Fusarium head blight (FHB) is a fungal disease causing substantial yield and quality losses in barley. Genetic variation in deoxynivalenol (DON) content and and important yield traits in response to FHB were studied in 44 spring barley cultivars for two years following artificial inoculation with Fusarium culmorum under field conditions. The analysis of variance revealed that the largest effect on DON content and simultaneously on the reduction of thousand grain weight and grain weight per spike were due to the environmental conditions of the year, while the visual disease symptoms depended on the cultivars to a larger extent. All these traits were significantly interrelated. The most resistant cultivars Murasski mochi, Nordic, Krasnodarskij 35, Krasnodarskij 95, Nordus, and Usurijskij 8, together with the resistant check Chevron, showed the lowest DON content, the lowest expression of disease symptoms and the lowest reduction of TGW and GWS. However, most spring barley cultivars registered in the Czech Republic in recent years expressed susceptibility or medium resistance and were considerably affected by the disease. This increases the importance of breeding barley for resistance to FHB.

A real-time polymerase chain reaction (PCR) assay was developed for the specific detection of Fusarium culmorum in infected seeds. Primers and TaqMan minor groove binder probe were derived from the sequences of a F. culmorum specific PCR product. The specificity of the assay was confirmed by test in seven Fusarium species and 21 non-Fusarium fungal species. With serial dilutions of purified genomic DNA from F. culmorum isolate B as the template, the detection limit of the assay was found to be 0.9 pg of fungal genomic DNA per reaction. A significant correlation (r 2 average ¼ 0.982) and collinearity was found between DNA concentration and Ct (cycle threshold) values of real-time PCR assay with serial diluted DNAs extracted from three seed samples with different deoxynivalenol (DON) content. Eight barley and nine wheat varieties infected by F. culmorum isolate B were evaluated in 1 (barley samples) and in 4 years (wheat samples). The results of real-time PCR analysis and enzyme-linked immunosorbent assay testing for DON content were compared and a significant correlation was found for barley samples (r 2 ¼ 0.935). Concerning wheat we found rather complicated relationship between Ct values and DON contents influenced by environmental conditions of field trials. The real-time PCR assay was found to be highly specific and sensitive. It could be used in phytopathological studies and praxis.

This study investigated the distribution and characteristics of the Barley yellow dwarf virus (BYDV) species BYDV-PAS, which was recently separated from BYDV-PAV, the most commonly studied BYDV species. Throughout 3 years of experimental monitoring of BYDV incidence, PAS was the most frequently occurring species infecting cereals and grasses in the Czech Republic. Furthermore, Rhopalosiphum maidis and Metopolophium dirhodum were recorded as BYDV-PAS vectors, even though M. dirhodum does not usually transmit BYDV-PAV. In field experiments with barley and wheat, where virus accumulation, symptoms and effect on the yield were tested, BYDV-PAV was more severe than PAS. Infection with the BYDV-PAV isolate resulted in greater expression of symptoms and also in a greater reduction in plant height and grain weight per spike than BYDV-PAS. In a sensitive cultivar of barley (Graciosa), the amount of viral RNA of BYDV-PAV was also significantly higher than that of BYDV-PAS. In a tolerant line (Wbon-123), however, no such differences were found. In conclusion, although BYDV-PAS seems to be dominant in the Czech Republic, BYDV-PAV has the potential to cause more significant crop losses in barley and wheat.

The review focuses on recent progress in the breeding of small grain cereals (barley, wheat, oats) for resistance to the barley yellow dwarf virus (BYDV). First, the symptomatology of barley yellow dwarf (BYD) disease is briefly described and the genome of BYDV, its serotypes and mechanisms of its replication and translation in host plants are characterized. Great attention is paid to the description of resistance genes and sources of BYDV resistance that are currently used in some breeding programmes of barley, wheat and oats. In barley, the introduction of the Ryd2 gene into high-yielding cultivars is still desirable. An example of recent success reached in a European programme aimed at a pyramiding of resistance genes is the registration of the Italian feeding barley cultivar Doria, carrying resistance genes Ryd2, rym4 and Rdg1. The release of this cultivar resulted from the cooperation between EICR, Fiorenzuola d’Arda and CRI in Prague-Ruzyně in the field of virus resistance. Finally, some experiments employing transgenic techniques in the construction of resistant plants are mentioned. In conclusion, the advantages and disadvantages of classical breeding methods using crossing and transgenic techniques are compared and newly arising approaches are discussed.

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