A new Fusarium mycotoxin glucoside, fusarenon X-glucoside (FUXGlc), is reported for the first time in wheat grain that was artificially infected with Fusarium fungi. This new glucoside was identified using LC Orbitrap high-resolution mass spectrometry (LC–Orbitrap MS) analysis on the basis of accurate mass measurement of characteristic ions and MS/MS fragmentation patterns. Although the absolute structure of FUXGlc was not clarified by LC–MS, 3-OH glucosylation seems to be the most probable structure based on the fragment profile and considering that deoxynivalenol-3-glucoside (DON3Glc) was reported as the predominant glucosylated derivative of the structurally similar mycotoxin, deoxynivalenol (DON). Another mycotoxin glucoside, nivalenol-glucoside (NIVGlc) was also found in the same grain sample. According to the semi-quantification by LC–Orbitrap MS, more than 15% of FUX and NIV were estimated to be converted into respective glucosides. The existence of these masked mycotoxins should be taken into account in risk assessment, since they could be transformed back to the corresponding mycotoxins under certain conditions; for example, through various food processing operations or in the digestive tract of mammals after ingestion.

Fusarium graminearum is responsible for Fusarium head blight (FHB), which is a destructive disease of wheat that makes its quality unsuitable for end use. To understand the temporal molecular response against this pathogen, microarray gene expression analysis was carried out at two time points on three wheat genotypes, the spikes of which were infected by Fusarium graminearum. The greatest number of genes was upregulated in Nobeokabouzu-komugi followed by Sumai 3, whereas the minimum expression in Gamenya was at three days after inoculation (dai). In Nobeokabouzu-komugi, high expression of detoxification genes, such as multidrug-resistant protein, multidrug resistance-associated protein, UDP-glycosyltransferase and ABC transporters, in addition to systemic defense-related genes, were identified at the early stage of infection. This early response of the highly-resistant genotype implies a different resistance response from the other resistant genotype, Sumai 3, primarily containing local defense-related genes, such as cell wall defense genes. In Gamenya, the expression of all three functional groups was minimal. The differences in these molecular responses with respect to the time points confirmed the variation in the genotypes. For the first time, we report the nature of gene expression in the FHB-highly resistant cv. Nobeokabouzu-komugi during the disease establishment stage and the possible underlying molecular response.

The existence of di-glucosylated derivative of T-2 toxin in plant (corn powder) was confirmed for the first time in addition to that of HT-2 toxin. These masked mycotoxins (mycotoxin glucosides) were identified as T-2 toxin-di-glucoside (T2GlcGlc) and HT-2 toxin-di-glucoside (HT2GlcGlc) based on accurate mass measurements of characteristic ions and fragmentation patterns using high-resolution liquid chromatography-Orbitrap mass spectrometric (LC-Orbitrap MS) analysis. Although the absolute structure of T2GlcGlc was not clarified, two glucose molecules were suggested to be conjugated at 3-OH position in tandem when considering the structure of T-2 toxin. On the other hand, the specification of the structure seems to be more complicated in the case of HT2GlcGlc, since HT-2 toxin has two possible positions (at 3-OH and 4-OH) to be glusocylated. In addition, 15-monoacetoxyscirpenol-glucoside (MASGlc) was also detected in the identical sample.

Masked mycotoxins (mycotoxin glucosides) derived from type A trichothecenes were detected in commercially available corn powder reference material. These new glucosides were identified as neosolaniol-glucoside (NESGlc) and diacetoxyscirpenol-glucoside (DASGlc) on the basis of accurate mass measurements of characteristic ions and fragmentation patterns using high-resolution liquid chromatography–Orbitrap mass spectrometric (LC-Orbitrap MS) analysis. Although the absolute structure was not clarified, 3-OH glucosylation appeared to be the most probable when considering the structures of neosolaniol and diacetoxyscirpenol and the fragmentation profiles of these masked mycotoxins. Concomitant detection of deoxynivalenol-3-glucoside, the most well-known masked mycotoxin derived from the type B trichothecene, deoxynivalenol, in the identical material further supports this probability.

Fusarium fujikuroi, a member of the Fusarium fujikuroi species complex, stands out as a rice bakanae disease pathogen with a high production of gibberellic acid. Not all, but some F. fujikuroi strains are known to produce a carcinogenic mycotoxin fumonisin. Fumonisin biosynthesis is dependent on the FUM cluster composed of 16 FUM genes. The FUM cluster was detected not only from a fumonisin producing strain, but also from a fumonisin nonproducing strain that does not produce a detectable level of fumonisin. Genetic mapping indicated the causative mutation(s) of fumonisin nonproduction is present in the FUM cluster of the fumonisin nonproducing strain. Comparative analyses of FUM genes between the fumonisin producing and the nonproducing strains and gene complementation indicated that causative mutation of fumonisin nonproduction is not a single occurrence and the mutations are distributed in FUM21 and FUM7. Our research revealed a natural variation in the FUM cluster involving fumonisin production difference in F. fujikuroi.

Fusarium head blight (FHB) causes significant grain loss and contamination of grains with harmful mycotoxins, especially deoxynivalenol (DON). Fusarium resistance and DON accumulation have been extensively investigated in various cultivars; however, the level of DON-3-O-glucoside (D3G) has not been as carefully studied. In this study, we measured accumulated DON and D3G levels in CIMMYT wheat elite germplasm using an analytical method validated in-house. Co-occurring nivalenol (NIV) and ergostrerol (ERG) were also analyzed. LC-MS/MS and LC-UV analyses were applied to the 50 CIMMYT elite wheat lines. D3G showed rather high correlation with DON (r = 0.82), while FHB symptoms showed slight correlation with DON and D3G (r = 0.36 and 0.32, respectively). D3G/DON ratio varied widely from 8.1 to 37.7%, and the ratio was not related with FHB resistance in this dataset.