DEVELOPMENT OF RAPID DIAGNOSTICS FOR MONITORING LEAF DISEASES OF VEGETABLE BRASSICAS AND ALLIUMS

Endemic plant pathogens pose an increasingly significant threat to UK agriculture, horticulture, amenity planting and natural ecosystems. There is a cost associated with their control through crop-protective chemistry and resistant varieties. Significant losses are caused to crop yields from a variety of existing fungi and oomycetes. Fungal pathogens occurring on vegetable brassica crops can be difficult to control. At present, designating disease risk, as a method for applying control measures involves the use of mathematical models which summarize the effect of environment on key life cycle stages of target pathogens. Approaches based on the direct measurement of fungal spores in the air have been developed based on immunological techniques. These tests have also been used to determine risk.

Detecting airborne spores of fungal plant pathogens is a useful approach in crop protection because at this stage the spores have not infected the crop. Determining the relationship between exposure to inoculum of plant pathogens and subsequent symptom development is complex in the field, as the dose threshold above which symptoms are observed varies spatially. Rapid diagnostic devices for in-field detection of air-borne conidia of a range of brassica pathogens and onion downy mildew have been successfully developed and tested by Warwickshire College Group in association with the UK horticultural industry.

The technology can also be linked to meteorological parameters such as air mass movement for predicting variation over wider geographic areas. Development of these detection technologies would improve our understanding of the interaction between R gene and Avr gene combinations which would enable predictive deployment of cultivars as a method which does not rely on pesticide sprays for control of airborne plant pathogens.