Environmental factors modify carbon nutritional patterns and niche overlap between Aspergillus flavus and Fusarium verticillioides strains from maize.

This study examined the utilization patterns of key carbon sources (CS, 24: including key sugars, amino acids and fatty acids) in maize by strains of Aspergillus flavus and Fusarium verticillioides under different water activity (aw, 0.87–0.98 aw) and temperature (20–35 °C) values and compared the niche overlap indices (NOI) that estimate the in vitro CS utilization profiles [Wilson, M., Lindow, S.E., 1994. Coexistence among epiphytic bacterial populations mediated through nutritional resource partitioning. Applied and Environmental Microbiology 60, 4468–4477.]. The ability to grow in these key CS in minimal media was studied for 120 h in 12 h steps. The NOI was calculated for inter-species (F. verticillioides–A. flavus) and for intra-species (A. flavus–A. flavus) using CS utilization patterns over the range of interacting environmental conditions. 30 °C, over the whole aw range examined, was found to be optimal for utilization of the maximum number of CS by A. flavus. In contrast, for F. verticillioides this was more so at 20 °C; 25 °C allowed a suboptimal usage of CS for both species. NOIs confirmed the nutritional dominance of A. flavus at 30 °C, especially at lower aw levels and that of F. verticillioides at 20 °C, mainly at 0.95 aw. In other conditions of aw, based on CS utilization patterns, the data indicated that A. flavus and F. verticillioides occupied different ecological niches. The variability in nutritional sources utilization between A. flavus strains was not related to their ability to produce aflatoxins (AFs). This type of data helps to explain the nutritional dominance of fungal species and strains under different environmental conditions. This could be useful in trying to find appropriate natural biocontrol microorganisms to compete with these mycotoxigenic species

Open field study of some Zea mays hybrids, lipid compounds and fumonisins accumulation

Lipid molecules are increasingly recognized as signals exchanged by organisms interacting in pathogenic and/or symbiotic ways. Some classes of lipids actively determine the fate of the interactions. Host cuticle/cell wall/membrane components such as sphingolipids and oxylipins may contribute to determining the fate of host–pathogen interactions. In the present field study, we considered the relationship between specific sphingolipids and oxylipins of different hybrids of Zea mays and fumonisin by F. verticillioides, sampling ears at different growth stages from early dough to fully ripe. The amount of total and free fumonisin differed significantly between hybrids and increased significantly with maize ripening. Oxylipins and phytoceramides changed significantly within the hybrids and decreased with kernel maturation, starting from physiological maturity. Although the correlation between fumonisin accumulation and plant lipid profile is certain, the data collected so far cannot define a cause-effect relationship but open up new perspectives. Therefore, the question—“Does fumonisin alter plant lipidome or does plant lipidome modulate fumonisin accumulation?”—is still open

Impact of environmental and plant factors on Aspergillus section Flavi isolated from maize in Italy

The exceptional hot weather conditions in Italy during the summer of 2003 resulted in an optimal environment for the development of Aspergillus section Flavi in maize and, consequently, for aflatoxin production. This caused significant contamination, above the EU legal limits, for maize destined to feed and food. This study was focused to define the distribution of these fungi in Italy for the first time. In all the sampled regions of Northern Italy, A. flavus was present. Ecological studies were conducted and this defined the cardinal conditions of water availability (0.83-0.99 aw), temperature (15-45°C) and gas composition (CO2<50%) for sporulation, growth and aflatoxin B1 production. Since in the field A. flavus does not occur alone, possible interactions with the fumonisin producing species Fusarium verticillioides was examined by using carbon source utilisation patterns and niche overlap indices. F. verticillioides was a better competitor over the range 0.93-0.98 aw and temperature of 20°C while A. flavus dominated at 0.98 aw and 30°C. Inoculum concentration (10 1 -10 7 CFUs ml) affected infection efficiency, with a low percentage of kernels becoming infected with up to 10 5 conidia mL -1 , and early maize growth stages were more susceptible. A total of 34 maize hybrids were screened for resistance to A. flavus and aflatoxin production and this showed that about 40% of these showed promise. The data sets obtained in this study wil provide a powerful basis for the development of a Decision Support System to minimize aflatoxins in maize.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Occurrence of ochratoxin A-producing fungi in grapes grown in Italy

