Effect of Fusarium culmorum Tri Gene Transcription on Deoxynivalenol and D3G Levels in Two Different Barley Cultivars

Abstract

Fusarium culmorum is a phytopathogenic fungus causing Fusarium head blight (FHB), which negatively affects cereals by producing mycotoxins, such as deoxynivalenol (DON). In this work, two barley cultivars, Chevron and Pedant, with different degrees of resistance to FHB were inoculated with F. culmorum. The transcription levels of the Fusarium Tri genes and barley UDP‐glycosyltransferase genes were investigated. The amounts of pathogen, DON and the detoxification product deoxynivalenol‐3‐O‐glucoside (D3G) were monitored. The greatest amounts of pathogen were detected at 21 days postinoculation (dpi) and were much lower in cv. Chevron than in cv. Pedant. No differences in the total DON conversion to D3G were observed between the cultivars. Ubiquitin‐conjugating enzyme (UBC) was identified and then used as a reference gene to monitor transcription of the Fusarium Tri genes in infected barley. Transcription of the F. culmorum Tri5, Tri4, Tri6 and Tri10 genes differed between the two cultivars. In the susceptible cultivar (Pedant), transcription of the Tri genes gradually increased from 1 dpi. In the more resistant Chevron, transcription of the Tri genes dramatically increased after 14 dpi and reached a maximum at 21 dpi. This very high but delayed transcription of Tri genes did not, however, result in a large accumulation of the mycotoxin DON. The difference between the cultivars in the transcription of barley defence genes (HvUGT13248 [GT2] and HvUGT5876 [GT1]) for UDP‐glycosyltransferases reflects the barley samples’ levels of infection. The difference in resistance to F. culmorum infection in the two cultivars is most likely not due to differences in DON detoxification, but may be due to activity against the pathogen and delayed transcription of the pathogen's Tri genes.

Changes in the content of various Fusarium mycotoxins forms in germinating winter wheat and spring barley kernels

“…In germination process, when seeds try to survive, transformed D3G can increase more, even to 3:1 ratio (Figure 1a, wheat). D3G levels depend on ability of cereal genotype transform DON to D3G, as confirmed Faltusová et al (2015) from comparison of susceptible and more resistant cultivars. Plant breeders consider this ability as a key trait for resistance of genotypes to Fusarium in breeding (Shin et al 2012).…”

Fusarium culmorum Tri genes and barley Hvugt13248 gene transcription in infected barley cultivars

“…These factors such as weather conditions around flowering, pathogen virulence and agricultural practices (crop rotation, soil cultivation, fertiliser, chemical treatment) were summarised by Edwards (2004). This work and our previous study examining two barley cultivars differing in Fusarium resistance (Faltusová et al 2015) suggest some ability of the host to delay transcription of the pathogen's Tri genes. We expect that further deeper examination of the Tri gene regulation transcription could help to find possibilities of decreasing mycotoxin production by Fusarium.…”

“…Transcription of Fusarium Tri genes Tri4 and Tri5 was greater in the most infected cultivars Nordus and Diplom, and this observation is consistent with the high DON content in these cultivars. In the case of regulatory genes, transcription differed between 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 (Faltusová et al 2015) and with that of Kumaraswamy et al (2011), who concluded in agreement with Boutigny et al (2009) that the D3G/DON ratio may not correctly identify the mechanisms of resistance inasmuch as the DON reduction can be due both to DON conversion to D3G and its reduced synthesis. Resistance based on a modification of trichothecenes is important in terms of the plant's own resistance.…”

“…Faltusová et al 2015). As summarised byMerhej et al (2012), many studies were aimed at the regulation of trichothecene biosynthesis in F. graminearum.…”