Texas researcher receives Foundation for Food and Agriculture Research Award

Award presented for Early-Career Innovation in Plant Pathology

Media contact: Blair Fannin, 979-845-2259, [email protected]

Writer: Kathleen Phillips

Contact: Dr. Kranthi Mandadi, 956-969-5634, [email protected]

WESLACO — Scientists are closing in fast on a problem threatening to destroy the world’s orange juice and potato supplies as well as many other foods with a possible solution coming from the root of the issue — hairy roots, to be exact.

“The biggest challenge has been that the pathogens that cause citrus greening and potato zebra chip disease belong to a group of similar pathogens ‘fastidious’ because scientists have not been able to culture them in the lab. That poses a big problem to study them and to come up with timely solutions,” said Dr. Kranthi Mandadi, assistant professor in the department of plant pathology and microbiology at the Texas A&M AgriLife Research and Extension Center-Weslaco. “Fastidious pathogens are crazy. They can infect almost all plants.”

Scientists have devoted careers attempting to find ways to culture and study fastidious plant pathogens in the lab using specialized media and expensive apparatus to little success, he said. The lack of a simple and broadly applicable laboratory method means researchers must resort to traditional methods that require a lot of time and money.

“For example, we had identified new resistance genes with a potential for combating citrus greening disease, but I thought, ‘How can we test them? It takes forever to test,’” Mandadi said, noting that his collaborator, Dr. Erik Mirkov, professor of plant pathology and microbiology at AgriLife Research-Weslaco, had already spent two years testing two genes in citrus.

“The current way to test disease resistance genes is to make a transgenic plant expressing a gene that might resist a pathogen, then grow the transgenic plant until it is old enough to be challenged by a pathogen, then observe whether the plant is affected or not,” Mandadi said. “It takes a year or more.”

Not only does it take time, but producing enough plants to verify tests is costly and labor intensive, he said.

“I wondered how long it would take to test 25 genes. That is when I came upon the concept of using hairy roots as an alternative approach to propagate fastidious pathogens, as well as test many of these genes faster,” Mandadi said.

Hairy roots are plant tissues created by briefly treating a plant with a naturally occurring soil bacterium that causes plant tissues to grow lots of hair-like roots. They have long been used by biologists to study plant genetics, as well as to produce high-value compounds.

Mandadi set out to explore using a hairy root system to propagate fastidious pathogens from already infected plants, as well as to determine if the system can be used to screen potential treatments.

“This is the first time anybody has tested hairy roots to culture fastidious pathogens,” Mandadi said. “Also, this will provide a simpler way to test disease resistance genes and antimicrobial molecules effective against the fastidious pathogens.”

His lab worked for about two years to develop a proof-of-concept for this “microbial hairy root bioassay” to propagate fastidious pathogens and test different antimicrobials that may work against the fastidious pathogen.   

His novel approach has been boosted by an approximately $600,000 New Innovator award from the Foundation for Food and Agriculture Research, 50 percent of which was matched by Southern Garden Citrus of Florida to test treatments on citrus greening.

“The Foundation for Food and Agriculture Research is pleased to support Mandadi’s research as part of our work to catalyze innovation and foster a strong scientific workforce for the future,” said Sally Rockey, executive director of FFAR. “I look forward to seeing the impact of the New Innovator in Food and Agriculture Research award not only on Mandadi’s career, but also on advancing agriculture.”

According to foundation, the new innovator awards are intended “to support and promote the future generation of exceptionally talented and creative new faculty who are conducting critical research and establishing research programs that will lead to expanded availability of food and facilitate the global practice of sustainable agriculture as the world’s population grows to more than 9 billion people by the year 2050.”

Citrus greening and potato zebra chip will be the foremost diseases tackled by the research, but Mandadi said his work with hairy roots lends itself to most other plant diseases that can cause sharp declines in yields and take an equal bite out of what’s available to feed the world’s growing population.

This simple yet powerful microbial hairy root technology, he said, can be scaled-up and potentially used to perform large-scale screening of therapeutics and/or active ingredients effective against diverse fastidious pathogens.

“Currently, to screen for efficacy of any chemicals against citrus greening, they are either sprayed or injected into a mature infected citrus tree, grown in soil, to find out what will kill the pathogen inside the trees,” he said. “Imagine how many trees are needed to spray a chemical in a test. As an alternative approach, we can switch to microbial hairy root bioassays in vitro that will allow screening a large number of molecules or chemicals rather easily. This also gives us an opportunity to save a lot of time and come up with solutions faster.”

Mandadi said this will also have a huge impact on the plant pathology community, given that it can be used to utilize the same technology for other crop maladies such as those caused by fastidious viruses, viroid’s, phytoplasmas, mycoplasmas and fungi.

Hairy roots can be produced from most, if not all, plants.

After the citrus and potato trials, Mandadi, with the support of Southern Garden Citrus, plans to expand the platform to evaluate many other fastidious pathogens that adversely affect food crops such as on grapes and olives.

The second annual set of New Innovator awards bring the total FFAR investment in the program to more than $5 million. New Innovators are also required to demonstrate a commitment to mentoring and supporting the foundation’s  interest in inspiring future generations of agricultural and food scientists.

Learn more about the 2017 New Innovators and their research directions: http://foundationfar.org/new-innovator/.