Background

Rust  caused by the fungus Melampsora is the most serious disease in short rotation coppice (SRC) willow plantations for renewable energy. Willows (Salix) are grown as a major SRC crop  for energy because of their yield potential and coppicing ability. In most willows, rust only infects expanded leaves. However, in some willows, such as Salix viminalis and S. caprea, rust also attacks stems and young leaves. When severe, rust defoliates susceptible plantings prematurely and reduces yields by as much as 40%. Severe rust also predisposes plants to infections by secondary pathogens which may lead to death of the plants. 

As the European Union is legally bound to an 8% reduction of greenhouse gas  emission by the year 2010, a large increase of energy from renewable sources is expected. Biomass is one of the most promising sources of renewable energy. It is expected that, in the near future, increasingly large scale energy crop plantations will be established to meet growing demand for energy from renewable sources. The impact of rust is likely to intensify if no control measures are undertaken.

Routine use of fungicides in SRC plantations is not practicable for economic, technical and environmental reasons. The desirable control strategies are integrated utilisation of host resistance and natural processes that limit the damage caused by diseases. These include the selection and breeding for resistance, planting genotype mixtures and biological control of rust using S. filum.  Willows are hugely diverse and, accordingly, have an immense pool of genes that could be used for disease resistance. In planting mixtures, choosing a range of genetically diverse types is considered to enhance the property of mixtures.

Approaches

The programme addresses  population biology and epidemiology of Melampsora, genetics of rust resistance in willows, effects of mixture plantings on rust, potential of Sphaerellopsis filum for biological control.  Partners 01and 02, who have long been working on genetics of Salix/Melampsora interactions,  are be responsible for the work on population genetics of pathogen and genetics of rust resistance.  Partner 03, who has great experience in the study of willow clone mixtures, plays a leading role in studies of mixtures and disease epidemiology. Partner 01 is also responsible for the work on S.  filum.  Partner 04, who specialises forest pathology and ecology, leads the studies of pathogen variation and identification of sources of resistance.

The work is carried out using both biological assay methods and modern molecular techniques.  In vitro pathogenicity/resistance tests, morphological examination,  alternate-host inoculation and field disease assessments are the main techniques to be used  to characterise the  identity and pathogenicity of rust, resistance in willows and efficacy of S. filum.  AFLP is the main means of analysing population structure of rust and S.  filum.  Ribosomal DNA sequence  information will be used to characterise species/forms of Melampsora. As the project investigates natural populations of the pathogen and the mycoparasite and seeks for practicable ways of controlling rust, much work is conducted using field trials. Mixture trials, willow collections and commercial willow trials in participating countries are being used for major field experimentation.

Contact Information

01582 763133 Ext 2635

(+44)01582 760981

Rothamsted Research, Harpenden, Herts, AL5 2JQ, UK

General Information:  mingpei@bbsrc.ac.uk