Characterization of fumonisin toxicity in orally and intravenously dosed swine

Fumonisin B₁ (FB₁), a recently identified mycotoxin produced by Fusarium moniliforme in corn, has been shown to cause death in swine due to pulmonary edema, an apparently species specific effect, and to interfere with sphingolipid metabolism in vitro. Here we characterize the toxicity of fumonisins, using female cross-bred swine weighing 6 to 13 kg, and present a hypothesis regarding the mechanism of fumonisin-induced pulmonary edema in swine. FB₁ was given daily intravenously (IV) to pig 1 for 9 days for a total of 72 mg (7.9 mg/kg) and to pig 2 for 4 days for a total of 67 mg (4.6 mg/kg). Pig 3 (control) was given saline IV for 9 days. Corn screenings naturally contaminated with FB₁ (166 ppm) and FB₂ (48 ppm) were fed to pigs 4, 5, and 6, and ground corn was fed to pigs 7 and 8 (controls). Pigs 4 and 7 were killed on day 5; pig 5 was found dead on day 6; and pigs 6 and 8 were killed on day 15. Pigs 4 and 5 had ingested 187 and 176 mg total fumonisins, respectively, while pig 6 had ingested 645 mg. Feed consumption had decreased in pigs fed corn screenings, with an additional sharp decrease prior to onset of clinical signs. Increases in serum liver enzymes, total bilirubin, and cholesterol were present, but electrocardiograms, heart rate, and body temperature were unaffected. Pigs dosed IV with FB₁, developed mild intermittent respiratory abnormalities, while those fed screenings developed respiratory distress within 5 days. Mild interstitial pulmonary edema was observed in pig 1. Severe interstitial pulmonary edema, pleural effusion, and increased lung wet/dry weight ratio were observed in pigs 4 and 5. All pigs given fumonisin (either IV or orally) had hepatic changes characterized by hepatocyte disorganization and necrosis; pancreatic acinar cell degeneration was also observed. Ultrastructural changes in orally dosed swine included loss of sinusoidal hepatocyte microvilli; membranous material in hepatic sinusoids; and multilamellar bodies in hepatocytes, Kupffer cells, pancreatic acinar cells and pulmonary macrophages. Pulmonary intravascular macrophages (PIMs) contained large amounts of membranous material. Thus, the target organs of fumonisin in the pig are the lung, liver, and pancreas. At lower doses, slowly progressive hepatic disease is the most prominent feature, while at higher doses, acute pulmonary edema is superimposed on hepatic injury and may cause death. We hypothesize that altered sphingolipid metabolism causes hepatocellular damage resulting in release of membranous material into the circulation. This material is phagocytosed by the PIMs thus triggering the release of mediators which ultimately results in pulmonary edema.Presented in part at the 1991 Annual Meeting of the Society of Toxicology. The Toxicologist 11: 143 (A499).     

Experimental reproduction of ELEM

An experiment to gain insight into the minimum toxic dose of fumonisins was conducted by feeding ponies rations with known fumonisin concentrations. Naturally contaminated corn screenings (CS) were blended with pellets, corn, and molasses to formulate individual daily diets. One group of 4 ponies was fed a ration with fumonisin B₁ (FB₁) varying from <1 ppm to 22 ppm. A second group of 5 ponies was fed a ration at varying rates containing 8 ppm FB₁ for 180 days. A panel of clinical chemistry parameters was evaluated twice weekly for both groups. One pony in the first group died of equine leukoencephalomalacia (ELEM) after 225 days of which the final 55 days' diet contained 22 ppm FB₁. Approximately 9 days prior to death, this animal experienced elevated liver chemistry values. All 5 ponies in the second group experienced mild, transient, clincal signs; were euthanized at 180 days; and had mild, histopathological brain lesions.     

