The Problem

The fungal pathogens Rhynchosporium secalis and Ramularia collo-cygni are important pathogens of barley in the UK. Leaf scald (R. secalis) is classified as the most damaging disease of barley and is a major reason for fungicide use.  Little is known about the relative importance of the different inoculum transmission mechanisms for both of these pathogens although it is considered that seed-borne infection may play an important role in the spread of the disease after which rain splash dispersal of spores spreads the fungus to higher parts of the plant.

Project Aims

To determine the mechanisms whereby Rhynchosporium and Ramularia infect seed and subsequent spread to leaves using genetically characterised, tagged pathogen isolates. Subsequently to utilise this knowledge to improve resistance breeding and fungicide control strategies.

Approach

Genetically characterise a selection of Rhynchosporium and Ramularia isolates and transform them with fluorescent markers. Carry out detailed microscopy investigations on seeds, seedlings and adult plants infected with marked isolates to determine where the pathogens are and how they are transmitted between plant growth stages. Determine whether contrasting resistance sources and developmental stages affect the infection and transmission processes identified microscopically. Characterise the response of the pathogens microscopically to chemical seed treatments. Determine the role of seed-borne infection on the spread of fungal pathogens, and initial fungal density upon disease severity.

Benefits to the industry

This project will enable breeders to obtain knowledge of the mechanisms whereby different resistance sources affect pathogen attack and subsequent symptom expression. This will help target resistance breeding strategies. Knowledge of the key developmental triggers which affect symptom expression, together with diagnostics, will help optimise fungicide control programmes. A reduction in fungicide applications would provide an additional environmental benefit through decreased agrochemical inputs into the agro-ecosystem and reduced fuel use, as well as less impact upon the soil system.