Abstract
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 (H2O2) plays a pivotal role in the modulation of mycotoxin production. The objective of this study is to examine the effect of H2O2-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 H2O2, 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). H2O2 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 H2O2 scavenger, showed no significant changes at 1 mM H2O2 treatment, thus indicating a lack of correlation with MON and FB changes. H2O2 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 H2O2 on the stability of these mycotoxins. Taken together, these data provide insights into the role of H2O2 which, when increased under stress conditions, could affect the vegetative response and mycotoxin production (and degradation) of these fungi.
Highlights
Moniliformin (MON) is an “emerging mycotoxin” with low molecular weight, mainly produced by several Fusarium species [1,2]
The estimation of fungal growth at different temperatures was performed by measuring the radial growth on PDA plates for both Fusarium species at temperatures ranging from 15–40 ◦C (Figure 1)
The behavior of F. proliferatum at mild temperature was rather similar among isolates, with an optimal growth observed for each at 25–30 ◦C; when temperature increased to 40 ◦C, only the PRO1 isolate actively grew
Summary
Moniliformin (MON) is an “emerging mycotoxin” with low molecular weight, mainly produced by several Fusarium species [1,2]. Due to climate change and the temperature rise, the risk of mycotoxins produced by Fusarium spp. is expected to increase in the coming decades [9,10], involving the toxins produced by Fusarium proliferatum and F. subglutinans At present, these two pathogens can be isolated under Southern European climate conditions, but the range of environments suitable for them to survive and colonize kernels is quite wide [11,12]. These two pathogens can be isolated under Southern European climate conditions, but the range of environments suitable for them to survive and colonize kernels is quite wide [11,12] This characteristic, together with the aforementioned consequences of climatic changes, leads to the reasonable prevision of the spread of F. proliferatum and F. subglutinans toward Northern European regions, with a increased risk of MON and FBs contaminations. In a variety of plants, mycotoxin production has been reported to be promoted by heat and drought stress [18,19], with a close connection between them, as there is some evidence that drought stress aggravation is just a consequence of the more conducive heat stress [18]
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