Temporal and dose-response features in swine fed corn screenings contaminated with fumonisin mycotoxins

Fumonisin B₁ (FB₁), a mycotoxin produced byFusarium moniliforme andF. proliferatum, induces liver damage and pulmonary edema in swine. We examined the temporal and dose-response features of FB₁ toxicosis in male weanling crossbred pigs fed nutritionally balanced diets, containing corn screenings naturally contaminated with fumonisins, for 14 days. Total fumonisins (FB₁ and FB₂) in diets 1 through 6 were assayed at 175, 101, 39, 23, 5, and <1 ppm (below detectable concentrations), respectively. Clinical signs, serum biochemical alterations, and morphologic changes were evaluated. Pigs were weighed, and bled for hematologic and clinical chemistry evaluation on days 5 and 14. They were euthanized on day 14, or earlier if respiratory distress was observed. Respiratory distress developed in 3/5 pigs fed diet 1 between days 4 and 6 due to severe pulmonary edema and pleural effusion. Histologic evidence of hepatic injury was present in all pigs fed diets 1 and 2, 3/5 on diet 3, and 1/5 on diet 4. Serum bilirubin and cholesterol concentrations, gamma-glutamyl transferase (GGT), alkaline phosphatase (ALP), alanine aminotransferase (ALT), aspartate aminotransferase (AST), and arginase (ARG) activities were elevated in pigs fed diets 1 and 2. Based on liver histopathology, the no observed adverse effect level (NOAEL) for fumonisin toxicity in swine was <23 ppm total fumosins for the 14-day period. Based on regression analyses of the clinical chemistry profiles at 14 days, the NOAEL was <12 ppm, with ALP being the most sensitive parameter. In conclusion, pulmonary edema occurred only at the highest fumonisin concentration (175 ppm), while liver damage occurred at much lower concentrations with a NOAEL of <12 ppm.Abbreviations ALP alkaline phosphatase - ALT alanine aminotransferase - ARG arginase - AST aspartate aminotransferase - ELEM equine leukoencephalomalacia - FB₁ fumonisin B₁ - GGT gamma-glutamyl transferase - NOAEL no observed adverse effect level     

A review and update of animal toxicoses associated with fumonisin-contaminated feeds and production of fumonisins by Fusarium isolates

During the 1989 corn harvest season, numerous reports of equine leukoencephalomalacia (ELEM) outbreaks and a pulmonary edema (PPE) syndrome in swine from several regions of the United States were received by the National Veterinary Services Laboratories (NVSL), Ames, Iowa. Previous and concurrent research linked Fusarium moniliforme and fumonisin-contaminated feeds to both diseases. Chemical and mycological investigations revealed fumonisin B₁ (FB₁) concentrations of 20 to 360 ppm in suspect swine feeds and 8 to 117 ppm in suspect equine feeds. Nonproblem feeds contained concentrations below 8 ppm. Fusarium moniliforme and Fusarium proliferatum were isolated from both problem and nonproblem equine and swine feeds. When cultured on autoclaved corn, the F. moniliforme and F. proliferatum isolates produced respective FB₁ and fumonisin B₂ (FB₂) that range from less than 5 to more than 2450 ppm and less than 5 to more than 1000 ppm, respectively. Isolates from both problem and nonproblem feeds produced high levels (greater than 500 ppm) in culture. Reported here is a review of chemical and mycological data resulting from the study of several cases of PPE and ELEM.     

In vivo and in vitro electrophysiological monitoring of rat neocortical activity after dietary fumonisin exposure

Corn pellets, containing 30 mg/kg bw/day fumonisin B₁ (FB₁) or containing no FB₁ were fed in two series of experiments to rats. Spontaneous and evoked potentials were measured in the neocortex both in vivo and in vitro in “corn fed control” rats and in rats after a five day dietary exposure to FB₁. The FB₁ content of corn was quantitated by HPLC. Auditory evoked potentials recorded in vivo on freely moving animals after feeding a corn diet containing FB₁ for 5 days revealed a highly significant 20–60% decrease in the primary and mid-latency components; cortex slices in vitro showed a reduced excitability both in standard artificial cerebrospinal fluid (ACSF) solution and in a 4-aminopyridine induced epilepsy model. Spontaneous epileptic discharges after FB₁ exposure had an increased latency, decreased frequency, longer duration and modified signal forms. Altered excitability and seizure susceptibility of the neocortex after fumonisin exposure are suspected to be associated with modified signal transmission. These changes may be due to concurrent effects of possible liver and renal toxicity or partly of nutritional deficiencies. This revised version was published online in June 2006 with corrections to the Cover Date.     

