Improved understanding of novel sources of resistance against the light leaf spot pathogen, Pyrenopeziza brassicae

In this work, the endophytic growth phase of the light leaf spot pathogen Pyrenopeziza brassicae in selected lines from a doubled haploid (DH) population of oilseed rape, which is known to segregate for resistance against P. brassicae, was characterised using controlled environment (CE) experiments. Fungal staining techniques and pathogen-specific quantitative polymerase chain reactions (qPCR) were used to observe and quantify the pathogen biomass, respectively. The qPCR results showed that the resistant lines contained little P. brassicae DNA and there seemed to be little to no change in the amount of DNA over time. In contrast, there was a considerable increase in pathogen DNA in susceptible lines from 0 to 24 days post inoculation (dpi). These results were also reflected in observations made by a fungal staining method. In addition, leaf samples of these DH lines, collected at three different times from winter oilseed rape field experiments, were analysed using qPCR. The resistant lines had a considerably smaller amount of P. brassicae DNA in leaf samples collected later in the cropping season than that in susceptible lines.