A Virginia Tech research project focused on the dispersal of two wheat pathogens will receive $498,708 over the next three years from the Agriculture and Food Research Initiative, part of the U.S. Department of Agriculture's National Institute of Food and Agriculture program.

Wheat is a staple crop, ranking third among U.S. field crops in planted acreage, production, and gross farm receipts, but yield and grain quality are threatened by diseases, such as rust and Fusarium head blight.

David Schmale, a professor in the Department of Plant Pathology, Physiology, and Weed Science (PPWS) in the College of Agriculture and Life Sciences and an affiliated researcher with the Biological Transport Interdisciplinary Graduate Education Program, will collaborate with Jonathan Boreyko, an assistant professor in the Department of Biomedical Engineering and Mechanics (BEAM) in the College of Engineering (BIOTRANS), and Sunghwan (Sunny) Jung, associate professor in BEAM and an affiliated researcher with the BIOTRANS program.

“Increasing wheat yield in the United States is a top priority for meeting the food security demands of a rising world population. Our research will provide new strategies for minimizing disease spread in wheat, which could help us meet future wheat yield demands,” said Schmale. “Interdisciplinary research is needed to bridge plant pathology and fluid mechanics to study the mechanics of pathogen dispersal.”

Scientists do not yet fully understand mechanistic details of pathogen spread during rain. The team’s preliminary experiments showed that as microscopic dew droplets formed on wheat leaves, they were able to encapsulate rust spores and spontaneously jump several millimeters into the air. Jumping-droplet condensation had not been considered previously as a mechanism for pathogen spread. The specifics of how rain splash physically liberates and disperses spores are also not well understood.

“Our work will transform knowledge of how rain and condensation facilitate the transport of plant pathogens in wheat and other small grains,” said Boreyko. “If jumping droplets indeed prove to be a persistent source of liberation for plant pathogens, the application of a fungicide to a crop could be used to reduce the leaves’ hydrophobicity and suppress this dispersal event.”

Over the next three years, the team will conduct experiments on the leaves and spikes of wheat plants, some with surfaces treated with fungicides. They will also show the synergistic role that rain splash plays in assisting the condensation-driven removal of spores.

The interdisciplinary team of investigators includes Schmale, a plant pathologist; Boreyko, an expert in phase-change phenomena and surface wettability; and, Jung, a fluid mechanist. Integral to their success were former undergraduate students Katrina Somers and Grady Iliff, former graduate student Saurabh Nath, postdoctoral research associate Seungho Kim in BEAM, and laboratory specialist senior Hope Gruszewski in PPWS, who helped coordinate some exciting preliminary experiments that laid the groundwork for the successful grant proposal.

Schmale is an expert in the aerobiology of fungi in the genus Fusarium. He has recently been engaged in research involving the transport and aerosolization of plant pathogens from aquatic environments. Jung has developed technologies with high-speed video to study fluid dynamics and has been working on multiphase dynamics of particles interacting with an interface. Boreyko brings expertise in characterizing phase-change phenomena on surfaces, including the high-speed visualization of condensate on leaves. Boreyko discovered the jumping-droplet phenomenon.

“The dispersal distance of a plant pathogen during precipitation is related to the size and speed of raindrops. Splashing causes the formation of small satellite droplets when a large droplet impacts a surface at a high speed,” said Jung. “By peering into the life history of droplets with high speed video, we hope to understand the dynamics of droplets on crop surfaces with complicated geometries and different surface properties.”

In order to meet cereal crop demand in 2050, world wheat production will need to rise to over 4,000 million metric tons. Yields will need to increase at a much faster pace over the next 30 years. By characterizing the spread of plant pathogens via rain splash and jumping droplet condensation, this research will provide new strategies for minimizing disease spread in wheat that could help producers protect their crops today and help meet future yield demands.

-          Written by Amy Painter

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