Monitoring of airborne downy mildew sporangia in Southern California
Citation
Ayala, H., Van Der Heyden, H., and Putman, A. 2023. Monitoring of airborne downy mildew sporangia in Southern California. (Poster) Plant Health 2023, Denver, Colorado.
Plain language summary
Downy mildew of lettuce (caused by Bremia lactucae) and onion (Peronospora destructor) are important diseases with the potential to cause significant economic loss. In interior production areas of California, USA, the incidence of these downy mildew diseases can vary season-to-season and are often difficult to predict. Moreover, the dynamics of airborne inoculum in these geographic areas have not yet been characterized. The objective of this research was to determine airborne concentrations of sporangia of these two pathogens in Imperial County, CA. One Burkard 7-day volumetric spore sampler and one Spornado Sampler were placed at two locations and collected one and three times per week, respectively, from late January to May 2022. The Melinex tape from the Burkard trap was sectioned into 24-hour days and split in half for either DNA extraction or identification using compound microscopy. The Spornado cassette filters were processed for DNA extraction only. P. destructor DNA was quantified using a qPCR assay. B. lactucae sporangia were detected microscopically in the Burkard samples from the end of January to the end of May in an average of 83% of samples. P. destructor sporangia were only found in an average of 6% of samples by microscopy. The peak of detection of both these pathogens occurred from mid-April to May. qPCR results will be presented. Information on the airborne inoculum dynamics of these pathogens would be valuable for the future development of warning systems based on pathogen presence.
Abstract
Downy mildew of lettuce (caused by Bremia lactucae) and onion (Peronospora destructor) are important diseases with the potential to cause significant economic loss. In interior production areas of California, USA, the incidence of these downy mildew diseases can vary season-to-season and are often difficult to predict. Moreover, the dynamics of airborne inoculum in these geographic areas have not yet been characterized. The objective of this research was to determine airborne concentrations of sporangia of these two pathogens in Imperial County, CA. One Burkard 7-day volumetric spore sampler and one Spornado Sampler were placed at two locations and collected one and three times per week, respectively, from late January to May 2022. The Melinex tape from the Burkard trap was sectioned into 24-hour days and split in half for either DNA extraction or identification using compound microscopy. The Spornado cassette filters were processed for DNA extraction only. P. destructor DNA was quantified using a qPCR assay. B. lactucae sporangia were detected microscopically in the Burkard samples from the end of January to the end of May in an average of 83% of samples. P. destructor sporangia were only found in an average of 6% of samples by microscopy. The peak of detection of both these pathogens occurred from mid-April to May. qPCR results will be presented. Information on the airborne inoculum dynamics of these pathogens would be valuable for the future development of warning systems based on pathogen presence.