Development of detection systems for the sporangia of Peronospora destructor

Abstract

A monoclonal antibody that recognises components of the wall of sporangia of Peronospora destructor was raised. Tests using spores of higher fungi and other species of mildew demonstrated the specificity of the monoclonal. The antibody was used to develop lateral flow devices for sporangia of P. destructor. A competitive lateral flow format was developed which could detect onion downy mildew sporangia. Five-microliter gold anti-mouse IgM solution pre-mixed with 10 μl of P. destructor monoclonal antibody (EMA 242) proved the optimal concentration for detection of sporangia of P. destructor when applied to sample pads of lateral flow devices. Limits of approximately 500 sporangia of P. destructor could be detected by the absence of a test line on the lateral flow device within test samples. Using a scanning densitometer improved the sensitivity of detection. Further development and validation of the test is required if it is to be used for risk assessments of onion downy mildew in the field.

Quantitative studies on downy mildew (Peronospora destructor Berk. Casp.) affecting onion seed production in southern Uruguay

“…During the production of onion bulbs, the presence of dwarf plants with curved leaves and fully covered by Dm sporulation, also observed in Uruguay, allows speculation about systemic Dm infections from the beginning of the season (Virányi 1981;Maeso 2005). Recent and ongoing development of immunoassaybased detection of P. destructor (Kennedy and Wakeham 2008) and molecular tests as developed for other Peronosporales (Scott et al 2004;Tsay et al 2006) will contribute to elucidate the role of seed transmission in the dynamics of this disease.…”

Diagnostic tests and their application in the management of soil- and water-borne oomycete pathogen species

“…Early detection of incoming inoculum can be effectively achieved using spore sampling network devices (Skelsey et al , ), and such measurements have been used to improve the precision of fungicide decision support systems for potato blight – guiding the timing, and also giving early and precise indications as to the efficacy, of disease management decisions (Fall et al , ). More rapid and precise molecular techniques have allowed similar observations in potato blight and other disease systems (Skottrup et al , ; Kennedy & Wakeham ; Wakeham & Kennedy, ), readily providing sufficient time for the application of targeted protectant control measures (Wakeham, ; Thiessen et al , ; West & Kimber, ).…”

“…Air samples are only tested when environmental conditions are suitable for Mycosphaerella brassicicola infection (Wakeham & Kennedy, ). In‐field lateral flow tests have also been developed to monitor bio‐aerosols for the oomycete pathogens P. destructor (onion downy mildew) and Albugo candida (white blister on Brassica oleracea ) (Kennedy & Wakeham, ; Wakeham, ). On the other hand, the specificity and sensitivity that can be achieved with molecular DNA‐based methods is impressive and real advances have been made towards the deployment of DNA‐based systems to the field and in the reduction of analysis cost (Thiessen et al , ).…”

Innovations in air sampling to detect plant pathogens

“…This makes the system relatively inexpensive and has reduced fungicide application to crops that would have occurred if farmers relied only on weather-based infection conditions to indicate disease risk. Lateral flow device tests applied to cyclone air samples have also been developed to provide warnings of Peronospora destructor (onion downy mildew) (Kennedy & Wakeham, 2008 ).…”