Abstract
A combination of staining, light microscopy and SYBR green- and dual-labelled fluorescent probe-based qPCR chemistries with species- and gene-specific primers was employed to evaluate fluctuations in the aerial biomass of Leptosphaeria maculans spores captured by volumetric spore trappings in Poznan, Poland (2006, 2008) and Harpenden, UK (2002, 2006). Arising from these surveys, DNA samples extracted from Burkard spore-trap tapes were screened for fluctuation patterns in the frequencies of AvrLm1 and AvrLm6, the most prominent of the 15 genes that code for avirulence effectors in this Dothideomycete cause of the destructive phoma stem canker disease of oilseed rape worldwide. In Poznan, very low frequencies of AvrLm1 allele were found in the autumn of both 2006 and 2008, reflecting significantly increased cultivation of rape seed with Rlm1-based resistance. In contrast, at least six folds-higher frequencies of AvrLm6, which were also confirmed by end-point PCR bioassays on phoma-infected leaves from the same region of Poland, were obtained during both years. In the UK, however, relatively higher AvrLm1 allele titres were found in L. maculans spores captured in air samples from the autumn of 2002 on the experimental fields of Rothamsted Research, Harpenden, that were historically sown to genetically heterogeneous B. napus cultivars. In the 2006 screen these levels had plummeted, to a 1:4 ratio, in favour of frequencies of the AvrLm6 allele. Patterns of fluctuations in erg11 (CYP51) fragments coding for sterol 14α-demethylase suggest October as the month with the most viable wind-dispersed L. maculans propagules of each season of the screens.
Highlights
Various techniques for spore capture are increasingly being used in supporting decisions on the protection of agricultural crops against important pathogens causing great yield losses
A combination of staining, light microscopy and SYBR green- and dual-labelled fluorescent probe-based qPCR chemistries with species- and gene-specific primers was employed to evaluate fluctuations in the aerial biomass of Leptosphaeria maculans spores captured by volumetric spore trappings in Poznan, Poland (2006, 2008) and Harpenden, UK (2002, 2006)
In Europe, the biggest monitoring system based on spore counts is the System for Forecasting Disease Epidemics (SPEC; Jedryczka et al 2004, 2012) which was designed in Poland for monitoring the aerial dynamics of ascospore concentrations of the pathogen Leptosphaeria maculans, the cause of the phoma stem canker disease of oilseed rape
Summary
Various techniques for spore capture are increasingly being used in supporting decisions on the protection of agricultural crops against important pathogens causing great yield losses. In Europe, the biggest monitoring system based on spore counts is the System for Forecasting Disease Epidemics (SPEC; Jedryczka et al 2004, 2012) which was designed in Poland for monitoring the aerial dynamics of ascospore concentrations of the pathogen Leptosphaeria maculans, the cause of the phoma stem canker disease of oilseed rape. This damaging disease is prevalent on brassicas worldwide (Fitt et al 2006), except for China and India, where. The genome of this dothideomycete fungus was sequenced and the annotations of fungal avirulence genes have been released publicly (Rouxel et al 2011)
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