Search Results (38)

The major objective was to investigate the protective capabilities of endophytic bacterial strains isolated from a number of medicinal plant species towards Aspergillus spp. secured from the internal tissues of fungi-infected peanuts. Among 32 fungal isolates surveyed for mycotoxin production in various culture media (PDA, RBCA, YES, CA), 10 isolates qualitatively producing AFB₁, besides 10 OTA-producers, were assayed by HPLC for quantitative toxin production. Aspergillus spp. isolate Be 13 produced an extraordinary quantity of 1859.18 μg mL⁻¹ AFB₁, against the lowest toxin level of 280.40 μg mL⁻¹ produced by the fungus isolate IS 4. The estimated amounts of OTA were considerably lower and fell in the range 0.88–6.00 μg mL⁻¹; isolate Sa 1 was superior, while isolate Be 7 seemed inferior. Based on ITS gene sequencing, the highly toxigenic Aspergillus spp. isolates Be 13 and Sa 1 matched the description of A. novoparasiticus and A. ochraceus, respectively, ochraceus, respectively, which are present in GenBank with identity exceeding 99%. According to 16S rRNA gene sequencing, these antagonists labeled Ar6, Ma27 and So34 showed the typical characteristics of Pseudomonas aeruginosa, Bacillus subtilis and Bacillus velezensis, respectively, with similarity percentages of 99–100. The plant growth-promoting activity measurements of the identified endophytes indicated the production of 16.96–80.00 μg/100 mL culture medium of IAA. Phosphate-solubilizing capacity varied among endophytes from 2.50 to 21.38 μg/100 mL. The polysaccharide production pool of bacterial strains ranged between 2.74 and 6.57 mg mL⁻¹. P. aeruginosa Ar6 and B. velezensis successfully produced HCN, but B. subtilis failed. The in vitro mycotoxin biodegradation potential of tested bacterial endophytes indicated the superiority of B. velezensis in degrading both mycotoxins (AFB₁-OTA) with average percentage of 88.7; B. subtilis ranked thereafter (85.6%). The 30-day old peanut (cv. Giza 6) seedlings grown in gnotobiotic system severely injured due to infection with AFB₁/OTA-producing fungi, an effect expressed in significant reductions in shoot and root growth traits. Simultaneous treatment with the endophytic antagonists greatly diminished the harmful impact of the pathogens; B. velezensis was the pioneer, not P. aeruginosa Ar6. In conclusion, these findings proved that several endophytic bacterial species have the potential as alternative tools to chemical fungicides for protecting agricultural commodities against mycotoxin-producing fungi. Full article

Mycotoxin contamination of food and feed is a worldwide problem that needs to be addressed with highly efficient and biologically safe techniques. RNA interference (RNAi) is a natural mechanism playing an important role in different processes in eukaryotes, including the regulation of gene expression, maintenance of genome stability, protection against viruses and others. Recently, RNAi-based techniques have been widely applied for the purposes of food safety and management of plant diseases, including those caused by mycotoxin-producing fungi. In this review, we summarize the current state-of-the-art RNAi-based approaches for reducing the aggressiveness of key toxigenic fungal pathogens and mycotoxin contamination of grain and its products. The ways of improving RNAi efficiency for plant protection and future perspectives of this technique, including progress in methods of double-stranded RNA production and its delivery to the target cells, are also discussed. Full article

