P-4: 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
most economically damaging disease of oilseed rape (Brassica napus) in the UK. Current
control relies on repeated fungicide applications; however, pathogen fungicide-insensitivity
development highlights the need for non-chemical controls like host resistance. A study was
done to assess the light leaf spot disease phenotype on the susceptible B. napus cultivar Charger in different treatment conditions; factors studied included plant age and inoculum
concentration. Results showed that older plants grown in a controlled-environment cabinet
produced the most visible symptoms. Plants that received higher inoculum concentration (105 spores/ml) were significantly shorter by 5 cm than those inoculated with lower inoculum
concentration (104 spores/ml), suggesting possible correlations between fungal inoculum
concentration and plant growth. Additionally, > 25 P. brassicae field isolates were collected
from leaf samples across England through single-spore isolation and will be screened for
virulence.