This review of Fusarium ear blight (scab) of small grain cereals has shown that up to 17 causal organisms have been associated with the disease, which occurs in most cereal-growing areas of the world. The most common species were Fusarium graminearum (Gibberella zeae), F. culmorum, F, avenaceum (G, avenacea), F, poae and Microdochium nivale (Monographella nivalis). The disease was recorded most frequently under hot, wet climatic conditions where significant yield losses and mycotoxin accumulation in grain were reported. Possible sources of inoculum were reported as crop debris, alternative hosts and Fusarium seedling blight and foot rot of cereals. The mode of dispiersal of inoculum to ears remains unclear, but contaminated arthropod vectors, systemic fungal growth through plants, and wind and rain-splash dispersal of spores have been proposed. Infection of wheat ears was shown to occur mainly during anthesis, and it has been demonstrated that fungal growth stimulants may be present in anthers. Despite the importance of the disease, particularly during epidemic years, control methods are limited. Much effort has gone into breeding resistant wheat varieties and into improving our understanding of the possible mechanisms and genetic basis of resistance, with only moderate success. There are also surprisingly few reports of successful fungicidal or biological control of the disease in the field.

Fusarium ear blight (scab) in small grain cereals—a review

Indoor air quality and health

Trichothecene mycotoxins are a group of structurally similar fungal metabolites that are capable of producing a wide range of toxic effects. Deoxynivalenol (DON, vomitoxin), a trichothecene, is prevalent worldwide in crops used for food and feed production, including in Canada and the United States. Although DON is one of the least acutely toxic trichothecenes, it should be treated as an important food safety issue because it is a very common contaminant of grain. This review focuses on the ability of DON to induce toxicologic and immunotoxic effects in a variety of cell systems and animal species. At the cellular level, the main toxic effect is inhibition of protein synthesis via binding to the ribosome. In animals, moderate to low ingestion of toxin can cause a number of as yet poorly defined effects associated with reduced performance and immune function. The main overt effect at low dietary concentrations appears to be a reduction in food consumption (anorexia), while higher doses induce vomiting (emesis). DON is known to alter brain neurochemicals. The serotoninergic system appears to play a role in mediation of the feeding behavior and emetic response. Animals fed low to moderate doses are able to recover from initial weight losses, while higher doses induce more long-term changes in feeding behavior. At low dosages of DON, hematological, clinical, and immunological changes are also transitory and decrease as compensatory/adaptation mechanisms are established. Swine are more sensitive to DON than mice, poultry, and ruminants, in part because of differences in metabolism of DON, with males being more sensitive than females. The capacity of DON to alter normal immune function has been of particular interest. There is extensive evidence that DON can be immunosuppressive or immunostimulatory, depending upon the dose and duration of exposure. While immunosuppression can be explained by the inhibition of translation, immunostimulation can be related to interference with normal regulatory mechanisms. In vivo, DON suppresses normal immune response to pathogens and simultaneously induces autoimmune-like effects which are similar to human immunoglobulin A (IgA) nephropathy. Other effects include superinduction of cytokine production by T helper cells (in vitro) and activation of macrophages and T cells to produce a proinflammatory cytokine wave that is analogous to that found in lipopolysaccharide-induced shock (in vivo). To what extent the elevation of cytokines contributes to metabolic effects such as decreased feed intake remains to be established. Although these effects have been largely characterized in the mouse, several investigations with DON suggest that immunotoxic effects are also likely in domestic animals. Further toxicology studies and an assessment of the potential of DON to be an etiologic agent in human disease are warranted.

Toxicology of deoxynivalenol (vomitoxin).

A review of worldwide contamination of cereal grains and animal feed with Fusarium mycotoxins

Some major mycotoxins and their mycotoxicoses--an overview.

Mycotoxins in grain: compounds other than aflatoxin.

A single isolate of Fusarium graminearum (DAOM 178148) was used to infect experimentally 9 spring wheat, 5 rye and 6 triticale cultivars and the resulting amounts of fungal biomass (determined as ergosterol), deoxynivalenol and other mycotoxins at the same stage of development were compared. Resistant cultivars of wheat, rye and triticale contained low concentrations of deoxynivalenol (mean 0.6 ppm) in the kernels, whereas susceptible cultivars of wheat and triticale contained much higher concentrations (mean 10.2 ppm). The corresponding chaffs contained ca. 8 fold higher concentrations. Higher ergosterol concentrations in the susceptible cultivars showed that these cultivars had lower resistance to hyphal invasion. Ergosterol to deoxynivalenol ratios in the susceptible cultivars averaged ca. 2.4 and were much higher in the resistant, averaging ca. 12 and ca. 240 for the wheat and rye, respectively. The data suggest that resistant cultivars have factors that prevent synthesis and/or promote degradation of deoxynivalenol. Zearalenone was not detected in any sample and 15-acetyldeoxynivalenol was noted only in the chaff of the most susceptible wheat cultivar.



Zusammenfassung

Ein einzelnes Isolat von Fusarium graminearum (DAOM 178148) wurde eingesetzt, um experimentell 9 Sommerweizen-, 5 Roggen- und 6 Triticale Kultivare zu infizieren und die sich ergebenden Mengen pilzlicher Biomasse (bestimmt als Ergosterol), Deoxynivalenol und andere Mycotoxine zum gleichen Entwicklungsstand zu vergleichen. Resistente Kultivare von Weizen, Roggen und Triticale enthielten geringe Konzentrationen von Deoxynivalenol (Durchschnitt 0,6 ppm) in den Kornern, wahrend anfallige Kultivare von Weizen und Triticale wesentlich hohere Konzentrationen (Durchschnitt 10,2 ppm) enthielten. Das entsprechende Stroh enthielt ca. 8mal hohere Konzentrationen. Hohere Konzentration von Ergosterol in den anfalligen Kultivaren zeigten, daβ diese Kultivare eine geringere Resistenz gegenuber der Hypheninvasion hatten. Das Verhaltnis Ergosterol zu Deoxynivalenol in den anfalligen Kultivaren betrug im Durchschnitt ca. 2,4 und war in den Resistenten viel hoher, die im Mittel ca. 12 und 240 fur Weizen bzw. Roggen aufzeigten. Die Ergebnisse lieβen vermuten, daβ die resistenten Kultivare Faktoren enthalten, die die Synthese verhindern und/oder den Abbau von Deoxynivalenol unterstutzen. Zearalenon konnte in keiner Probe gefunden und 15-Acetyldeoxynivalenol konnte nur im Stroh der meisten anfalligen Weizenkultivare festgestellt werden.

J. D. Miller

Papers

Mycotoxins in grain: compounds other than aflatoxin.

Deoxynivalenol and Fusarium Head Blight Resistance in Spring Cereals

Mycotoxins in grain

Diseases in humans with mycotoxins as possible causes.

Health implications of fungi in indoor environments - an overview.