All major ear rots (F. graminearum, F. verticillioides, and Aspergillus flavus) and their toxins are present in maize of preharvest origin in Hungary. Resistance can be an important tool in reducing the infection and toxin contamination from these rots in maize. Previous results identified resistance differences in maize hybrids that were suitable for use in evaluating their risk from toxigenic fungi and their toxins. During the tests, two methodical improvements were achieved: the use of three isolates of the fungus secured and a more precise estimation of resistance to ear rots and their resistance to toxin accumulation or overproduction. The improvement in sampling and the tests of subsamples made the evaluation for the statistics much more exact. This way, we were able to reduce the Within value, providing a statistically more reliable method of evaluation. Earlier data had confirmed that toxin contamination could not be predicted well from visual ear rot severity data. Contradictory results for hybrid ranking were often identified between isolates. The resistance to disease and toxin contamination is not generally valid. The new suggested methodology compares the performance of hybrids in a large number of epidemic situations to identify adaptable hybrids that can respond to diverse conditions; therefore, the stability of resistance and toxin response is decisive information to evaluate risk analyses. The increased number of disease toxin data allowed for lower LSD 5% values for toxins, a much finer analysis of toxin overproduction and underproduction, and a wider database for stability analyses. This way, we obtained important additional separated information about resistance to accumulation of toxins and about maize resistance to these pathogens that is suitable to provide much more reliable testing than was possible until now. Globally, about 50–100 million metric tons can be saved by excluding susceptible hybrids from commercial production. Full article

Propolis is a naturally occurring substance with beneficial properties; bees produce it from various plant sources, and it is an anti-inflammatory and therapeutic resinous substance. This study aimed to enhance the biological features of propolis extract by loading it onto active film. Firstly, extraction was performed using three solvent systems, and their total phenolic, flavonoid, and antioxidant activity was measured. Propolis ethanol extract (EEP) was evaluated for phenolic fraction content and then chosen to prepare a chitosan-loaded emulsion with several concentrations. The antibacterial, anti-mycotic, and anti-mycotoxigenic properties of the extract and nanoemulsion were assessed. PPE’s cytotoxicity and nanoemulsion were evaluated using brine shrimp and cell line assays. Results indicate higher phenolic (322.57 ± 4.28 mg GAE/g DW), flavonoid (257.64 ± 5.27 mg QE/g DW), and antioxidant activity of the EEP. The phenolic fraction is distinguished by 18 phenolic acids with high p-hydroxybenzoic content (171.75 ± 1.64 µg/g) and 12 flavonoid compounds with high pinocembrin and quercetin content (695.91 ± 1.76 and 532.35 ± 1.88 µg/g, respectively). Phenolic acid derivatives (3,4-Dihydroxybenzaldehyde, 3,4-Dihydroxyphenol acetate, and di-methoxy cinnamic) are also found. Concentrations of 50, 100, 150, and 200 ng EEP loaded on chitosan nanoemulsion reflect significant antibacterial activity against pathogenic bacteria, particularly methicillin-resistant Staphylococcus aureus (MRSA) and toxigenic fungi, particularly Fusarium. Among the four EEP-loaded concentrations, the nanoemulsion with 150 ng showed outstanding features. Using a simulated medium, 150 and 200 ng of EEP-loaded chitosan nanoemulsion concentrations can stop zearalenone production in Fusarium media with complete fungi inhibition. Also, it reduced aflatoxins production in Aspergillus media, with fungal inhibition (up to 47.18%). These results recommended the EEP-chitosan application for pharmaceutics and medical use as a comprehensive wound healing agent. Full article

The milk’s natural flora, or the starter, can preserve cheesemaking and allow for microbial competition. This investigation aimed to improve cheese safety and assess its characteristics using probiotic cell pellets (LCP) or cell-free extracts (CFS). Cheese samples were collected from different areas to investigate the current contamination situation. Six CFSs of probiotics were assessed as antifungal against toxigenic fungi using liquid and solid media and their aflatoxin reduction impact. The most effective CFS was chosen for cheese coating in nanoemulsion. Coated cheese with CFS, LCP, and LCP-CFS was assessed against control for changes in chemical composition, ripening indications, rheological properties, and microbiology. Results showed significant contamination levels in the collected samples, and toxic fungi were present. Lactobacillus rhamnosus CFS has aflatoxins reducibility in liquid media. During cheese ripening, uncoated cheese showed higher fat, protein, salt content, soluble nitrogen, total volatile fatty acids, tyrosine, and tryptophan contents than coated samples, except for LCP-coating treatment. Cheese rheology indicated that coating treatments had the lowest hardness, cohesiveness, gumminess, chewiness, and springiness compared to uncoated cheese. Uncoated cheese had the highest yeast and mold counts compared to the treated ones. The LCP-CFS-coated cheese showed no Aspergillus cells for up to 40 days. Uncoated Ras cheese recorded slightly lower flavor, body, texture, and appearance scores than coated cheeses. In conclusion, coating cheese with L. rhamnosus nanoemulsion has antifungal and antiaflatoxigenic properties, even for LCP, CFS, and CFS-LCP, which could extend cheese shelf life. Full article

