Investigating Wilt with Dr. Tiffany Lowe-Power

Dr. Tiffany Lowe-Power
Dr. Tiffany Lowe-Power

I often wonder what makes my tomatoes wilt. Most of the time it’s because I don’t water them enough (sorry, plants!). But it could also be because they have been infected by a pathogen, causing them to wilt. These pathogens, like the fungus Fusarium and the bacterium Ralstonia solanacearum, are found in the soil and can infiltrate the vascular system of a plant thereby blocking its ability to take in water. This causes the plant to wilt — and die — in a manner that looks almost exactly the same as my thirsty tomato plants. (Check out a video of tomatoes infected with Ralstonia here.) 

I wanted to learn more about pathogenic wilt and reached out to new UC Davis faculty member Dr. Tiffany Lowe-Power, who researches Ralstonia-plant interactions.

This interview has been lightly edited for length and clarity.

Ralstonia life cycle
Illustration by Frank Santoriello. Ralstonia bacteria live in the soil and infiltrate the roots. They move up the vasculature system of the plant, where they replicate and clog the vasculature. Wilting is a symptom of this clog. The bacteria then escape back into the soil through the roots where they can infect more plants.

Sydney Wyatt (SW): Why study Ralstonia wilt specifically when there are so many pathogens that can be responsible for this disease?

Dr. Tiffany Lowe-Power (TLP): Ralstonia wilt is a global problem with large impacts in tropic, sub-tropic and temperate regions [high moisture climates], causing near complete loss of crops. Ralstonia has an incredible ability to infect a broad range of plant species, from crops like tomato, potato and tobacco to ornamentals like geraniums and even trees. Ralstonia infections are also financially devastating: Ralstonia infections caused severe crop loss to the multi-billion dollar tomato industry in the Southeast US. 



SW: This is such a devastating disease. How would one go about treating Ralstonia wilt?

TLP: There are a lot of tricky parts because Ralstonia has such a broad range and survives in the soil, therefore treating just the plant is ineffective. Additionally, some host plants do not show wilting and instead function as reservoirs where Ralstonia replicates and is shed back into the soil [also known as a latent infection]. One could breed for resistance but, for example, breeding for taste, size and yield in tomatoes are more important than breeding for disease resistance for many farmers. However, genetically modifying these tomatoes to add resistance is a possibility. Another option is grafting. Ralstonia enters the plant through the roots, so using a resistant plant’s roots, like eggplant, attached to the rest of a tomato plant could be effective. However, efficient grafting generally requires the two plants to be in the same family (although a new study suggests this may not always be the case) and is a skilled-labor technique, making each plant cost more than twice as much than a regular tomato plant.

Eggplant Tomato Graft
Illustration by Sydney Wyatt. A susceptible tomato plant is grafted onto the roots of a resistant eggplant.

SW: This is clearly an important problem to study. How does your lab study Ralstonia wilt?

TLP: We use the tomato as a model to investigate whether the interactions between Ralstonia and tomato can be generalized to other affected plant species. More specifically, we use genetic techniques to determine which Ralstonia genes are necessary for successful infection in the tomato. We are creating Ralstonia mutants that each lack a single gene. We are competitively growing them against each other in tomato xylem sap [the tomato vascular fluid] and in tomato plants. To determine which mutants lacked pathogenic success, we are counting each mutant by high throughput DNA sequencing. Our goal is to identify the traits that contribute to the survival of the fittest. In the future, we hope to use this same approach in melons, another Ralstonia host, to see if the same genes are important for successful infection across different plants.


SW: You mention you use tomatoes as a model. Given that Ralstonia can infect such a broad range of species, why use the tomato? 

TLP: We love to eat tomatoes, and they are an important cash crop in California, the US and around the world. California produces the majority of “processed tomatoes” in the world; these tomatoes are turned into consumer goods such as canned products, sauces and juice. UC Davis also hosts the Tomato Genetics Resource Center, which provides seeds from diverse cultivated and wild tomatoes to breeders and researchers around the world. This makes tomatoes easy to access for our research. Tomatoes are also easy to work with in research; they are grown from seed and are not finicky plants. We also have a strong network of collaborators who work with tomatoes to understand their susceptibility and resistance to pathogens.  


SW: How can your research contribute to finding a solution to Ralstonia wilt?

TLP: Currently, Ralstonia is screened in plants by detecting its DNA in a sample. By identifying which genes across Ralstonia strains are essential for successful infection, we hope to provide additional information for the identification of new, more aggressive strains of Ralstonia.

Thank you to Dr. Tiffany Lowe-Power for her time. Follow her on Twitter @TLowePower for more content.

Sydney Wyatt is a PhD student at the University of California in Davis.  For more content from the UC Davis science communication group "Science Says", follow us on Twitter @SciSays.

Primary Category