Contamination of cereal commodities by moulds and mycotoxins results in dry matter, quality, and nutritional losses and represents a significant hazard to the food chain. Most grain is harvested, dried and then stored on farm or in silos for medium/long term storage. Cereal quality is influenced by a range of interacting abiotic and biotic factors. In the so-called stored grain ecosystem, factors include grain and contaminant mould respiration, insect pests, rodents and the key environmental factors of temperature, water availability and intergranular gas composition, and preservatives which are added to conserve moist grain for animal feed. Thus knowledge of the key critical control points during harvesting, drying and storage stages in the cereal production chain are essential in developing effective prevention strategies post-harvest. Studies show that very small amounts of dry matter loss due to mould activity can be tolerated. With <0.5% dry matter loss visible moulding, mycotoxin contamination and downgrading of lots can occur. The key mycotoxigenic moulds in partially dried grain are Penicillium verrucosum (ochratoxin) in damp cool climates of Northern Europe, and Aspergillus flavus (aflatoxins), A. ochraceus (ochratoxin) and some Fusarium species (fumonisins, trichothecenes) on temperate and tropical cereals. Studies on the ecology of these species has resulted in modelling of germination, growth and mycotoxin minima and prediction of fungal contamination levels which may lead to mycotoxin contamination above the tolerable legislative limits (e.g. for ochratoxin). The effect of modified atmospheres and fumigation with sulphur dioxide and ammonia have been attempted to try and control mould spoilage in storage. Elevated CO2 of >75% are required to ensure that growth of mycotoxigenic moulds does not occur in partially dried grain. Sometimes, preservatives based on aliphatic acids have been used to prevent spoilage and mycotoxin contamination of stored commodities, especially feed. These are predominantly fungistats and attempts have been made to use alternatives such as essential oils and anti-oxidants to prevent growth and mycotoxin accumulation in partially dried grain. Interactions between spoilage and mycotoxigenic fungi and insect pests inevitably occurs in stored grain ecosystems and this can further influence contamination with mycotoxins. Effective post-harvest management of stored commodities requires clear monitoring criteria and effective implementation in relation to abiotic and biotic factors, hygiene and monitoring to ensure that mycotoxin contamination is minimised and that stored grain can proceed through the food chain for processing.

This paper examines the available information on the potential for climate-change impacts on mycotoxigenic fungi and mycotoxin contamination of food crops pre-and postharvest. It considers the effect of changes in temperature ⁄ water availability on mycotoxin contamination, especially incidences where aflatoxin B 1 and ochratoxin A production has been influenced. The potential of using preharvest models to predict risk from deoxynivalenol (DON) in wheat, fumonisin B 1 in maize and aflatoxins in maize and peanuts in different continents are considered in the context of potential for adaptation to include climate-change scenarios. Available information suggests that slightly elevated CO 2 concentrations and interactions with temperature and water availability may stimulate growth of some mycotoxigenic species, especially under water stress. The accumulated knowledge on interacting conditions of water ⁄ temperature effects on optimum and boundary conditions for growth and mycotoxin production has been used to predict the effects that +3 and +5°C increases under water stress would have on growth ⁄ mycotoxin production by mycotoxigenic species. Various spatial scales, from toxin gene expression to regional approaches using geostatistics, are examined for their use in understanding the impact that climate change may have on food contamination in developing and developed countries. The potential for using an integrated systems approach to link gene expression data, phenotypic toxin production under different interacting abiotic conditions is discussed using Fusarium species and DON as examples. Such approaches may be beneficial for more accurate predictions of risk from mycotoxins on a regional basis and also the potential for new emerging toxin threats.

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Aims: This study investigated the in vitro effects of water activity (a w ; 0AE85-0AE987) and temperature (10-40°C) on growth and ochratoxin A (OTA) production by two strains of Aspergillus carbonarius isolated from wine grapes from three different European countries and Israel on a synthetic grape juice medium representative of mid-veraison (total of eight strains). Methods and Results: The synthetic grape juice medium was modified with glycerol or glucose and experiments carried out for up to 56 days for growth and 25 days for OTA production. The lag phase prior to growth, growth rates and ochratoxin production were quantified. Statistical comparisons were made of all factors and multiple regression analysis used to obtain surface response curves of a w · temperature for the eight strains and optimum growth and OTA production by A. carbonarius. The lag phase increased from <1 day at 25-35°C and 0AE98 a w to >20 days at marginal temperatures and water availabilities. Generally, most A. carbonarius strains grew optimally at 30-35°C, regardless of solute used to modify a w , with no growth at <15°C. The optimum a w for growth varied from 0AE93 to 0AE987 depending on the strain, with the widest a w tolerance at 25-30°C. There was no direct relationship among growth, environmental factors and country of origin of individual strains. Optimum conditions for OTA production varied with strain. Some strains produced optimal OTA at 15-20°C and 0AE95-98 a w . The maximum OTA produced after 10 days was about 0AE6-0AE7 lg g)1 , with a mean production over all eight strains of 0AE2 lg g)1at optimum environmental conditions. Conclusions: This work demonstrates that optimum conditions for OTA production are very different from those for growth. While growth rates differed significantly between strains, integration of the OTA production data suggests possible benefits for use of the information on a regional basis. Significance and Impact of the Study: Very little detailed information has previously been available on the ecology of A. carbonarius. This knowledge is critical in the development and prediction of the risk models of contamination of grapes and grape products by this species under fluctuating and interacting environmental parameters.