Five Aspergillus sections have members that are established agricultural pests and producers of different metabolites, threatening global food safety. Most of these pathogenic Aspergillus species have been isolated from almost all major biomes. The soil remains the primary habitat for most of these cryptic fungi. This review explored some of the ecological attributes that have contributed immensely to the success of the pathogenicity of some members of the genus Aspergillus over time. Hence, the virulence factors of the genus Aspergillus, their ecology and others were reviewed. Furthermore, some biological control techniques were recommended. Pathogenic effects of Aspergillus species are entirely accidental; therefore, the virulence evolution prediction model in such species becomes a challenge, unlike their obligate parasite counterparts. In all, differences in virulence among organisms involved both conserved and species-specific genetic factors. If the impacts of climate change continue, new cryptic Aspergillus species will emerge and mycotoxin contamination risks will increase in all ecosystems, as these species can metabolically adjust to nutritional and biophysical challenges. As most of their gene clusters are silent, fungi continue to be a source of underexplored bioactive compounds. The World Soil Charter recognizes the relevance of soil biodiversity in supporting healthy soil functions. The question of how a balance may be struck between supporting healthy soil biodiversity and the control of toxic fungi species in the field to ensure food security is therefore pertinent. Numerous advanced strategies and biocontrol methods so far remain the most environmentally sustainable solution to the control of toxigenic fungi in the field. Full article

Phenyllactic acid (PLA), a promising food preservative, is safe and effective against a broad spectrum of food-borne pathogens. However, its mechanisms against toxigenic fungi are still poorly understood. In this study, we applied physicochemical, morphological, metabolomics, and transcriptomics analyses to investigate the activity and mechanism of PLA inhibition of a typical food-contaminating mold, Aspergillus flavus. The results showed that PLA effectively inhibited the growth of A. flavus spores and reduced aflatoxin B₁ (AFB₁) production by downregulating key genes associated with AFB₁ biosynthesis. Propidium iodide staining and transmission electron microscopy analysis demonstrated a dose-dependent disruption of the integrity and morphology of the A. flavus spore cell membrane by PLA. Multi-omics analyses showed that subinhibitory concentrations of PLA induced significant changes in A. flavus spores at the transcriptional and metabolic levels, as 980 genes and 30 metabolites were differentially expressed. Moreover, KEGG pathway enrichment analysis indicated PLA-induced cell membrane damage, energy-metabolism disruption, and central-dogma abnormality in A. flavus spores. The results provided new insights into the anti-A. flavus and -AFB₁ mechanisms of PLA. Full article

Alternaria fungi are widely distributed plant pathogens that invade crop products, causing significant economic damage. In addition, toxic secondary metabolites produced by the fungi can also endanger consumers. Many of these secondary metabolites are chemically characterized as mycotoxins. In this study, Q Exactive Orbitrap mass spectrometry was used for the non-targeted analysis of the metabolome of seven Alternaria isolates cultured on Potato Carrot Agar (PCA), Potato Dextrose Agar (PDA) and Potato Sucrose Agar (PSA) medium. Due to the difficulty of detecting modified toxins, an analytical strategy with multiple visual analysis tools was also used to determine the presence of sulfate conjugated toxins, as well as to visualize the molecular network of Alternaria toxins. The results show that PSA medium exhibits more advantageous properties for the culture of Alternaria, with more toxigenic species and quantities and more obvious metabolic pathways. Based on high-resolution tandem mass spectrometry (MS/MS) data, the mycotoxins and their metabolites were mainly clustered into four groups: alternariol (AOH)/alternariol monomethyl ether (AME)/altenusin (ALU)/altenuene (ALT)/dehydroaltenusin (DHA)/Desmethyldehydroaltenusin (DMDA) families, Altertoxin-I (ATX-I) family, tentoxin (TEN) family and tenuazonic acid (TeA) family. Moreover, the PSA medium is more suitable for the accumulation of AOH, AME, ALU, ALT, DHA and DMDA, while the PDA medium is more suitable for the accumulation of ATX-I, TEN and TeA. This research may provide theoretical support for the metabolomics study of Alternaria. Full article

