Mycotoxins as antagonistic or supporting agents in the interaction between phytopathogenicFusarium andAlternaria fungi

Abstract

The role of mycotoxins in the microbial competition in an ecosystem or on the same host plant is still unclear. Therefore, a laboratory study was conducted to evaluate the influence of mycotoxins on growth and mycotoxin production of Fusarium and Alternaria fungi. Fusarium culmorum Fc13, Fusarium graminearum Fg23 and two Alternaria tenuissima isolates (At18 and At220) were incubated on wheat kernels supplemented with alternariol (AOH), tetramic acid derivates (TeA), deoxynivalenol (DON) and zearalenone (ZEA) in an in vitro test system. Fungal biomass was quantified by determining ergosterol content. Three Fusarium toxins (DON, nivalenol and ZEA) and three Alternaria toxins (AOH, alternariol methyl ether (AME) and altenuene) were analysed by HPLC-MS/MS. If Alternaria strains grew in wheat kernels spiked with Fusarium mycotoxins, their growth rates were moderately increased, their AOH and AME production was enhanced and they were simultaneously capable of degrading the Fusarium mycotoxins DON and ZEA. In contrast, both Fusarium strains behaved quite differently. The growth rate of Fc13 was not distinctly influenced, while Fg23 increased its growth in wheat kernels spiked with AOH. TeA depressed the ergosterol content in Fc13 as well as in Fg23. The DON production of Fc13 was slightly depressed, whereas the ZEA production was significantly increased. In contrast, Fg23 restricted its ZEA production. Both Fusarium strains were not capable of degrading the Alternaria mycotoxin AOH. Mycotoxins might play an important role in the interfungal competitive processes. They influence growth rates and mycotoxin production of the antagonistic combatants. The observed effects between phytopathogenic Alternaria and Fusarium strains and their mycotoxins aid the understanding of the complexity of microbial competitive behaviour in natural environments.

Natural Occurrence of Alternaria Toxins in the 2015 Wheat from Anhui Province, China

“…Interactions between Alternaria and Fusarium species and consequently their impact on toxin production has been reported by Muller et al [25]. It was found that the increased population of Alternaria on ripening ears of wheat coincided with reduced population of Fusarium species [25,26]. Therefore, the increase of Alternaria toxins in cereals was often accompanied by the decline of Fusarium toxins.…”

“…For example, the species of Alternaria alternata isolated from Argentinean wheat kernels could produce TeA, AOH and AME, but the species of Alternaria infectoria only produce TeA [24]. Interactions between Alternaria and Fusarium species and consequently their impact on toxin production has been reported by Muller et al [25]. It was found that the increased population of Alternaria on ripening ears of wheat coincided with reduced population of Fusarium species [25,26].…”

Spotlight on the Underdogs—An Analysis of Underrepresented Alternaria Mycotoxins Formed Depending on Varying Substrate, Time and Temperature Conditions

“…Interactions of fungi and bacteria with Alternaria could exist more often in competition and in antagonistic processes than in undisturbed coexistence. Few studies dealing with the co-occurrence of Fusarium and fluorescent pseudomonads with Alternaria suggest the implication of mycotoxins as antagonistic substances in these interactions [52,53] Simultaneously, competition processes between different fungal genera affect the production of mycotoxins or increase the metabolization of toxins [54,55]. That means that the production of mycotoxins in natural habitats is influenced by biotic and abiotic factors and could represent various toxin profiles and different concentrations of mycotoxins [56,57].…”

The distribution of mycotoxins in a heterogeneous wheat field in relation to microclimate, fungal and bacterial abundance

“…These results show once again the need of investigating the effects of species interaction on mycotoxins synthesis, confirming what was seen similar to those reported by Müller et al . () where co‐cultivation of fungi in laboratory conditions influence each other metabolic profile.…”