An Overview of Aspergillus Species Associated with Plant Diseases

The genus Aspergillus contains several species that are important plant pathogens. Plant pathogenic Aspergillus spp. affect agricultural crops in the field as well as after harvest, often associated with corn ear rot, cotton boll rot, peanut yellow mold, black mold of onion and garlic, fruit rot on grapes, pomegranates, olives, citrus, and apples. Coffee berries and coffee beans as well as tree nuts are also frequently infected by Aspergillus spp. Some of the plant pathogenic Aspergillus spp. are also mycotoxigenic, produced mycotoxin in the plant tissues leading to contamination of agricultural products. Over the years, reports of plant diseases caused by Aspergillus in various crops have increased, suggesting they are commonly encountered plant pathogens. This review focuses on agricultural crops or cultivated plants infected by Aspergillus spp. The compilation of plant pathogenic Aspergillus spp. provides information to mycologists, particularly those involved in plant pathology and crop protection, with updated information on plant diseases caused by various species of Aspergillus. The updated information also includes the locality or location, province, state and the country. The knowledge on the prevalence and geographic distribution of plant pathogenic Aspergillus spp. is beneficial in the application of crop protection.

Description and management of Aspergillus section Nigri causing post-harvest bulbs rot of onion

When onions are improperly stored, a post-harvest disease known as black mold of onion bulbs can result in considerable economic losses. Aspergillus section Nigri, one of many species, has been implicated in the development of black mold. In the present study, rot onion bulbs were collected from markets in Qena, Egypt. Thirteen Aspergillus section Nigri isolates were obtained and identified by morphological and molecular characterization. The ochratoxins potential of isolated A. section Nigri was tested, and three isolates were producers at the range of 1.5-15 ppm. For the presence of pks gene, no amplification product was detected. Using the fungal growth inhibition test, the isolates of A. niger were inhibited by eco-friendly materials Cement and Zeolite. Cement exhibited maximum percentage growth inhibition against the tested isolates at 74.7-86.7%. The pathogenicity activity of the A. niger isolates was tested by inoculation of healthy onion bulbs, other onion bulbs covered with Cement and Zeolite before inoculation by A. niger was used. The two treatments significantly reduced bulbs rot disease of onion than untreated bulbs. Seven and nine isolates showed 0% rot on covered bulbs by Cement and Zeolite, respectively as compared with inoculated onions, which exhibited rot ranging from 55 to 80%. Using eco-friendly materials with efficiency against post-harvest bulbs rot of onion was evaluated in this study.

Black aspergilli in Brazilian onions: From field to market

The occurrence of black aspergilli in onions has been reported as frequent, and this group of fungi harbors potentially toxigenic species. In addition, Aspergillus niger has been reported as the causative agent of black mold rot, an important postharvest disease that causes damage throughout the world. Brazil stands out as one of the world's largest onion producers. However, few studies have been conducted to investigate the mycobiota in Brazilian onions. For this reason, we investigated the mycobiota of 48 market (n = 25) and field (n = 23) onion bulb samples. Nineteen soil samples were collected from the same fields and evaluated. In field onions and soil samples, Penicillium spp. was the prevalent fungal group, whereas in market samples A. section Nigri was the most frequent group. Due to the taxonomic complexity of this group, species identification was supported by phylogenetic data (CaM gene). A. welwitschiae was the most prevalent species in market samples. Black aspergillus strains were evaluated for fumonisin B₂ (FB₂) and ochratoxin A (OTA) production. Overall, 53% and 2.2% of the strains produced FB₂ and OTA, respectively. The occurrence of FB₂ and OTA was also investigated in onion bulb samples but none showed contamination with these mycotoxins.

