Automated detection of airborne plant pathogen spores

Many important fungal diseases of crops are initiated by airborne spores.  Air sampling can be used to understand the seasonal timing of spore release of plant pathogens, their responses to weather and to identify likely sources of spores.  Currently available DNA-based diagnostic methods applied to air samples are now providing new information about species that previously could not be identified accurately by visual microscopy methods or culturing.  For example a new qPCR method for Sclerotinia sclerotiorum, developed with Carmen Calderon at UNAM, has been used as a research tool and has potential for warning of the presence of airborne inoculum.  However for disease forecasting to be effective for most diseases, air samples need to be analyzed and results disseminated within hours or a few days at most.  Hence, field-based tests are increasingly attractive and new rapid isothermal DNA-based methods, lateral flow immunological kits and automated biosensors are under development.  Air sampling integrated with DNA-based diagnostics can also provide useful information at the sub-species level, such as presence of fungicide resistance or changes in pathotype race structure.  Interpretation of results is often not straight-forward and requires some background knowledge of physics to understand spore-dispersal processes and effects on disease gradients of deposition and dilution in the atmosphere under different atmospheric conditions.  Further work is required to investigate the spatial variability in spore numbers in air at different sites and how changes in numbers of airborne spores at particular heights above or distances away from crops are related to subsequent disease severity in order to optimize inoculum based disease forecasts.

Jon West

 

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