A study was carried out to investigate fungi present on grapes grown in Italy. Aspergillus and Penicillium spp. isolates were identified and studied in vitro, and their ability to produce ochratoxin A (OA) was investigated. The survey involved nine vineyards, three located in northern Italy and six located in southern Italy. In 1999 and 2000, bunches of grapes at different growth stages were collected from all nine vineyards, and berry samples were placed in moist chambers and incubated. The resultant fungal colonies were then transferred to petri dishes containing Czapek yeast agar and incubated at 25 degrees C for 7 days; the fungal isolates were identified and then cultivated in liquid Czapek yeast medium and evaluated for their ability to produce OA. During the survey, 508 isolates were collected, with 477 belonging to Aspergillus spp. and 31 belonging to Penicillium spp. Among the aspergilli, species of the Fumigati, Circumdati, and Nigri sections were identified, with species of the Nigri section (464 isolates) largely predominating; for species of the Nigri section, 108 isolates were uniseriate, 270 were biseriate, and 86 were identified as Aspergillus carbonarius. Black aspergilli isolated over the 2 years of the study showed a very similar pattern. On average, the biseriates represented about 60% of the isolates collected in both years and were followed by uniseriates (21%) and A. carbonarius (19%). The most toxigenic strains proved to be those of A. carbonarius; about 60% of these isolates were OA producers and produced the highest levels of OA. A. carbonarius was more frequent in the south, but in both areas the percentages of OA-producing isolates remained the same

Penicillium populations in dry-cured ham manufacturing plants.

Seven ham manufacturing plants were sampled for 1 year to assess the mycoflora present in the air and on hams, with special attention given to potential mycotoxin producers. Temperature and relative humidity were recorded in the ripening rooms. Maturing rooms held hams from 2 to 3 through 6 to 7 ripening months, and aging rooms held hams for the following 6 to 7 months, until the 14-month ripening point, when they were ready for the market. Mean temperatures and relative humidities registered during the study were 14.9 degrees C and 62.4%, respectively, in maturing rooms and 16.3 degrees C and 57.6% in aging rooms. Aspergilli and penicillia, potential mycotoxin producers, were isolated in all the plants from the air and the ham. Aspergilli represented 5% of the isolates, while penicillia were largely dominant, with Penicillium nalgiovense being the most represented species (around 60% of the penicillia), followed by Penicillium nordicum, with 10 and 26% of the penicillia isolated, respectively, from the air or the ham. Ochratoxin A production ability, checked in vitro at 250C, was observed in 50% of the P. nordicum isolates obtained both from the air and the ham. Air and ham surface contamination by penicillia was greater in the ripening rooms, where higher temperatures were registered. A certain correlation was also observed between air and ham surface contamination. On the basis of this study, P. nordicum, the ochratoxin A producer that is notable on proteinaceous substrates, is normally present in ham manufacturing plants in Italy, even though not a dominant species. Further studies are necessary to clarify and ensure if dry-curing conditions minimize the potential risk of ochratoxin A formation in the product

Influence of water activity and anti-fungal compounds on development and competitiveness of Fusarium verticillioides

This investigated the roles of water activity (aw) and fungicides on the competitiveness of two Fusarium verticillioides strains against other spoilage fungi commonly present in maize (F. proliferatum, Aspergillus niger, A. flavus, A. ochraceus and Penicillium verrucosum). Fungal strains were inoculated on artificial media containing maize flour. The effects were determined of three aw levels (0.99, 0.98 and 0.95) and three fungicides (tebuconazole, procloraz and prothioconazole) on fungal interactions, the Index of Dominance (ID) of isolates and fumonisin B1+B2 (FBs) production. The two strains of F. verticillioides showed similar behaviour in conditions where water was freely available (0.99 aw); at 0.98 and 0.95 aw both F. verticilliodes strains had the lowest total ID scores (8–6 and 10–12, respectively). They showed the same ability to compete against other fungi having the highest ID scores against P. verrucosum and A. ochraceus and the lowest against A. niger and A. flavus. The lowest water activity gave (0.95 aw) was the most conducive for fumonisin production with significant differences to 0.98 and 0.99 aw. In a co-inoculation experiment, only FBs production from P. verrucosum was greater in the presence of the F. verticilliodes strains other fungi. The use of fungicides reduced Indices of Dominancy (ID) for both F. verticilliodes strains. A significant reduction in F. verticilloides growth was observed when combining water stress and fungicide treatments. This information provides increased understanding of the colonisation patterns of F. verticillioides in relation to other mycobiota and to both environmental and chemical stresses, and has implications in relation to future climate change scenarios

Comparison of different physical methods and preservatives for control of Fusarium proliferatum rot in garlic