Aspergillus fumigatus is a ubiquitous opportunistic pathogen. We have previously reported that volatile organic compounds (VOCs) produced by A. fumigatus cause delays in metamorphosis, morphological abnormalities, and death in a Drosophila melanogaster eclosion model. Here, we developed A. fumigatus deletion mutants with blocked oxylipin biosynthesis pathways (∆ppoABC) and then exposed the third instar larvae of D. melanogaster to a shared atmosphere with either A. fumigatus wild-type or oxylipin mutant cultures for 15 days. Fly larvae exposed to VOCs from wild-type A. fumigatus strains exhibited delays in metamorphosis and toxicity, while larvae exposed to VOCs from the ∆ppoABC mutant displayed fewer morphogenic delays and higher eclosion rates than the controls. In general, when fungi were pre-grown at 37 °C, the effects of the VOCs they produced were more pronounced than when they were pre-grown at 25 °C. GC–MS analysis revealed that the wild-type A. fumigatus Af293 produced more abundant VOCs at higher concentrations than the oxylipin-deficient strain Af293∆ppoABC did. The major VOCs detected from wild-type Af293 and its triple mutant included isopentyl alcohol, isobutyl alcohol, 2-methylbutanal, acetoin, and 1-octen-3-ol. Unexpectedly, compared to wild-type flies, the eclosion tests yielded far fewer differences in metamorphosis or viability when flies with immune-deficient genotypes were exposed to VOCs from either wild-type or ∆ppoABC oxylipin mutants. In particular, the toxigenic effects of Aspergillus VOCs were not observed in mutant flies deficient in the Toll (spz⁶) pathway. These data indicate that the innate immune system of Drosophila mediates the toxicity of fungal volatiles, especially via the Toll pathway. Full article

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. Full article

The support of trends in agriculture with limited or restricted use of pesticides is linked to the difficulty of protection against pathogenic and toxigenic fungi. Therefore, it is a great challenge to find alternatives to these dangerous fungi. These alternatives include using safe antifungal plant substances of medicinal or aromatic plants as components of botanical pesticides. Within 69 plant species, only 13 were selected as potentially of interest. However, the species Krameria lappacea, whose extraction yield (economic factor) achieved 17.6% and minimum inhibitory concentrations (MIC₅₀) 0.11–1.24 mg mL⁻¹, was found to be enormously advantageous. Extraordinary efficacy on a set of dangerous filamentous fungi, comparable to expensive essential oils or active phenolic compounds, was demonstrated. In the most effective extract fraction, two main substances from the group of neolignans, analogues of kramerixin, were detected by using GC-MS and LC-MS analysis, and their molecular structure was determined. The advantage of K. lappacea was discussed on the basis of the mode of action and chemical properties of the detected neolignans. K. lappacea could be a suitable source for environmentally friendly preparations, thanks to its high yield in simple extraction, excellent antifungal activity, broad antifungal spectrum, harmlessness, and assumed lower volatility of active compounds. Full article