Determination of baseline susceptibility to Cry1Ab protein for Asian corn borer (Lep., Crambidae)

Abstract: Although transgenic Bacillus thuringiensis (Bt) corn can provide a new tool for control of the Asian corn borer (ACB), Ostrinia furnacalis (Guenée), concern has been raised regarding the possibility of the target insect evolving resistance to the Bt protein under intensive selection pressure from Bt corn. Therefore, it is necessary to establish baseline data to enable detection of changes in susceptibility in field populations after prolonged exposure to Bt corn. Susceptibility to purified Cry1Ab protein from Bt was determined for 10 populations of ACB from the major corn‐growing regions of China, ranging geographically from Heilongjiang Province in the northeast to Shaanxi Province in the east‐central part. Neonate ACB were exposed to semi‐artificial diet incorporated with increasing Cry1Ab protein concentrations, and mortality and growth inhibition were evaluated after 7 days. The range of LC₅₀ (50% lethal concentration) among the populations was 0.10 to 0.81 μg/g (Cry1Ab protein/diet). Differences (P < 0.05) in susceptibility among the populations were significant. LC₅₀s generated from the Huanghuaihai Summer Corn Region were higher than those from the Spring Corn Regions. Bt was one of the significant natural biomortality factors of overwintering generation ACB. There was a significant correlation between percentage of the larvae infected with Bt and their LC₅₀ values to Cry1Ab protein in geographic distinct populations (r = 0.7350*, d.f. = 8, _r0.05 = 0.632). Based on the background of Bt formulations used for corn insect pests control in these areas, these differences were not caused by prior exposure to Bt insecticides. Instead, the small differences likely reflect natural Bt selection pressure. Because the variation in susceptibility to Cry1Ab was small (<10‐fold), the ACB apparently is susceptible to Cry1Ab across its range within China.     

Resistance of sugarcane borer to Bacillus thuringiensis Cry1Ab toxin

The sugarcane borer, Diatraea saccharalis (F.) (Lepidoptera: Crambidae), strain (F52‐3‐R) was developed from F₃ survivors of a single‐pair mating on commercial Cry1Ab Bacillus thuringiensis (Bt) corn plants in the greenhouse. The susceptibility of a Bt‐susceptible and the F52‐3‐R strain of D. saccharalis to trypsin‐activated Cry1Ab toxin was determined in a laboratory bioassay. Neonate‐stage larvae were fed a meridic diet incorporating Cry1Ab toxin at a concentration range of 0.0625 to 32 µg g^?1. Larval mortality, larval weight, and number of surviving larvae that did not gain significant weight (<0.1 mg per larva) were recorded on the 7th day after inoculation. The F52‐3‐R strain demonstrated a significant level of resistance to the activated Cry1Ab toxin. Larval mortality of the Bt‐susceptible strain increased in response to higher concentrations of Cry1Ab toxin, exceeding 75% at 32 µg g^?1, whereas mortality of the F52‐3‐R strain was below 8% across all Cry1Ab concentrations. Using a measure of practical mortality (larvae either died or gained no weight), the median lethal concentration (LC₅₀) of the F52‐3‐R strain was 102‐fold greater than that of the Bt‐susceptible insects. Larval growth of both Bt‐susceptible and F52‐3‐R strains was inhibited on Cry1Ab‐treated diet, but the inhibition of the F52‐3‐R strain was significantly less than that of the Bt‐susceptible insects. These results confirm that the survival of the F52‐3‐R strain on commercial Bt corn plants was related to Cry1Ab protein resistance and suggest that this strain may have considerable value in studying resistance management strategies for Bt corn.     

