Courtesy of Jason Koski/Cornell University

After exploration of more than a decade, a new line of tomatoes was bred under Prof. Mutschler-Chu's program.

January 26, 2023

Prof. Emeritus Martha Mutschler-Chu Develops Pest, Disease-Resistant Tomatoes

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Prof. Emeritus Martha Mutschler-Chu just finished decades of research on tomato plants, with her development of 20 lines of pest and disease-resistant breeds slated to conclude this spring. Focused on novel traits in wild tomatoes, Mutschler-Chu was looking for ways to lower the use of chemicals in agriculture while still maintaining crop health. 

“Biotic stresses cause a lot of loss of either yield or crop quality,” Mutschler-Chu said. “The general solution for diseases or insects is to spray the plants with fungicides, bactericides or insecticides. A number of these that have been used in the recent decades are not safe and have implications for the people working on the farms, the environment and consumers.” 

Mutschler-Chu led the research program in collaboration with other researchers from Cornell, North Carolina State University, University of Georgia, Clemson University, University of Florida, University of California, Davis, University of California, Riverside and Tennessee Tech University. Mustchler-Chu emphasized the importance of working with scientists across different disciplines. 

“I could not have done all the work myself, [for example], I am not an entomologist. I know enough entomology to work with an entomologist, but I am not one … and at the same time, they are not breeder geneticists either,” Mutschler-Chu said. “A lot of science today really has to be done in collaboration because we are looking at questions and systems that require a breadth of different information, different knowledge and different techniques.”

To begin their research on pest-resistance, the scientists honed in on a wild tomato from Peru, specifically studying trichomes — little hairs all over the ground part of the plant.

“These trichomes are like little factories. The last cell at the top of the trichome produces these acylsugars and exudes them as little droplets, which are profoundly repulsive to insects,” Mutschler-Chu said. 

Mutschler-Chu saw this sugar’s potential to largely eliminate the need for insecticides — chemicals used to control insects — as it irritates insects when they land on the plant, leading pests to leave the plant on their own. After discovering acylsugars’ potential to deter insects, Mutschler-Chu and her team delved into genetics research. 

“So first step, figure out it was acylsugars. Second step, start the genetics process and breeding process to figure out, how do we transfer this trait? How complex is that inheritance of one gene? Is it a bunch of genes?” Mutschler-Chu said. 

After about 10 years of research, Mutschler-Chu and her colleagues developed an initial line of tomatoes. Although this line did not represent a final product, the team recognized it as an important first step in their project.

Mutschler-Chu noted that this project, focused on insect resistance, was the longest part of her research, calling it “the most complicated trade we worked with.” When Mutschler-Chu and the Cornell team began working, the genetic tools necessary to complete the project had not even been fully developed yet. 

“The molecular biologists were creating all these wonderful new tools, and turns out, I needed some of these tools to finalize the project,” Mutschler-Chu said. “But it was okay, because we still made a lot of progress — it was only the final steps that needed the new tools.”

Not only did the acylsugar discovery help to eliminate insects, but it also lowered disease transmission. Mutschler-Chu explained that plant viruses are typically carried by insects, so diverting insects secondarily minimized disease transmission.

The tomatoes are Mutschler-Chu’s last stop in her academic journey — she will retire after the complete launch of the new seed line. The newest line stands at approximately 2.5 percent wild DNA. Mutschler-Chu noted that her work could not have been done without the help of colleagues and mentors.

“Everybody learns from everyone else, science is a cumulative process,” Mutschler-Chu said. “Each new generation stands on the shoulders of the past generation.”