Studies of the biodiversity of plant pathogenic and toxigenic fungi are attracting great attention to improve the predictability of their epidemics and the development of their control programs. Two hundred maize grain samples were gathered from 25 maize-growing governorates in Egypt and 189 samples were processed for the isolation and identification of seed-borne fungal microbiome. Twenty-six fungal genera comprising 42 species were identified according to their morphological characteristics and ITS DNA sequence analysis. Occurrence and biodiversity indicators of these fungal species were calculated. Ustilago maydis, Alternaria alternata, Aspergillus flavus, A. niger, Penicillium spp., Cladosporium spp. and Fusarium verticillioides were the highly frequent (>90% for each), recording the highest relative abundance (˃50%). Al-Menia governorate showed the highest species diversity and richness, followed by Sohag, Al-Nobaria and New Valley governorates. Correlations of 18 fungal species with temperature, relative humidity, precipitation, wind speed, and solar radiation were analyzed using canonical correspondence analysis. Results showed that relative humidity, temperature, and wind speed, respectively, were the most impactful weather variables. However, the occurrence and distribution of these fungi were not clearly grouped into the distinctive climatic regions in which maize crops are grown. Monitoring the occurrence and distribution of the fungal pathogens of maize grains in Egypt will play an important role in predicting their outbreaks and developing appropriate future management strategies. The findings in this study may be useful to other maize-growing countries that have similar climatic conditions. Full article

Gibberella ear rot (GER) is an important fungal ear pathogen of maize that causes ear rot and toxin contamination. Most previous works have only dealt with the visual symptoms, but not with the toxins of GER. As food and feed safety rankings depend on toxin contamination, including deoxynivalenol (DON), without toxins, nothing can be said about the risks involved in food and feed quality. Therefore, three susceptible, three medium-susceptible, and three medium-resistant mother lines were crossed with three testers with differing degrees of resistance and tested between 2017–2020. Two plot replicates and two fungal strains were used separately. The highest heterosis was found at the GER% with a 13% increase across 27 hybrids, including 7 hybrids showing negative heterosis (a higher hybrid performance above the parental mean), with a variance ranging between 63.5 and −55.4. For DON, the mean heterosis was negative at −35%, and only 10 of the 27 hybrids showed a positive heterosis. The mean heterosis for DON contamination, at 1% GER, was again negative (−19.6%, varying between 85% and 224%). Only 17 hybrids showed heterosis, while that of the other 17 was rated higher than the parental mean. A positive significant correlation was found only for GER% and DON; the other factors were not significant. Seven hybrids were identified with positive (2) or negative (5) heterosis for all traits, while the rest varied. For DON and GER, only 13 provided identical (positive or negative) heteroses. The majority of the hybrids appeared to diverge in the regulation of the three traits. The stability of GER and DON (variance across eight data sets) did not agree—only half of the genotypes responded similarly for the two traits. The genetic background for this trait is unknown, and there was no general agreement between traits. Thus, without toxin analyses, the evaluation of food safety is not possible. The variety in degrees of resistance to toxigenic fungi and resistance to toxin accumulation is an inevitable factor. Full article

Microbiodiversity is usually correlated with environmental conditions. This investigation is a case study to cover the lack of knowledge on the correlation of biochemical, physiological, and molecular attributes with the distribution of seed-borne pathogenic fungi of maize under the environmental conditions of the Kingdom of Saudi Arabia to help forecast any destructive epidemics. Forty-one fungal species belonging to 24 genera were detected using standard moist blotter (SMB), deep freezing blotter (DFB), and agar plate (AP) techniques. SMB was superior in detecting the maximum numbers (36 species) of seed-borne mycoflora. The pathogenicity assay revealed that, among 18 seed-borne fungal pathogens used, 12 isolates caused high percentages of rotted seeds and seedling mortality symptoms, which were identified molecularly using an internal transcribed spacer sequence. Two Curvularia spp. and Sarocladium zeae were reported for the first time in KSA. The strains showed various enzymatic activities and amino acid profiles under different environmental setups. Temperature and humidity were the environmental variables influencing the fungal pathogenicity. The highest pathogenicity was correlated with the presence and concentration of threonine, alanine, glutamic, aspartic acids, and protein. The study concluded with the discovery of four new phytopathogens in KSA and, further, evidenced a marked correlation among the investigated variables. Nevertheless, more studies are encouraged to include additional physiological properties of the phytopathogens, such as toxigenic activity, as well as extend the fungal biodiversity study to other plants. Full article