Production of fumonisins B1, B2 and B3 byFusarium proliferatum Isolated from rye grains

Using the seed- plate technique, we have isolated a strain ofF. proliferatum from rye grains that produces 3 fumonisins, fumonisin B₁ (FB₁), FB₂ and FB₃ on inoculated rice and corn. Inoculated corn and rice were extracted with an aqueous methanol solution and fumonisin concentrations estimated using high performance liquid chromatography. Production of all 3 fumonisins (FB₁, FB₂ and FB₃) was much higher on rice than corn; ranging from 3816, 1068 and 985 ppm to 1643, 350 and 162 ppm respectively. We conclude that all natural substrates whereF. proliferatum is present as a component of the mycoflora should be monitored for the presence of fumonisins.     

Mutagenic potentials of fumonisin contaminated corn following ammonia decontamination procedure

Naturally contaminated corn implicated in an outbreak of equine leukoencephalomalacia (ELEM) in southeastern Arizona was analyzed for mutagenic potential using the Salmonella/microsome mutagenicity assay before and after treatment with the ammonia procedure. Crude acetonitrile: water (1+1) extracts of high-pressure/ambient temperature (HP/AT) ammonia decontaminated, HP/AT plus low pressure/high temperature (LP/HT), and non-ammoniated fumonisin contaminated corn were tested for mutagenic potentials. Relatively pure (approx. 90%) fumonisin B₁ standard was also tested for comparison purposes. The results of this experiment indicate that there was no mutagenic potential for the fumonisin B₁ standard at the concentrations tested (100 g/plate). Also, neither the naturally-contaminated corn nor the ammonia decontaminated samples elicited a positive mutagenic response. Fumonisin B₁ levels, as determined by HPLC methods, were reduced by an average of 79% via the ammonia decontamination process. It is encouraging to note that, while further work is necessary to increase the efficacy of the ammonia process to reduce fumonisin levels, the ammonia process did reduce fumonisin levels and no mutagenic potentials were apparent in the treated corn.Abbreviations HP/AT high pressure/ambient temperature - LP/HT low pressure/high temperature - ELEM equine leukoencephalomalacia - FB₁ fumonisin B₁ - FB₂ fumonisin B₂     

Occurrence of Aspergillus section Flavi and aflatoxin B1 in corn genotypes and corn meal in Argentina

A study has been carried out in Argentina on samples of corn genotypes from a breeding station as well as in commercially available corn meal. All samples were analyzed for fungal infection and aflatoxin B₁.Mycological analysis of corn genotypes showed the presence of three principal genera of filamentous fungi Fusarium (100%), Penicillium (67%) and Aspergillus (60%). In the genus Fusarium three species were identified, F. moniliforme (42%), F. nygamai (56%) andF. proliferatum (1.8%). Eight species ofPenicillium were identified, the predominant species isolated were P. minioluteum, P. funiculosum and P. variabile. In the genus ranked third in isolation frequency, two species were identified, A. flavus and A. parasiticus, the percentage of infection was 78% and 21%, respectively. Only one corn genotype was contaminated with aflatoxin B₁ at a level of 5 ppb. The cornmeal samples showed great differences in fungal contamination, the values ranging from 1 × 10¹ to 7 × 10⁵ cfu g^–1. Fusarium (68%), Aspergillus (35%) and Penicillium (21%) were the most frequent genera isolated. Among the genus, Aspergillus, A. parasiticus (38%) was the most frequent species isolated. All the samples of corn meal were negative to aflatoxin B₁. These results indicate a low degree of human exposure to aflatoxins in Argentina through the ingestion of maize or corn meal.This revised version was published online in October 2005 with corrections to the Cover Date.     

