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Cornell hosts global plant disease experts, shares latest research

Magdalen Lindeberg
Magdalen Lindeberg discusses the use of genome sequencing to identify pathogenic bacteria that affect tomatoes during a presentation at the American Phytopathological Society (APS) Northeastern Division conference Oct. 20 in Ithaca. (Matt Hayes / College of Agriculture and Life Sciences) 

During the Irish potato famine, humanity began to realize that our survival depends upon understanding plant diseases, as much as the diseases that sicken us directly. Today, with rapid population growth and a changing climate that threatens to spread diseases far beyond their current ranges, the need for research in plant pathology has perhaps never been more urgent.

 “The time frame for solving global plant health crises is pretty frightening,” said Gary Bergstrom, professor and chair of the Plant Pathology and Plant-Microbe Biology Section of the School of Integrative Plant Science (SIPS). “But we have some important new technologies and a new generation of scientists that are being prepared to address these challenges.”

During the annual meeting of the American Phytopathological Society (APS) Northeastern Division, hosted last week in Ithaca, researchers discussed using genome sequencing to better understand plant pathogens, as well as how growers can optimize timing of fungicide and fertilizer applications to more effectively manage diseases on their farms, and much in between.

Cornell shone at the conference: in addition to hosting the meeting for the first time in 20 years, two of the four distinguished symposium speakers were Cornellians, and both student presentation award winners are Cornell graduate students.

Meg McGrath, associate professor of Plant Pathology and Plant-Microbe Biology (PPPMB), organized the meeting, and is now president of the Northeastern Division of the APS.

“Our symposium focused on the role of genome sequencing in practical disease management,” McGrath said. “We now have the entire genomes of some plants and pathogens. With this information, plant-pathogen interactions can be studied to a greater depth leading to understanding what makes a pathogen a pathogen, and identifying new ways to obtain resistance in a plant. We can use new molecular tools to more precisely develop resistant varieties without introducing foreign genes, in contrast with how transgenic plants have been developed.”

Magdalen Lindeberg, senior research associate in PPPMB, is working on exactly that idea with tomatoes, and the bacterial pathogen Pseudomonas syringae. Lindeberg and colleagues in PPPMB and at the Boyce Thompson Institute are using genome sequencing to identify the factors that pathogens use to suppress the plant immune system and sicken healthy plants. Once the most critical factors are understood, over 200 varieties of wild and heirloom tomatoes will be tested for resistance genes that can be transferred into commercial varieties.

“One of the benefits of SIPS, which is made up of five formerly independent departments, is that it encompasses activities ranging from the most basic, fundamental plant research to applications that are making a difference for growers in New York and beyond,” she said. “Collaborations among scientists within the School can make a huge difference for the progress of research.”

Stacy DeBlasio, a postdoctoral scientist in Professor Michelle Cilia’s lab, is studying the protein interactions between the potato leafroll virus and green peach aphids, which spread the disease to healthy potato plants.

Aphids can’t spread the virus simply by touch; they must ingest the virus, circulate it internally, then spread it through saliva. DeBlasio is trying to see if she can disrupt that cycle. One promising idea is virus-induced gene silencing, in which researchers utilize small RNAs produced by genetically modified plant viruses, to disrupt the expression of proteins within the aphid that are involved in virus movement through the insect, thus blocking transmission of the virus to a new plant. A similar technique is already being tested to combat citrus greening, another insect-transmitted bacteria that’s devastating citrus plants worldwide.

Doctoral students Megan Hall and Laura Morales were co-recipients of the Graduate Student Presentation award at the conference.

APS award
Laura Morales, center, receives Graduate Student Presentation Award at the APS conference in Ithaca. (Meg McGrath / College of Agriculture and Life Sciences)

Morales, studying under Professor Rebecca Nelson in the Section of Plant Breeding and Genetics, presented on ways to develop better methods for detecting maize grain contaminated with a fungus dangerous to human and animal health.

Hall, who works with Professor Wayne Wilcox in PPPMB, explained her work on sour rot, a poorly understood disease that appears in grapes just before harvest, with devastating impacts for growers.

Hall found her way to plant pathology after working in a vineyard in Oregon and realizing that “the thing that governed the season more than anything else was disease.”

She’s discovered that sour rot is a disease complex involving yeast, bacteria, and fruit flies. Fighting it requires an anti-microbial spray, along with an insecticide. Neither alone has much impact.

“I have worked with growers year after year,” Hall said. “And now they finally have tools to deal with this disease.”

Krisy Gashler is a freelance writer in the College of Agriculture and Life Sciences