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Howard Judelson

Professor of Plant Pathology and Microbiology
Howard Judelson
Environment-Friendly Food Security for the World
Late blight diseases, which first appeared in the mid-19th century as the cause of the Irish Famine, continue to wreak havoc for potato and tomato growers worldwide. In 2009, for example, late blight devastated tomato crops in both commercial operations and home gardens on the East Coast to the tune of $290 million. Using gene transfer tools they pioneered and other genetic, bioinformatic and biochemical approaches, Judelson's lab studies the pathogen's life cycle, seeking improved strategies for battling such plant diseases.

Areas of Expertise

Select Honors and Distinctions

  • Ruth Allen Award, American Phytopathological Society (2004)

Latest Research


Q: What are the goals of your research?
We are trying to identify genes and proteins important to the growth, development and pathology of Phytophthora infestans and its relatives, which include hundreds of other important pathogens. What we learn can be used to help defeat pathogens in the field through environmentally safe chemical or plant-based solutions, and to develop diagnostic tools that growers can use to help manage disease. Plant pathogens cause hundreds of billions of dollars of losses per year to crops, including those that we grow for food, fiber, or fuel. In an affluent country like the United States, we mostly battle pathogens using chemical agents, but they are expensive, may have adverse environmental effects, and are not always effective. In a less-affluent part of the world, crop disease might lead to famine.

Q: Tell us about your most recent USDA grant and how it addresses sustainability.
Most conventional and organic growers control late blight by applying chemical fungicides. Chemical control is costly, may have adverse environmental effects and is often performed inefficiently. Information about where the pathogen is present is not always available, and disease forecasting models do not consider trait variation between different strains of the pathogen. For example, strains vary in their sensitivity to different fungicides and the optimal temperature for infection, but forecasting tools treat all strains the same. Our grant aims to reduce overall fungicide use, which will both reduce on-farm costs and be better for the environment. We will provide growers with better tools to predict when the disease threatens their crop, information about pathogen traits that will help them choose the best treatment regime and plants that are more resistant to the disease.

Q: What related research fosters sustainability?
Many researchers study the mechanisms that Phytophthora uses to form its spores, and how the spores germinate and infect the plant host. Spores are essential for the disease cycle, since plant-to-plant dissemination of the disease usually relies on wind-borne spores. One reason why Phytophthora infestans is such a successful pathogen is that it generates enormous numbers of sophisticated spores. They release cells that swim towards plants and then develop specialized structures that tunnel through the thick outer surface of a leaf. There is also a second type of spore, called the oospore, which is extremely durable and can survive in soil for many years. By identifying genes and proteins involved in the biology of the spores, we hope to identify new, environmentally benign strategies for disease control.

Q: Your research has worldwide implications. Where have your research projects taken you?
Potato is an enormously important crop throughout the world, and late blight occurs on every continent except Antarctica. We therefore collaborate with scientists around the world, mostly based in Europe and Asia. Most of our work is done here in the laboratory in Riverside, but we are also involved in field trials in India and Bangladesh, and over the past year have visited scientists in the United Kingdom, China and all over the United States. Scientists from other countries frequently visit us to learn new methods for studying Phytophthora; this year, we provided training to visitors from Colombia, England, Ireland, Scotland, and Spain.

Q: Why does your latest USDA grant involve people from so many different disciplines?
There is probably no single "magic bullet" to stop late blight, so we have to test many different approaches. Our group therefore includes plant pathologists, molecular biologists, sociologists, plant breeders, computer programmers, economists, meteorologists, bioinformaticians, extension scientists, and others, which includes both scientists that work mainly in the lab and in the field. For example, at the same time that our lab-based programs are developing diagnostic assays and computational tools to forecast disease, we have sociologists and communication specialists investigating how to bring those technologies to the grower using smartphones, social media, and traditional approaches.

Q: Where did the inspiration come from for your research?
Ever look through a microscope at pond water? Or the surface of a leaf? The world is full of tiny microbes, such as fungi, bacteria, and single-cell protists. They influence so much of our lives in both destructive and beneficial ways. I became especially excited about species like Phytophthora when I saw diagrams of their life cycles in a textbook when I was in college. How could these simple organisms be so complex, making all sorts of different cell types? I have spent the last 30 years trying to answer that question.

Q: What doesn’t the public know or understand about this kind of research?
First, I don't think that people realize how much of a threat pathogens pose to food production. We are lucky to have an inexpensive and ample food supply, but a devastating disease can always be just around the corner, which might lead to higher prices, the disappearance of some foods from store shelves or hunger. We can't afford to be complacent. Second, I don't think that people realize how slow or unpredictable progress in research can be. It can take decades for a scientist to make an important discovery, and predicting what type of research leads to outcomes useful to society is very difficult. As individual scientists and as society, we just have to keep trying.

Q: What does “Living the Promise” mean to you?
There are two parts to my answer. The first is that every day we learn more about our natural world, and there is the potential to use that information to better our lives. The second part is that as a member of a state university, who obtains research grants from federal agencies, I have a responsibility to contribute to the public good through my research and by training future scientists. I also must help students learn to think more scientifically so that they can make logical, evidence-based decisions in their lives and also to be more curious about the world around us.
Howard Judelson"The world must double its food production by 2050. We can't afford to ignore plant diseases and need sustainable solutions. That means producing enough food crops without damaging our health or the environment, and enabling farmers to make a profit. When growers go out of business, that is bad for everyone."

—Howard Judelson
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