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Aspergillus flavus, a haploid organism found worldwide in a variety of crops, including maize, cottonseed, almond, pistachio, and peanut, causes substantial and recurrent worldwide economic liabilities. This filamentous fungus produces aflatoxins (AFLs) B1and B2, which are among the most carcinogenic compounds from nature, acutely hepatotoxic and immunosuppressive. Recent efforts to reduce AFL contamination in crops have focused on the use of nonaflatoxigenic A. flavus strains as biological control agents. Such agents are applied to soil to competitively exclude native AFL strains from crops and thereby reduce AFL contamination. Because the possibility of genetic recombination in A. flavus could influence the stability of biocontrol strains with the production of novel AFL phenotypes, this article assesses the diversity of vegetative compatibility reactions in isolates of A. flavus to identify heterokaryon self-incompatible (HSI) strains among nonaflatoxigenic isolates, which would be used as biological controls of AFL contamination in crops. Nitrate nonutilizing (nit) mutants were recovered from 25 A. flavus isolates, and based on vegetative complementation between nit mutants and on the microscopic examination of the number of hyphal fusions, five nonaflatoxigenic (6, 7, 9 to 11) and two nontoxigenic (8 and 12) isolates of A. flavus were phenotypically characterized as HSI. Because the number of hyphal fusions is reduced in HSI strains, impairing both heterokaryon formation and the genetic exchanges with aflatoxigenic strains, the HSI isolates characterized here, especially isolates 8 and 12, are potential agents for reducing AFL contamination in crops.

The aim was to evaluate the excretion of residues of aflatoxin B1 (AFB1), aflatoxin M1 (AFM1), aflatoxin B2a (AFB2a) and aflatoxicol (AFL) in eggs of laying Japanese quail fed rations with low levels of aflatoxin B1 for 90 days. The quail were randomly assigned into four experimental groups and given prepared rations containing either 0 (controls), 25, 50 or 100 μg AFB1kg-1 feed. Thirty-two eggs per treatment were collected on days 1-7, 10, 20, 30, 60 and 90 of the aflatoxin treatment period, and submitted to aflatoxin analysis by high-performance liquid chromatography. Average egg production and feed consumption were not affected (p > 0.05) by AFB 1. Egg weight was significantly lower (p <0.05) only for groups exposed to 100 µg AFB1kg-1. Residues of aflatoxins were detected in eggs at levels that ranged from 0.01 to 0.08 µg kg-1 (AFB1), 0.03-0.37 µg kg-1 (AFM1), 0.01-1.03 µg kg-1 (AFB2a) and 0.01-0.03 µg kg-1 (AFL). Results indicate that the excretion of aflatoxin residues in quail eggs might occur at relatively low concentrations under conditions of long-term exposure of quail to low levels of AFB1.

The effect of storage on mycoflora profile was monitored bimonthly in 36 corn (Zea mays L.) samples, dividing the same sample into groups dried to 11 and 14% moisture content (1008 analysis). These groups were further subdivided based on the initial total count (moulds and yeasts) up to 104 CFU g-1 (12 samples, range 1.6 × 104 to 9.0 × 104, mean 3.8 × 104 CFU g-1) and up to 105 CFU g-1 (24 samples, range 1.0 × 105 to 5.0 × 105, mean 2.7 × 105 CFU g-1). In the corn group dried to 11%, the fumonisin content was analysed at the initial stage (freshly harvested) and at the end of 12-month storage. Fusarium spp. and Penicillium spp. prevailed at the freshly harvested stage (100%), maintaining this profile throughout 12 months, in corn dried to both 11 and 14%. Cladosporium spp., Aspergillus spp. and Phoma spp. were also detected at lower frequencies during the storage. Fusarium spp. and the total fungal colony count during 12-month storage carried out with samples dried to 11 or 14% moisture content were statistically evaluated using ANOVA for randomized complete block design. The correlation between storage time and Fusarium spp. and total fungal colony count data was analysed by Pearson's correlation test. There was no difference in Fusarium spp. and total counts in the 104 CFU g-1 initial total count group throughout the storage time (p < 0.05). There was a negative correlation between fungal population and storage time (p < 0.05) in the 105 CFU g-1 initial total count group. Fumonisins were detected in all freshly harvested corn, at a mean concentration of 9.9 ± 6.0 µg g-1 (range 0.74-22.6 μg g-1). These values did not change in the 12-month stored corn (mean of 9.9 ± 5.8 μg g-1, range 0.81-23.7 μg g-1). These post harvest data indicated the importance of moisture content at the crop harvesting/predrying stage to control fungal growth and further fumonisin production.

The effectiveness of the fluorescent viability test (fluorescein diacetate-FDA and ethidium bromide-EB-solution) compared to the plaque counting test (Miles & Misra M & M) was performed on 10 samples of Cryptococcus neoformans cultivated in Sabouraud dextrose agar at 25 °C. The optimum incubation period of 50 minutes was determined. Growth curves of the fungal strains studied based on the mean cell number were drawn for both the FDA & EB and M & M methods. The statistical evaluation (Student's T test) of the average sum of the viable cell counts showed that the FDA-EB method is more sensitive than the M & M test for the studied species. The growth curves of the samples usually followed a homogeneous pattern comparable to other non-dimorphic fungi.