Bestämning av förekomst av patogena svampar i vete med PCR-teknik

Today, the quantification of leaf pathogens on wheat mainly relies on a visual inspection and estimation of the percentage of infected leaf area. However, this is both time consuming, requires skilled personnel with experience in plant pathology and may also be misleading if several pathogens are present on the same leaf or if the symptoms are concealed by abiotic factors. More reliable methods suitable for routine diagnosis are necessary to be able to better evaluate and optimise the use of fungicides and different cultivars. In the SLF-project V0648026 "PCR based detection of plant pathogens in wheat", quantitative real-time PCR assays were developed for detection of the three leaf pathogens in winter wheat; Septoria tritici, Drechslera tritici-repentis (DTR) and Stagonospora nodorum. The amount of plant pathogen DNA was determined using relative quantification and a wheat-specific gene was used as reference. With high specificity, high reproducibility and low detection limit, the PCR methods developed enable an objective measurement of fungal infection levels in wheat. The results show a good correlation between visual grading and relative qPCR measurements. Although the visual grading did not report the presence of S. nodorum, this fungi was frequently detected using the qPCR assay. The results also show that qPCR can be used to study the effect of fungicides on the fungal flora with very small variation between replications. In addition, it was shown that qPCR is a useful tool for quantifying the amount of the three wheat pathogens in field trials where different cultivars are evaluated. Pre-symptomatic detection of the pathogens was possible and results show that the PCR-techniques even could be used to evaluate the presence of a few single spores. For the future the results indicates a possibility to improve the evaluation of plant pathogens and plant production systems