Effective chemical management for prevention of aflatoxins in maize

The presence of aflatoxins in maize grain has been an increasing problem in the Mediterranean area, possibly due to climate change such as increased temperatures and extended drought periods. It is therefore important to prevent the growth of aflatoxigenic Aspergillus species in the field. There are no fungicides registered for control A. flavus in maize, so this study investigated the efficacy of azoxystrobin, boscalid, cyprodinil, fludioxonil and cyprodinil + fludioxonil to reduce A. flavus growth, sporulation and aflatoxin production in in vitro, and in maize field studies. Based on in vitro inhibition of mycelial growth, the most effective fungicides were cyprodinil (EC50 0.5 μg mL-1. Further evaluation of the fungicides on maize seeds infected with A. flavus demonstrated that all the fungicides reduced conidium production by 76 to 94%, and reduced aflatoxin contamination. In a 2-year field study, application of cyprodinil + fludioxonil reduced A. flavus ear rot severity by 40%, and was the most effective formulation for reducing aflatoxin contamination, by 83%. The other four single ingredient fungicides also decreased aflatoxin production on maize kernels (fludioxonil by 80%, cyprodinil by 75%, boscalid by 74% and azoxystrobin by 67%). Field data from this study provide farmers with a new effective chemical approach to control A. flavus and aflatoxin production in maize within an integrated strategy for management of aflatoxins in maize

Effective chemical management for prevention of aflatoxins in maize

The presence of aflatoxins in maize grain has been an increasing problem in the Mediterranean area, possibly due to climate change such as increased temperatures and extended drought periods. It is therefore important to prevent the growth of aflatoxigenic Aspergillus species in the field. There are no fungicides registered for control A. flavus in maize, so this study investigated the efficacy of azoxystrobin, boscalid, cyprodinil, fludioxonil and cyprodinil + fludioxonil to reduce A. flavus growth, sporulation and aflatoxin production in in vitro, and in maize field studies. Based on in vitro inhibition of mycelial growth, the most effective fungicides were cyprodinil (EC50 < 0.05 μg mL-1) and fludioxonil (EC50 <0.11 μg mL-1), while the least effective was boscalid (EC50 4.35-4.50 μg mL-1). Azoxystrobin almost completely inhibited the conidium germination at > 0.5 μg mL-1. Further evaluation of the fungicides on maize seeds infected with A. flavus demonstrated that all the fungicides reduced conidium production by 76 to 94%, and reduced aflatoxin contamination. In a 2-year field study, application of cyprodinil + fludioxonil reduced A. flavus ear rot severity by 40%, and was the most effective formulation for reducing aflatoxin contamination, by 83%. The other four single ingredient fungicides also decreased aflatoxin production on maize kernels (fludioxonil by 80%, cyprodinil by 75%, boscalid by 74% and azoxystrobin by 67%). Field data from this study provide farmers with a new effective chemical approach to control A. flavus and aflatoxin production in maize within an integrated strategy for management of aflatoxins in maize

Analysis of volatile emissions from grape berries infected with Aspergillus carbonarius using hyphenated and portable mass spectrometry

Mycotoxins represent a serious risk for human and animal health. Οchratoxin A (OTA) is a carcinogenic mycotoxin produced by A. carbonarius that constitutes a severe problem for viticulture. In this study, we investigate the development of novel detection and on-line monitoring approaches for the detection of OTA in the field (i.e. out of the chemical laboratory) using advanced molecular sensing. Both stand-alone and hyphenated mass spectrometry (MS) based systems (e.g. Time-of-Flight ToF–MS and gas chromatography GC combined with MS) and compact portable membrane inlet MS (MIMS) have been employed for the first time to detect and monitor volatile emissions of grape berries infected by the fungus Aspergillus carbonarius. In vacuo (electron impact—EI) and ambient ionisation (electrospray ionisation—ESI) techniques were also examined. On-line measurements of the volatile emissions of grape berries, infected by various strains of A. carbonarius with different toxicity levels, were performed resulting in different olfactory chemical profiles with a common core of characteristic mass fragments, which could be eventually used for on-site detection and monitoring allowing consequent improvement in food security.ISSN:2045-232

From Grapes to Wine: Impact of the Vinification Process on Ochratoxin A Contamination

Ochratoxin A (OTA) is one of the major mycotoxins, classified as “potentially carcinogenic to humans” (Group 2B) by the International Agency for Research on Cancer (IARC), and wine is one of its main sources of intake in human consumption. The main producer of this toxin is Aspergillus carbonarius, a fungus that contaminates grapes early in the growing season. The vinification process, as a whole, reduces the toxin content in wine compared to the grapes; however, not all vinification steps contribute equally to this reduction. During the maceration phase in red wines, toxin concentrations generally tend to increase. Based on previous studies, this review provides an overview of how each step of the vinification process influences the final OTA contamination in wine. Moreover, certain physical, chemical, and microbiological post-harvest strategies are useful in reducing OTA levels in wine. Among these, the use of fining agents, such as gelatin, egg albumin, and bentonite, must be considered. Therefore, this review describes the fate of OTA during the winemaking process, including quantitative data when available, and highlights actions able to reduce the final OTA level in wine

Biological control strategies of mycotoxigenic fungi and associated mycotoxins in Mediterranean basin crops

