The production of fumonisins, fusaproliferin and beauvericin by Gibberella fujikuroi different mating populations isolated from maize in Argentina was evaluated. From 203 strains of Fusarium verticillioides (G. fujikuroi mating population A), 193 were fumonisin producers. Among members of mating population A, female fertile strains produced 20% more toxin than female sterile ones. Among 78 Fusarium proliferatum strains (G. fujikuroi mating population D) 65 produced fumonisins. The percentage of strains that were high, intermediate and low level toxin producers varied according to the species evaluated and the area from which the strains were isolated. Fusarium subglutinans (G. fujikuroi mating population E) strains produced low levels or were no fumonisin producers. Strains from both G. fujikuroi mating populations D and E were able to produce fusaproliferin and beauvericin. Among the members of F. subglutinans (G. fujikuroi mating population E) the fusaproliferin production was more constant. Co-production of fumonisin, fusaproliferin and beauvericin among the strains belonging to G. fujikuroi D and E was also observed. The co-production of fumonisin, beauvericin and fusaproliferin in maize need to be considered, since from the toxicological point of view interactions between these toxins could occur. The toxigenic ability of the strains evaluated prompt us that is necessary to determine the natural occurrence of fusaproliferin and beauvericin in Argentinean maize.

The effect of single or mixtures of antioxidants on the lag phase prior to growth, growth rate, hydrolytic enzyme production (N-acetyl-β-glucosaminidase, β-D-glucosidase and α-D-galactosidase) and fumonisin production by Fusarium verticillioides and F. proliferatum was evaluated on maize-based media at 25 °C, and under different water activity (aW) conditions. An increase in the lag phase (h) was observed for both F. verticillioides and F. proliferatum especially with propyl paraben (PP)+butylated hydroxyanisole (BHA) treatments at all aW levels tested. For both species PP alone or in combination with BHA, at concentrations of 0.5 and 1 mM reduced the growth rates by > 85% at the three aW levels tested (0.995; 0.98 and 0.95). PP+butylated hydroxytoluene (BHT) or trihydroxybutyrophenone (THBP) were less effective in controlling growth, regardless of aW level. Combinations of PP+BHA reduced the fumonisin concentrations produced by F. verticillioides and F. proliferatum at 0.995 and 0.98 aW significantly. However, at low concentrations of antioxidants (0.5 mM) some stimulation in fumonisin production was observed with some treatments. The efficacy of the treatments was reflected in the impact on enzyme production. In the untreated control the highest total enzyme activity of three hydrolytic enzymes was observed at 0.995 aW after 96 h. All the antioxidant treatments alone or combined resulted in a significant reduction (P < 0.001) of the total enzyme activity at the aW levels tested. Only 10 mM THBP produced an increase in the total amount of N-acetyl-β-D-glucosidase by both F. verticillioides and F. proliferatum. For the three enzymes single factors: time, aW and antioxidant treatments, most two and all three way interactions were significant (P < 0.001). The use of combined mixtures of antioxidants could be a good strategy to diminish the entry of fumonisin into the animal feed and human food chains.

The relation between the pattern of fumonisin production and the mating population and mating type of Fusarium isolates from maize in Argentina at different maturity stages has been evaluated. Fifty-one isolates of Fusarium species belonging to the Liseola section were identified to mating population and tested for their ability to produce fumonisins (FB1, FB2 and FB3). Only mating populations associated with maize, A (Fusarium moniliforme, 23 isolates), D (F. proliferatum, 24 isolates) and E (F. subglutinans, 4 isolates) were found. All but two isolates of populations A and D produced, when grown on maize substrate, high levels of fumonisins ranging from 0·01 to 3·99 mg g−1 (mean 2·00 mg g−1 and 1·69 mg g−1, respectively), whereas isolates of population E yielded less than 0·02 mg g−1 (mean 0·01 mg g−1). Five isolates of F. proliferatum, all belonging to mating type D−, produced more FB2, than FB1, which is consistent with finding a relatively large amount of FB2 (0·01 mg g−1; FB2/FB1=2·27) in one of the maize samples from which these isolates were obtained. Amounts of FB3 were similar to FB2 in cultures of mating population A (mean FB3/FB2=0·89), but much lower than FB2 in cultures of mating population D (mean FB3/FB2=0·21).