Production of fumonisins byFusarium species of Taiwan

Twenty-nineFusarium species isolated from various sources in different districts of Taiwan were tested for their ability to produce fumonisins in corn cultures. OnlyFusarium moniliforme produced fumonisin B₁ (FB₁) and fumonisin B₂ (FB₂). The finding that the other 28Fusarium species produced neither FB₁ nor FB₂ is preliminary because only one strain per species was studied. The detection of FB₁ and FB₂ in cultures ofF. moniliforme was demonstrated by TLC and HPLC, and FB₁ was further confirmed by mass spectrometry. In a separate experiment, in which 38 strains ofF. moniliforme were tested for fumonisins, approximately 66% (25/38) produced FB₁ and/or FB₂. Of the 25 strains, 14 produced only FB₁ and 11 produced both FB₁ and FB₂, and the amounts of FB₁ and FB₂ produced by different strains varied greatly. This is the first report that fumonisins are found in corn cultures experimentally infected withF. moniliforme strains from Taiwan. It is safe to assume that fumonisin producing strains ofF. moniliforme are widely distributed among the economic crops such as corn, rice, sugarcane, and sorghum throughout the Island.Abbreviations FB₁ Fumonisin B₁ - FB₂ Fumonisin B₂ - OPA o-phthalidialdehyde     

Determination of mycobiota and mycotoxins in pig feed in central Argentina

Aims: To evaluate the mycobiota and natural levels of aflatoxins, fumonisins and zearalenone present in compound feed and home‐corn grains intended for fattening pigs. Methods and Results: Total fungi, Fusarium and Aspergillus species occurrence were examined. Aflatoxins and zearalenone were detected by thin‐layer chromatography and fumonisins by high‐pressure liquid chromatography. Fungal counts were generally higher than 1 × 10⁵ colony forming units (CFU) ml^?1. Aspergillus flavus, Aspergillus parasiticus and Fusarium verticillioides were the most prevalent species. FB₁ and FB₂ were detected in all feed and corn samples. Aflatoxin B₁ was detected in 33·33% of initial and growing feed and in 44·44% of final feed samples. It was not detected in corn samples. All feed and corn samples were negative for AFB₂, AFG₁, AFG₂ and ZEA presence during all growing stages tested. Conclusions: Fungal counts at all growing periods exceeded the levels proposed as feed hygienic quality limits. Aflatoxin levels in all feeds and fumonisin levels in many samples were higher than the established regulations. Significance and Impact of the Study: The presence of mycotoxins indicates the existence of contamination. This fact requires periodic monitoring to prevent the occurrence of mycotoxicosis in animal production, to reduce the economic losses and to minimize hazards to human health.     

Binding of 45Ca2+ to particulate fractions of coleoptile tissue

Summary Using recently developed techniques, we have investigated the binding of ⁴⁵Ca²⁺ to membrane preparations from corn (Zea mays L) and oat (Avena sativa L) coleoptile tissue. Scatchard plot analysis reveals at least two Ca²⁺-binding sites in each tissue, a high affinity binding site (K _m=7.7×10^-7 M, n=6.9×10^-10 mol·0.5 g f.w.^-1 in corn, K _m=4.93×10^-6 M, n=2.29×10^-9 mol·0.5 g f.w.^-1 in Avena) and a low affinity binding site (K _m=9.01×10^-5 M, n=5.4×10^-8 mol·0.5 g f.w.^-1 in corn; K _m=1.03×10^-4 M, n=3.40×10^-8 mol·0.5 g f.w.^-1 in Avena). There is also some evidence of a third, lower affinity binding site in each tissue, especially corn.More detailed studies with corn coleoptile homogenates show that they contain a potent dialyzable inhibitor of Ca²⁺ binding. Monovalent cations were observed to be ineffective as inhibitors of Ca²⁺ binding in corn. However, of six divalent cations tested, all were capable of strong inhibition of Ca²⁺-binding and there appeared to be a relationship between size of the atomic radius of the ion and potency as an inhibitor of calcium binding.Abbreviations CSM corn suspensiom medium - EDC 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide - GEE glycine ethyl ester     

