Human oral exposure to aflatoxin B₁(AFB₁) and fumonisin B₁(FB₁) is associated with increased hepatocellular carcinoma. Although evidence suggested interactive AFB₁–FB₁hepatotoxicity, the underlying mechanisms remain mostly unidentified. This work was aimed at evaluating the possible AFB₁–FB₁interplay to induce genetic and cell cycle toxicities in BRL‐3A rat hepatocytes, reactive oxygen species (ROS) involvement, and the AFB₁metabolizing pathways cytochrome P450 (CYP) and arachidonic acid (ArAc) metabolism as ROS contributors. Flow cytometry of stained BRL‐3A hepatocytes was used to study the cell cycle (propidium iodide), ROS intracellular production (DCFH‐DA, HE, DAF‐2 DA), and phospholipase A activity (staining with bis‐BODIPY FL C11‐PC). The CYP1A activity was assessed by the 7‐ethoxyresorufin‐O‐deethylase (EROD) assay. Despite a 48‐h exposure to FB₁(30 μM) not being genotoxic, the AFB₁(20 μM)‐induced micronucleus frequency was overcome by the AFB₁–FB₁mixture (MIX), presumably showing toxin interaction. The mycotoxins blocked G1/S‐phase, but only MIX caused cell death. Overall, the oxidative stress led these alterations as the pretreatment with N‐acetyl‐l‐cysteine reduced such toxic effects. While AFB₁had a major input to the MIX pro‐oxidant activity, with CYP and ArAc metabolism being ROS contributors, these pathways were not involved in the FB₁‐elicited weak oxidative stress. The MIX‐induced micronucleus frequency in N‐acetyl‐l‐cysteine pretreated cells was greater than that caused by AFB₁without antioxidants, suggesting enhanced AFB₁direct genotoxicity probably owing to the higher CYP activity and ArAc metabolism found in MIX. The metabolic pathways modulation by AFB₁–FB₁mixtures could raise its hepatocarcinogenic properties.

Mycoviruses appear to be widespread in Fusarium species worldwide. The aim of this work was to identify mycoviral infections in Fusarium spp., isolated from maize and sorghum grown in Argentina, and to estimate their potential effects on the pathogenicity and toxigenesis of the host fungus towards maize. Mycoviruses were identified in 2 out of 105 isolates analyzed; Fusarium verticillioides strain Sec505 and Fusarium andiyazi strain 162. They were characterized as members of the genus Mitovirus by high-throughput sequencing and sequence analysis. The F. verticillioides mitovirus was a novel mycovirus whereas the F. andiyazi mitovirus was found to be a new strain of a previously identified mitovirus. We have named these mitoviruses, Fusarium verticillioides mitovirus 1 (FvMV1) and Fusarium andiyazi mitovirus 1 strain 162 (FaMV1-162). To our knowledge, FvMV1 is the first mycovirus reported as naturally infecting F. verticillioides, the major causal agent of ear rot and fumonisin producer in corn. Both mitoviruses exhibited 100% vertical transmission rate to microconidia. The Fa162 strain infected with FaMV1-162 did not show phenotypic alterations. In contract, F. verticillioides Sec505 infected with FvMV1 showed increased virulence as well as microconidia and fumonisin-B1 production, compared with two uninfected strains. These results suggest that FvMV1 could have a role in modulating F. verticillioides pathogenicity and toxin production worth further exploring.

Smut fungi, such as Ustilago maydis, have been studied extensively as a model for plant-pathogenic basidiomycetes. However, little attention has been paid to smut diseases of agronomic importance that are caused by species of the genus Thecaphora, probably due to their more localized distribution. Peanut smut incited by Thecaphora frezii has been reported only in South America, and Argentina is the only country where this disease has been noted in commercial peanut production. In this work, important advances in deciphering T. frezii specific biology/pathobiology in relation to potato (T. solani), wheat (U. tritici), and barley (U. nuda) smuts are presented. We summarize the state of knowledge of fungal effectors, functionally characterized to date in U. maydis and most recently in T. thlaspeos, as well as the potential to be present in other Thecaphora species involved in dicot-host interactions like T. frezii-peanut. We also discuss applicability and limitations of currently available methods for identification of smut fungi in different situations and management strategies to reduce their impact on agri-food quality. We conclude by describing some of the challenges in elucidating T. frezii strategies that allow it to infect the host and tolerate or evade plant immune defense mechanisms, and assessing other aspects related to pest control and their implications for human health.