Molecular analysis of Aspergillus section Nigri isolated from onion samples reveals the prevalence of A. welwitschiae

The aim of this study was to isolate Aspergillus section Nigri from onion samples bought in supermarkets and to analyze the fungal isolates by means of molecular data in order to differentiate A. niger and A. welwitschiae species from the other non-toxigenic species of black aspergilli, and detect genes involved in the biosynthesis of ochratoxin A and fumonisin B₂. Aspergillus section Nigri were found in 98% (94/96) of the onion samples. Based on the results of multiplex PCR (performed on 500 randomly selected strains), 97.4% of the Aspergillus section Nigri strains were recognized as A. niger/A. welwitschiae. Around half of them were subjected to partial sequencing of the CaM gene to distinguish one from the other. A total of 97.9% of the isolates were identified as A. welwitschiae and only 2.1% as A. niger. The fum8 gene, involved in fumonisin B₂ biosynthesis, was found in 36% of A. welwitschiae isolates, but radH and pks genes, involved in ochratoxin A biosynthesis, were found in only 2.8%. The presence/absence of fum8 gene in the A. welwitschiae genome is closely associated with ability/inability of the isolates to produce fumonisin in vitro. Based on these results, we suggest that in-depth studies are conducted to investigate the presence of fumonisins in onion bulbs.

Toxicological and Medical Aspects of Aspergillus-Derived Mycotoxins Entering the Feed and Food Chain

Due to Earth's changing climate, the ongoing and foreseeable spreading of mycotoxigenic Aspergillus species has increased the possibility of mycotoxin contamination in the feed and food production chain. These harmful mycotoxins have aroused serious health and economic problems since their first appearance. The most potent Aspergillus-derived mycotoxins include aflatoxins, ochratoxins, gliotoxin, fumonisins, sterigmatocystin, and patulin. Some of them can be found in dairy products, mainly in milk and cheese, as well as in fresh and especially in dried fruits and vegetables, in nut products, typically in groundnuts, in oil seeds, in coffee beans, in different grain products, like rice, wheat, barley, rye, and frequently in maize and, furthermore, even in the liver of livestock fed by mycotoxin-contaminated forage. Though the mycotoxins present in the feed and food chain are well documented, the human physiological effects of mycotoxin exposure are not yet fully understood. It is known that mycotoxins have nephrotoxic, genotoxic, teratogenic, carcinogenic, and cytotoxic properties and, as a consequence, these toxins may cause liver carcinomas, renal dysfunctions, and also immunosuppressed states. The deleterious physiological effects of mycotoxins on humans are still a first-priority question. In food production and also in the case of acute and chronic poisoning, there are possibilities to set suitable food safety measures into operation to minimize the effects of mycotoxin contaminations. On the other hand, preventive actions are always better, due to the multivariate nature of mycotoxin exposures. In this review, the occurrence and toxicological features of major Aspergillus-derived mycotoxins are summarized and, furthermore, the possibilities of treatments in the medical practice to heal the deleterious consequences of acute and/or chronic exposures are presented.

A study of the 2013 Western European issue of aflatoxin contamination of maize from the Balkan area

In March 2013 a large shipment of maize, intended for feed was subject of an alert in the Rapid Alert System for Food and Feed of the European Commission (EC) because the aflatoxin B1 (AFB1) level in the load exceeded the EC regulated maximum level of 20 μg/kg. Since the shipment had passed import controls and was already distributed (mainly to German farms), a massive recall followed. The aim of the current study was to investigate questions, raised by authorities and industry, related to the effectivity of EU sampling procedures, the influence of sample homogenisation procedures and sample storage conditions on the test results, and fungal identification as unexpected mycotoxins were identified during this study. The Netherlands Food and Consumer Product Safety Authority seized a shipload of maize in July 2013, suspected to be contaminated with AFB1. The shipload was sampled according to the 2009 and 2013 EC Sampling Regulations to compare the outcomes of both sampling protocols. Mycotoxin analysis of the incremental samples showed high mean levels of AFB1, aflatoxin G1 (AFG1), and ochratoxin A (OTA). Also an extreme inhomogeneous distribution of aflatoxins and OTA was proven. Analysis of samples homogenised according to the slurry method showed improved performance as compared to samples homogenised through dry homogenisation. Sampling and sample homogenisation according to the Regulation from 2013 showed a closer estimate of the ‘true’ AFB1 content as compared to sampling according to the Regulation from 2009. No influence of laboratory storage conditions on AFB1 concentration could be determined. Fungal identification revealed Aspergillus flavus as the main source of AFB1 in this shipment. Infrequent occurrence of Aspergillus parasiticus might have been the source of AFG1. The occurrence of sometimes large amounts of OTA could not be explained, however it was suggested that Aspergillus welwitschiae might have played a role.