Effects of pH on the in Vitro Sorption of Mutagens to Dietary Fibers

Dietary fibers, alginate and defatted corn fiber, sorbed food mutagens, Trp-P-1 and Glu-P-1, which are heterocyclic amines formed in the cooking process. The sorption behavior of the heterocyclic amines to defatted corn fiber and alginates was analyzed under pH-controlled conditions. Glu-P-1 and alginic acid had pK_a values of 4.2 and 3.6, respectively, whereas Trp-P-1, which showed alkaline in solution, possessed two pK_a values of 4.8 and 7.7. Defatted corn fiber, which was mainly composed of cellulose and hemicellulose, did not show a significant pK_a value. The amount of sorbed Trp-P-1 to the alginates increased as the pH value of the buffer was elevated, and was much more than that sorbed to defatted corn fiber at each pH condition. These results suggest that the alginates held the amino group of Trp-P-1 or Glu-P-1 on their carboxyl group as a cation exchanger.     

Subchronic toxicological investigations of Fusarium moniliforme-contaminated corn,culture material,and ammoniated culture material

The fungus Fusarium moniliforme is ubiquitous on corn throughout the world and is a likely co-contaminant on corn infested with aflatoxin-producing Aspergillus flavus. Ammoniation has been used to detoxify aflatoxin-contaminated commodities. To determine the effect of ammoniation on the toxic potential of Fusarium moniliforme, male Sprague-Dawley rats were fed either diets containing 10% sound corn, ammoniated corn, corn culture material of hepatotoxic F. moniliforme strain MRC 826 (CM), or ammoniated CM for four weeks. They were observed for signs of toxicity and hematological, serum chemical and histopathological evaluations were made. Groups of male Balb/c mice were fed diets fortified with 10% sound corn or CM for four weeks and evaluated by serum chemical and histopathological means to determine the suitability of mice as a model species for investigation of F. moniliforme-induced hepatotoxicity. Ammoniation was ineffective for detoxification of the CM. Hepatotoxicity and renal toxicity of CM and ammoniated CM were qualitatively similar, although renal tubular lesions appeared more advanced in rats fed ammoniated CM. Adrenal cortical cellular vacuolation was also found in CM and ammoniated CM-fed rats, while focal seminiferous tubular degeneration and aspermia were found only in the testes of ammoniated CM-fed rats. Fumonisin B₁ concentrations of the CM and ammoniated CM diets averaged 99 and 75 ppm, respectively. CM containing 99 ppm fumonisin B₁ also produced hepatotoxicity in mice similar to that found in CM-fed rats. Thus, mice may be useful for investigations of F. moniliforme-induced hepatotoxicity.Mention of a trademark, proprietary name or vendor does not imply its approval by the US Department of Agriculture to the exclusion of others that may also be suitable.     

Susceptibility of northern corn rootworm Diabrotica barberi (Coleoptera: Chrysomelidae) to mCry3A and eCry3.1Ab Bacillus thuringiensis proteins

The susceptibility of the northern corn rootworm Diabrotica barberi (Smith & Lawrence) to mCry3A and eCry3.1Ab proteins derived from Bacillus thuringiensis (Bt) was determined using a diet bioassay. Northern corn rootworm neonates were exposed to different concentrations of mCry3A and eCry3.1Ab, incorporated into artificial diet. Larval mortality was evaluated after 7 d. The mCry3A and eCry3.1Ab proteins were found to be toxic to the northern corn rootworm larvae. The LC₅₀ and LC₉₉ values for mCry3A were 5.13 and 2482.31 μg/mL, respectively. For eCry3.1Ab, the LC₅₀ and LC₉₉ values were 0.49 and 213.01 μg/mL. Based on the estimated lethal concentrations, eCry3.1Ab protein was more efficacious to northern corn rootworm larvae than mCry3A. These lethal concentration values will be used as diagnostic doses for routine annual monitoring for change in susceptibility of field collected northern corn rootworm to mCry3A, and eCry3.1Ab toxins.     