Dry rot is an emerging issue for garlic production worldwide and Fusarium proliferatum is its major causal agent. Since the disease is seed-transmitted, sowing healthy cloves is crucial. In this study, some disinfection strategies were tested on garlic seeds, including steam, dry heat, chemical disinfectants and gaseous ozone (O3). Steam reduced the Colony Forming Units·g−1 (CFUs·g−1) by up to 92% in garlic seeds, but, at the same time, it affected their germination (−36%). Similarly, hydrogen peroxide (H2O2) and peracetic acid (C2H4O3) reduced the CFUs·g−1 by up to 83%; however, these methods also severely impaired germination (−40%). Dry heat did not negatively impact germination, but fungal contamination was not significantly reduced. The most promising strategy was gaseous O3 treatment; it decreased CFUs·g−1 by up to 96%, without causing any reduction of germination. The treatments applied were partially effective because the fungus is predominantly located in the outer layer of the seed, although it is also found in the inner portions. Some of these treatments can contribute to garlic protection from seed-borne pathogens and possibly reduce the occurrence of garlic dry rot

Enhancement of agri-food by-products: green extractions of bioactive molecules with fungicidal action against mycotoxigenic fungi and their mycotoxins

IntroductionToday, alternative strategies based on the use of bioactive compounds have been proposed to reduce mycotoxin contamination and limit the use of chemical fungicides. MethodsIn the present work, several by-products collected from the agri-food chain (i.e., red and white grape marc, red grapevine leaves, grape seeds and stalks, pear, apple, green beans, tomato, and spent hops) were subjected to green extraction protocols (i.e., steam distillation, Ultrasound-Assisted, and Naviglio (R) extraction) to obtain extracts rich in polyphenols and terpenes. Each extract was assessed in vitro for its ability to inhibit the development of the main mycotoxigenic species and related mycotoxins. Results and DiscussionAspergillus flavus and A. carbonarius were significantly reduced by pear (from -45 to -47%) and grape marc (from -21 to -51%) extracts, while F. graminearum was shown to be highly influenced by grape stalk, pear, and grape marc extracts (-24% on average). On the contrary, F. verticillioides was inhibited only by pear (-18%) and to a very low and negligible extent by apple (-1%) and green beans (-3%). Regarding the reduction of mycotoxins, the extracts were able to inhibit OTA from 2 to 57%, AFB1 from 5 to 75%, and DON from 14 to 72%. The highest percentages of reduction were obtained against FBs (from 11 to 94%), ZEN (from 17 to 100%), and Alternaria toxins (from 7 to 96%). In conclusion, this work provided promising results for the production of bioactive extracts obtained from agri-food by-products, which could be exploited as potential biofungicides against the development of mycotoxigenic fungi and related mycotoxins

Mycotoxin mixtures in food and feed: holistic, innovative, flexible risk assessment modelling approach: MYCHIF

Mycotoxins are toxic compounds mainly produced by fungi of the genera Aspergillus, Penicillium and Fusarium. They are present, often as mixtures, in many feed and food commodities including cereals, fruits and vegetables. Their ubiquitous presence represents a major challenge to the health and well being of humans and animals. Hundreds of compounds are listed as possible mycotoxins occurring in raw and processed materials destined for human food and animal feed. In this study, mycotoxins of major toxicological relevance to humans and target animal species were investigated in a range of crops of interest (and their derived products). Extensive Literature Searches (ELSs) were undertaken for data collection on: (i) ecology and interaction with host plants of mycotoxin producing fungi, mycotoxin production, recent developments in mitigation actions of mycotoxins in crop chains (maize, small grains, rice, sorghum, grapes, spices and nuts), (ii) analytical methods for native, modified and co-occurring mycotoxins (iii) toxicity, toxicokinetics, toxicodynamics and biomarkers relevant to humans and animals (poultry, suidae (pig, wild boar), bovidae (sheep, goat, cow, buffalo), rodents (rats, mice) and others (horses, dogs), (iv) modelling approaches and key reference values for exposure, hazard and risk modelling. Comprehensive databases were created using EFSA templates and were stored in the MYCHIF platform. A range of approaches were implemented to explore the modelling of external and internal exposure as well as dose-response of mycotoxins in chicken and pigs. In vitro toxicokinetic and in vivo toxicity databases were exploited, both for single compounds and mixtures. However, large data gaps were identified particularly with regards to absence of common statistical and study designs within the literature and constitute an obstacle for the harmonisation of internal exposure and dose-response modelling. Finally, risk characterisation was also performed for humans as well as for two animal species (i.e. pigs and chicken) using available tools for the modelling of internal dose and a component-based approach for selected mycotoxins mixtures