Influence of H 2 O 2 -Induced Oxidative Stress on In Vitro Growth and Moniliformin and Fumonisins Accumulation by Fusarium proliferatum and Fusarium subglutinans .

Fusarium proliferatum and Fusarium subglutinans are common pathogens of maize which are known to produce mycotoxins, including moniliformin (MON) and fumonisins (FBs). Fungal secondary metabolism and response to oxidative stress are interlaced, where hydrogen peroxide (H ₂ O ₂ ) plays a pivotal role in the modulation of mycotoxin production. The objective of this study is to examine the effect of H ₂ O ₂ -induced oxidative stress on fungal growth, as well as MON and FBs production, in different isolates of these fungi. When these isolates were cultured in the presence of 1, 2, 5, and 10 mM H ₂ O ₂ , the fungal biomass of F. subglutinans isolates showed a strong sensitivity to increasing oxidative conditions (27-58% reduction), whereas F. proliferatum isolates were not affected or even slightly improved (45% increase). H ₂ O ₂ treatment at the lower concentration of 1 mM caused an almost total disappearance of MON and a strong reduction of FBs content in the two fungal species and isolates tested. The catalase activity, surveyed due to its crucial role as an H ₂ O ₂ scavenger, showed no significant changes at 1 mM H ₂ O ₂ treatment, thus indicating a lack of correlation with MON and FB changes. H ₂ O ₂ treatment was also able to reduce MON and FB content in certified maize material, and the same behavior was observed in the presence and absence of these fungi, highlighting a direct effect of H ₂ O ₂ on the stability of these mycotoxins. Taken together, these data provide insights into the role of H ₂ O ₂ which, when increased under stress conditions, could affect the vegetative response and mycotoxin production (and degradation) of these fungi.