Developments in mycotoxin analysis: an update for 2012-2013

This review highlights developments in mycotoxin analysis and sampling over a period between mid-2012 and mid-2013. It covers the major mycotoxins: aflatoxins, Alternaria toxins, ergot alkaloids, fumonisins, ochratoxins, patulin, trichothecenes and zearalenone. A wide range of analytical methods for mycotoxin determination in food and feed were developed last year, in particular immunochemical methods and liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS)-based methods. After a section on sampling and sample preparation, due to the rapid spread and developments in the field of LC-MS/MS multimycotoxin methods, a separate section has been devoted to this area of research. It is followed by a section on mycotoxins in botanicals and spices, before continuing with the format of previous reviews in this series with dedicated sections on method developments for the individual mycotoxins.

Aspergillus luchuensis, an industrially important black Aspergillus in East Asia

Aspergilli known as black- and white-koji molds which are used for awamori, shochu, makgeolli and other food and beverage fermentations, are reported in the literature as A. luchuensis, A. awamori, A. kawachii, or A. acidus. In order to elucidate the taxonomic position of these species, available ex-type cultures were compared based on morphology and molecular characters. A. luchuensis, A. kawachii and A. acidus showed the same banding patterns in RAPD, and the three species had the same rDNA-ITS, β-tubulin and calmodulin sequences and these differed from those of the closely related A. niger and A. tubingensis. Morphologically, the three species are not significantly different from each other or from A. niger and A. tubingensis. It is concluded that A. luchuensis, A. kawachii and A. acidus are the same species, and A. luchuensis is selected as the correct name based on priority. Strains of A. awamori which are stored in National Research Institute of Brewing in Japan, represent A. niger (n = 14) and A. luchuensis (n = 6). The neotype of A. awamori (CBS 557.65 =  NRRL 4948) does not originate from awamori fermentation and it is shown to be identical with the unknown taxon Aspergillus welwitschiae. Extrolite analysis of strains of A. luchuensis showed that they do not produce mycotoxins and therefore can be considered safe for food and beverage fermentations. A. luchuensis is also frequently isolated from meju and nuruk in Korea and Puerh tea in China and the species is probably common in the fermentation environment of East Asia. A re-description of A. luchuensis is provided because the incomplete data in the original literature.

Role of Aspergilli and Penicillia in mycotoxin contamination of maize in Hungary

Aspergillus and Penicillium species and their mycotoxins, including aflatoxins, ochratoxins, fumonisins and patulin, are frequently encountered on cereal products. The occurrence of these species and their mycotoxins on maize was investigated in Hungary after harvest in two consecutive years. Surface-sterilized cereal seeds were placed on selective media, and the isolated fungal strains were identified using morphological methods. In 2010 and 2011, 81.94% and 14.33%, respectively, of the samples were found to be contaminated with potentially toxigenic isolates. The species identification of selected isolates was carried out using sequence-based methods. Several Aspergillus flavus isolates were identified, which are potential aflatoxin producers. Other mycotoxinproducing species were also isolated, including black Aspergilli, which potentially produce ochratoxins and fumonisins, and A. clavatus, which produces patulin. In 2010 a large number of Penicillium species occurred in the samples, producing a wide range of mycotoxins. The mycotoxin content of the samples was analysed using the ELISA and HPLC techniques. Aflatoxins were not detected in any of the samples, while ochratoxins and fumonisins were successfully identified in some of the maize seeds.