Effects of plant age and inoculum concentration on light leaf spot disease phenotypes on oilseed rape

Abstract

Light leaf spot is caused by the fungal pathogen Pyrenopeziza brassicae and is the mosteconomically damaging disease of oilseed rape (Brassica napus) in the UK. Current controlrelies on repeated fungicide applications; however, pathogen fungicide-insensitivitydevelopment highlights the need for non-chemical controls like host resistance. A study wasdone to assess light leaf spot disease phenotype on the susceptible B. napus cultivar Charger indifferent treatment conditions; factors studied included plant age and inoculum concentration.Results showed that older plants grown in a controlled-environment cabinet produced the mostvisible symptoms. Plants that received a greater inoculum concentration (105spores/ml) weresignificantly shorter by 5 cm than those inoculated with a smaller inoculum concentration (104spores/ml), suggesting possible correlations between fungal inoculum concentration and plantgrowth. Additionally, > 20 P. brassicae field isolates were collected from leaf samples acrossEngland through single-spore isolation and will be screened for virulence.