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Winter wheat samples infected by eyespot were collected during the years 2015–2017. In total 143 Oculimacula spp. isolates were obtained and determined by PCR. Oculimacula yallundae isolates prevailed (122) over Oculimacula acuformis isolates (12) and 9 mixed isolates of both species. O. acuformis predominated only on one locality. The reaction of 104 Oculimacula spp. isolates to ten different fungicides was evaluated in laboratory tests on Petri dishes. The highest efficacy showed the combination of epoxiconazole + fluxapyroxad + pyraclostrobin and the lowest efficacy was evaluated after application of prothioconazole + trifloxystrobin. The decrease of efficacy of fungicide no. 6 (prothioconazole + trifloxystrobin) has been observed since 2015. The sensitivity of 114 Oculimacula spp. isolates to prochloraz has been tested. More than half of the isolates (58%) showed low to medium resistance. One isolate of O. yallundae from the year 2017 showed high resistance to prochloraz (ED50 ranged 1.7 μg ∙ ml–1). The rest of the isolates (42%) were sensitive to prochloraz.
The current study was focused on fungi colonizing the stem bases of wheat. Particularly, fungal species with significant harmful effect on wheat were studied. The dynamics of the stem base colonization by these fungi over the growing season were observed, and the association between individual pathogenic fungi was also evaluated. In addition, the fungal leaf sheaths penetration, which can cause physical disturbance, was assessed. The asymptomatic presence of fungal DNA in wheat tissue was confirmed. Microdochium nivale was found on the stem bases most frequently. Other fungi, such as Oculimacula spp., Rhizoctonia cerealis and Fusarium spp., were presented considerable less frequently. The statistical significant association was confirmed only between M. nivale var. nivale and M. nivale var. majus . Out of these, M. nivale tended to decrease in summer season, the frequency of occurrence of Oculimacula spp. and R. cerealis increased at later growth stages. Along with this, these species infected only plants previously colonized by M. nivale . Asignificant relationship between visual symptoms and presence of M. nivale DNA in the host tissue was confirmed.
The fungus Ramularia collo-cygni is increasingly important as the causal agent of Ramularia leaf spot (RLS). The work aimed to identify gene resources suitable for developing new breeding lines of spring barley with improved resistance. We tested 144 spring barley cultivars at 3 locations in the Czech Republic over 3 years (2009–2011). Only minor and statistically insignificant differences were observed between the individual cultivars in reaction to RLS. No cultivars were observed to have resistance to Ramularia collo-cygni, but significant influence of location and year on the intensity of RLS infection in barley was observed.
Fusarium head blight caused by a complex of Fusarium species is widespread across the world and ranks among the most serious diseases in cereals. Long-term field experiments were set up to evaluate the effects of preceding crop and soil management methods on Fusarium mycotoxin (DON, deoxynivalenol) contamination of winter wheat and spring barley grain. Winter wheat and spring barley were cultivated at two locations in the Czech Republic (A: Ivanovice na Hané during 2002–2014, and B: Žabčice during 2007–2014) with preceding crops (A) alfalfa, maize, and pea; and (B) alfalfa (only for wheat), sugar beet (only for barley), and maize. Different soil management methods also were used: (A) 22 cm tillage, 15 cm tillage, 10 cm chisel, and direct drilling; and (B) 22 cm tillage, 10 cm chisel, and direct drilling. Mycotoxin content in harvested grain was analysed using ELISA. At both locations in the experiments with both wheat and barley, year had a significant effect on mycotoxin content in grain. Preceding crop was another significant factor in wheat experiments at both locations, with DON content in grain higher with maize as the preceding crop than in the cases of other preceding crops. Soil management method had a significant effect only on mycotoxin content in wheat grain grown at Žabčice, and the highest DON content was determined in the chisel variant, in which case a large amount of harvest residue remained on the soil surface or was only partially incorporated.