Susceptibility of Cry1Ab-resistant and -susceptible sugarcane borer (Lepidoptera: Crambidae) to four Bacillus thuringiensis toxins

Sugarcane borer, Diatraea saccharalis (F.), is a primary corn stalk borer pest targeted by transgenic corn expressing Bacillus thuringiensis (Bt) proteins in many areas of the mid-southern region of the United States. Recently, genes encoding for Cry1A.105 and Cry2Ab2 Bt proteins were transferred into corn plants (event MON 89034) for controlling lepidopteran pests. This new generation of Bt corn with stacked-genes of Cry1A.105 and Cry2Ab2 will become commercially available in 2009. Susceptibility of Cry1Ab-susceptible and -resistant strains of D. saccharalis were evaluated on four selected Bt proteins including Cry1Aa, Cry1Ac, Cry1A.105, and Cry2Ab2. The Cry1Ab-resistant strain is capable of completing its larval development on commercial Cry1Ab-expressing corn plants. Neonates of D. saccharalis were assayed on a meridic diet containing one of the four Cry proteins. Larval mortality, body weight, and number of surviving larvae that did not gain significant weight (<0.1 mg per larva) were recorded after 7 days. Cry1Aa was the most toxic protein against both insect strains, followed in decreasing potency by Cry1A.105, Cry1Ac, and Cry2Ab2. Using practical mortality (larvae either died or no significant weight gain after 7 days), the median lethal concentration (LC₅₀) of the Cry1Ab-resistant strain was estimated to be >80-, 45-, 4.1-, and −0.5-fold greater than that of the susceptible strain to Cry1Aa, Cry1Ac, Cry1A.105 and Cry2Ab2 proteins, respectively. This information should be useful to support the commercialization of the new Bt corn event MON 89034 for managing D. saccharalis in the mid-southern region of the United States.     

Survival and oviposition of a western corn rootworm variant feeding on soybean

The role of soybean, Glycine max (L.) Merril (Fabaceae), in the circumvention of crop rotation was evaluated by observing the effects of soybean herbivory on western corn rootworm, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae) survival and oviposition. Field collected D. virgifera adults resistant to annual rotation of corn, Zea mays (L.) (Poaceae), and soybean were given the opportunity to feed on a soybean pre‐treatment diet prior to diet combinations of corn, soybean, and/or water. The number of days that the adults survived after removal of the diet combinations was used as a measure of insect vigor and diet quality. Willingness to feed on a soybean foliage pre‐treatment did not indicate greater ability to benefit nutritionally from soybean herbivory. Adult D. virgifera previously feeding on corn, soybean, or water survived starvation for 8.3 ± 0.15 days, 5.1 ± 0.13 days, and 3.9 ± 0.14 days, respectively. Diabrotica virgifera recover from 2 days of starvation or poor diet if subsequently given access to corn tissues for 2 days. Eggs were laid within 1 day of access to poor diet or starvation. Other D. virgifera, captured as they flew from a cornfield into a soybean field, were maintained on soybean foliage or only water until they died. Of the beetles with access to soybean foliage, 24% fed within 24 h after capture and survived 1 day longer than insects given only water. Only 20% of these D. virgifera were able to lay eggs without consuming additional corn prior to death. Few D. virgifera enter soybean fields capable of immediate oviposition. Female reproductive status and diet quality influence the likelihood of oviposition following exposure to stress. The effects of soybean herbivory may contribute to the proximate mechanism of resistance to crop rotation.     

The relationship betweenPleurotus ostreatus andAspergillus flavus and the production of aflatoxin

The relationship betweenPleurotus ostreatus andAspergillus flavus in common mixed culture on various substrates was investigated. It was found thatP. ostreatus, similarly to some other higher fungi, can liquidate coloniesof A. flavus. This fungus does not produce aflatoxin and chromatographically similar compounds. On straw, corn cobs, millet and wheatA. flavus produced aflatoxin after a 3-week cultivation. A subsequent cultivation of P.ostreatus led to detoxication of straw and corn cobs but millet and wheat were not detoxicated. Cultivation of P.ostreatus in the presence of 40–100 μg of aflatoxin B₁ per g substrate did not result in detoxication of the material even after 34 d but the results showed that the aflatoxin concentration decreased to about one-fourth of the added amount.