R . H O P E , D . A L D R E D A N D N . M A G A N . 2005.Aims: Comparisons were made of the effect of water activity (a w 0AE99-0AE85), temperature (15 and 25°C) and time (40 days) on growth/production of the trichothecene mycotoxin deoxynivalenol (DON) by Fusarium culmorum and Fusarium graminearum on wheat grain. Methods and Results: Studies examined colonization of layers of wheat grain for 40 days. Fusarium culmorum grew optimally at 0AE98 a w and minimally at 0AE90 a w at 15 and 25°C. Colonization by F. graminearum was optimum at 0AE99 a w at 25 and 0AE98 a w at 15°C. Overall, temperature, a w and their interactions significantly affected growth of both species. Production of DON occurred over a much narrower range (0AE995-0AE96 a w ) than that for growth. Optimum DON was produced at 0AE97 and 0AE99 a w at 15 and 25°C, respectively, by F. culmorum, and at 0AE99 a w and 15°C and 0AE98 a w at 25°C for F. graminearum. Statistically, one-, two-and three-way interactions were significant for DON production by both species. Conclusions: This suggests that the ecological requirements for growth and mycotoxin production by such species differ considerably. The two-dimensional profiles on grain for DON production by these two species have not been examined in detail before. Significance and Impact of the Study: This type of information is essential for developing climate-based risk models for determining the potential for contamination of cereal grain with this trichothecene mycotoxin. It will also be useful information for monitoring critical control points in prevention of such toxins entering the wheat production chain.

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Spatial patterns in carbon (C) and nitrogen (N) cycles of high‐latitude catchments have been linked to climate and permafrost and used to infer potential changes in biogeochemical cycles under climate warming. However, inconsistent spatial patterns across regions indicate that factors in addition to permafrost and regional climate may shape responses of C and N cycles to climate change. We hypothesized that physical attributes of catchments modify responses of C and N cycles to climate and permafrost. We measured dissolved organic C (DOC) and nitrate (NO3−) concentrations, and composition of dissolved organic matter (DOM) in 21 streams spanning boreal to arctic Alaska, and assessed permafrost, topography, and attributes of soils and vegetation as predictors of stream chemistry. Multiple regression analyses indicated that catchment slope is a primary driver, with lower DOC and higher NO3− concentration in streams draining steeper catchments, respectively. Depth of the active layer explained additional variation in concentration of DOC and NO3−. Vegetation type explained regional variation in concentration and composition of DOM, which was characterized by optical methods. Composition of DOM was further correlated with attributes of soils, including moisture, temperature, and thickness of the organic layer. Regional patterns of DOC and NO3− concentrations in boreal to arctic Alaska were driven primarily by catchment topography and modified by permafrost, whereas composition of DOM was driven by attributes of soils and vegetation, suggesting that predicting changes to C and N cycling from permafrost‐influenced regions should consider catchment setting in addition to dynamics of climate and permafrost.

Aims:To examine the effect of interactions between water, temperature and gas composition on growth and ochratoxin A (OTA) production by isolates of Penicillium verrucosum in vitro and in situ on grain-based media and wheat grain. Methods and Results: Three isolates of P. verrucosum were examined in relation to radial growth rate and OTA production, and to interacting conditions of water activity (a w ), temperature and gas composition on a milled wheat medium. Subsequently, detailed temporal studies were carried out on gamma irradiated wheat grain over the range 0AE75-0AE995 a w , 10-25°C and air, 25 or 50% CO 2 . This showed that optimum growth of P. verrucosum was at 0AE98 a w in vitro at 25°C, but at 0AE95 a w and 25°C on wheat grain. The a w minimum for growth was about 0AE80 a w , although no OTA was produced under this condition even after 56 days. Significant inhibition of growth and OTA production occurred with 50% CO 2 , and 0.90-0AE995 a w at 25°C. Conclusions: The optimum and marginal conditions for growth and OTA production on wheat grain have been identified. At least 50% CO 2 is needed to inhibit growth and OTA production by >75% in moist grain (0AE90-0AE995 a w ). Significance and Impact of the Study: First detailed identification of optimal and marginal interacting conditions of water/temperature and gas composition on growth and OTA production by P. verrucosum on wheat grain. This is a critical component of the postharvest management strategy for minimizing contamination by this important mycotoxin and predicting risk, based on environmental conditions, during drying and storage.