Fungi that belong to the genera Aspergillus, Fusarium, and Penicillium pose serious phytopathological and mycotoxicological risks at pre-harvest and post-harvest stages, as well as in processed food products because they can produce several mycotoxins. Mycotoxins pose a serious problem for animal and human health and have a significant economic impact worldwide. The Mediterranean basin is a large geographical region with a temperate climate supporting the cultivation of a wealth of field and greenhouse crops with a high risk of mycotoxin contamination. The most important mycotoxins that occur in the Mediterranean basin are aflatoxins (B1, B2, G1 and G2) in dried fruits and nuts, ochratoxin A in grapes and raisins as well as trichothecenes and fumonisins in cereals. A variety of chemical, biological and physical strategies have been developed to control the mycotoxigenic pathogens; to minimize mycotoxin production at pre- or post-harvest level; to contribute to decontamination and/or detoxification of mycotoxins from contaminated foods and feeds; or to inhibit mycotoxin absorption in the gastrointestinal tract. Biological control using microbial antagonists either alone or as part of an integrated control strategy to reduce pesticide inputs, has emerged as a promising approach for control of mycotoxins in crops, both pre- and post-harvest. Several organisms including atoxigenic Aspergilli, yeasts, bacteria and fungi have been tested for their ability to reduce both fungal infection and mycotoxin contamination. For instance, atoxigenic fungal strains are being used widely to prevent pre-harvest aflatoxin contamination of crops such as peanuts, pistachios, maize, and cottonseed in several parts of the world including the Mediterranean area. Recent advancements in the use of biocontrol strategies have led to registration of commercial products with increased practical applications for the benefit of growers in several countries

Endogenous Lipogenic Regulators of Spore Balance in Aspergillus nidulans

The ability of fungi to produce both meiospores and mitospores has provided adaptive advantages in survival and dispersal of these organisms. Here we provide evidence of an endogenous mechanism that balances meiospore and mitospore production in the model filamentous fungus Aspergillus nidulans. We have discovered a putative dioxygenase, PpoC, that functions in association with a previously characterized dioxygenase, PpoA, to integrate fatty acid derived oxylipin and spore production. In contrast to PpoA, deletion of ppoC significantly increased meiospore production and decreased mitospore development. Examination of the PpoA and PpoC mutants indicate that this ratio control is associated with two apparent feedback loops. The first loop shows ppoC and ppoA expression is dependent upon, and regulates the expression of, nsdD and brlA, genes encoding transcription factors required for meiospore or mitospore production, respectively. The second loop suggests Ppo oxylipin products antagonistically signal the generation of Ppo substrates. These data support a case for a fungal “oxylipin signature-profile” indicative of relative sexual and asexual spore differentiation

AFLA-PISTACHIO: Development of a Mechanistic Model to Predict the Aflatoxin Contamination of Pistachio Nuts

In recent years, very many incidences of contamination with aflatoxin B1 (AFB1) in pistachio nuts have been reported as a major global problem for the crop. In Europe, legislation is in force and 12 μg/kg of AFB1 is the maximum limit set for pistachios to be subjected to physical treatment before human consumption. The goal of the current study was to develop a mechanistic, weather-driven model to predict Aspergillus flavus growth and the AFB1 contamination of pistachios on a daily basis from nut setting until harvest. The planned steps were to: (i) build a phenology model to predict the pistachio growth stages, (ii) develop a prototype model named AFLA-pistachio (model transfer from AFLA-maize), (iii) collect the meteorological and AFB1 contamination data from pistachio orchards, (iv) run the model and elaborate a probability function to estimate the likelihood of overcoming the legal limit, and (v) manage a preliminary validation. The internal validation of AFLA-pistachio indicated that 75% of the predictions were correct. In the external validation with an independent three-year dataset, 95.6% of the samples were correctly predicted. According to the results, AFLA-pistachio seems to be a reliable tool to follow the dynamic of AFB1 contamination risk throughout the pistachio growing season

The U-Box Protein CMPG1 Is Required for Efficient Activation of Defense Mechanisms Triggered by Multiple Resistance Genes in Tobacco and Tomato

We previously identified three Avr9/Cf-9 Rapidly Elicited (ACRE) genes essential for Cf-9– and Cf-4–dependent hypersensitive response (HR) production in Nicotiana benthamiana. Two of them encode putative E3 ubiquitin ligase components. This led us to investigate other ACRE genes associated with the ubiquitination pathway. ACRE74 encodes a U-box E3 ligase homolog, highly related to parsley (Petroselinum crispum) CMPG1 and Arabidopsis thaliana PLANT U-BOX20 (PUB20) and PUB21 proteins, and was called Nt CMPG1. Transcript levels of Nt CMPG1 and the homologous tomato (Solanum lycopersicum) Cmpg1 are induced in Cf9 tobacco (Nicotiana tabacum) and Cf9 tomato after Avr9 elicitation. Tobacco CMPG1 possesses in vitro E3 ligase activity. N. benthamiana plants silenced for Nt CMPG1 show reduced HR after Cf-9/Avr9 elicitation, while overexpression of Nt CMPG1 induces a stronger HR in Cf9 tobacco plants after Avr9 infiltration. In tomato, silencing of Cmpg1 decreased resistance to Cladosporium fulvum. Overexpression of epitope-tagged tobacco CMPG1 mutated in the U-box domain confers a dominant-negative phenotype. We also show that Nt CMPG1 is involved in the Pto/AvrPto and Inf1 responses. In summary, we show that the E3 ligase Nt CMPG1 is essential for plant defense and disease resistance