generated by essential oils against fungi commonly causing deterioration of bakery products.

To investigate the volatile fractions of 16 essential oils for activity against the more common fungi causing spoilage of bakery products, Eurotium amstelodami, E. herbariorum, E. repens, E. rubrum, Aspergillus flavus, A. niger and Penicillium corylophilum. The study applied 50 microl of pure essential oils in a sterilized filter paper, were carried out at pH 6 and at different water activity levels (0.80-0.90). First, a wheat flour based agar medium was used, where cinnamon leaf, clove, bay, lemongrass and thyme essential oils where found to totally inhibit all microorganisms tested. These five essential oils were then tested in sponge cake analogues, but the antifungal activity detected was much more limited. Five essential oils showed potential antifungal capacity against all species tested, over a wide range of water availability. Their activity, however, seems to be substrate-dependent. More research is needed to make them work in real bakery products, as in the preliminary study limited effectiveness was found. The potential of the cinnamon leaf, clove, bay, lemongrass and thyme essential oils against species belonging to Eurotium, Aspergillus and Penicillium genus has been demonstrated.

Automatic evaluation of antifungal volatile compounds on the basis of the dynamic growth process of a single hypha

An automatic analysing system was developed and employed for the evaluation of antifungal activity of volatile compounds in the gas phase. Aspergillus niger was inoculated on agar medium in the reaction vessel. The reaction vessel was incubated at 28 degrees C for 24 h and then a volatile compound was introduced into the vessel either in a batch or flow manner. The antifungal activity of the respective compounds estimated in situ was expressed by the dynamic response parameters of a single hypha. All volatiles tested in the present system inhibited hyphal growth, except linalyl acetate: Limone and geraniol were the most inhibitory. In contrast, linalyl acetate promoted hyphal growth. By definition of the parameters, the fungicidal and fungistatic effects could be distinguished.

Automatic antifungal activity analyzing system on the basis of dynamic growth process of a single hypha.

A system for the evaluation of antifungal activity of volatile compounds has been developed that is based on dynamic growth of a single hypha. The newly developed system is composed of a reaction vessel under a microscope, automatic stage, charge coupled device (CCD) camera, TV monitor, video tape recorder (VTR), and a microcomputer. A fungus was inoculated in the reaction vessel containing agar medium and then was treated with an antifungal reagent in the gas phase either in batch or flow reaction manner. The apex of a growing hypha displayed on a TV monitor was followed automatically. From the ratio of the growth rate under exposure of a reagent (UEXPO) to the growth rate before the exposure (UPRE), the antifungal activity was expressed quantitatively.