Septoria tritici blotch (STB; Zymoseptoria tritici) is the most important leaf disease of wheat in Northern and Western Europe. The problem of fungicide resistance in Z. tritici populations is challenging future control options. In order to investigate differences in azole performances against STB, 55 field trials were carried out during four seasons (2015-2018). These trials were undertaken in ten different countries across Europe covering a diversity of climatic zones and agricultural practices. During all four seasons, four single azoles (epoxiconazole, prothioconazole, tebuconazole and metconazole) were tested. Increasing variability in the performances of these azoles against STB was observed across Europe. The efficacy of the tested azoles varied considerably across the continent and between countries. The shifts in disease control from these commonly used azoles were confirmed by increasing EC 50 values for epoxiconazole, prothioconazole-desthio and metconazole. The sensitivity towards tebuconazole remained relatively low across the four years. The frequencies of CYP51 mutations varied substantially across Europe, with a clear pattern of significantly decreasing frequencies of D134G, V136A and S524T in the local Z. tritici populations from west to east. In contrast, no major differences were seen for CYP51 mutations V136C, A379 and I381V. The four azoles showed different levels of cross-resistance, which again depended on specific CYP51 mutations. Across the four seasons, the single azoles increased the yields between 9 and 11% on average.
Ergot caused by Claviceps purpurea is a problem for food and feed security in rye due to the occurrence of toxic ergot alkaloids (EAs). For grain elevators and breeders, a quick, easy-to-handle, and cheap screening assay would have a high economic impact. The study was performed to reveal (1) the covariation of ergot severity (= percentage of sclerotia in harvested grain) and the content of 12 EAs determined by high performance liquid chromatography (HPLC) and (2) the covariation between these traits and results of one commercial enzyme linked immunosorbent assays (ELISA). In total, 372 winter rye samples consisting of a diverse set of genotypes, locations from Germany, Austria, and Poland over two years, and three isolates were analyzed. Ergocornine and α-ergocryptine were detected as major EAs. Ergocristinine occurred as a minor component. Claviceps isolates from different countries showed a similar EA spectrum, but different quantities of individual EAs. A moderate, positive covariation between ergot severity and EA content determined by HPLC was observed across two years (r = 0.53, p < 0.01), but large deviation from the regression was detected. ELISA values did neither correlate with the HPLC results nor with ergot severity. In conclusion, a reliable prediction of the EA content based on ergot severity is, at present, not possible.
Clubroot presents a serious threat to cultures of oilseed rape, especially if the share of this plant species in sowing structure is high. This is related to a long-lasting survival of pathogens resting spores in soil. The casual disease agent is Plasmodiophora brassicae Woronin -an obligatory, internal pathogen of Brassicae family which causes the formation of tumors on roots and hypocotyls. Plants with disease symptoms have a confined ability of nutrients' and water uptake and this may cause considerable losses in quantity and quality of potential yield. Monitoring performed in cultivation areas and the information obtained from farmers allowed to confirm a threat of disease occurrence in several voivodeships. At the same time there is a serious danger of the infection spread to other regions of oilseed rape crops.Confining plant infection by clubroot pathogen may be obtained mainly by applying a correct crop rotation, and also by providing resistant varieties for cultivation. In the performed greenhouse experiment, reaction to the infection caused by P. brassicae of chosen winter oilseed rape cultivars was studied. The degree of plant infection was assessed at the growth phase of green bud. It was stated that cv. Mendel revealed significantly the lowest degree of infection, as compared to the other studied cultivars. The other tested varieties were infested in a differentiated degree, however these differences were mostly not confirmed statistically. The infection level was mainly dependent on places of soil derivation.
Rye stem rust caused by Puccinia graminis f. sp. secalis can be found in all European rye growing regions. When the summers are warm and dry, the disease can cause severe yield losses over large areas. To date only little research was done in Europe to trigger resistance breeding. To our knowledge, all varieties currently registered in Germany are susceptible. In this study, three biparental populations of inbred lines and one testcross population developed for mapping resistance were investigated. Over 2 years, 68-70 genotypes per population were tested, each in three locations. Combining the phenotypic data with genotyping results of a custom 10k Infinium iSelect single nucleotide polymorphism (SNP) array, we identified both quantitatively inherited adult plant resistance and monogenic all-stage resistance. A single resistance gene, tentatively named Pgs1, located at the distal end of chromosome 7R, could be identified in two independently developed populations. With high probability, it is closely linked to a nucleotide-binding leucine-rich repeat (NB-LRR) resistance gene homolog. A marker for a competitive allele-specific polymerase chain reaction (KASP) genotyping assay was designed that could explain 73 and 97% of the genetic variance in each of both populations, respectively. Additional investigation of naturally occurring rye leaf rust (caused by Puccinia recondita ROEBERGE) revealed a gene complex on chromosome 7R. The gene Pgs1 and further identified quantitative trait loci (QTL) have high potential to be used for breeding stem rust resistant rye.
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