Will tomatoes be the next big commercial crop for vertical farms?

University of California-Riverside researchers Martha Orozco-Cárdenas (above) and Robert Jinkerson are using CRISPR gene-editing technology to develop short tomato plants that have the potential to be grown in vertical farms and on the International Space Station. Photos courtesy of Robert Jinkerson, Univ. of Calif.-Riverside Photos courtesy of Robert Jinkerson, Univ. of Calif.-Riverside

Researchers at University of California-Riverside are using CRISPR technology to develop miniature tomato plants for production in vertical farms and on the International Space Station.

What crops come to mind when you think of vertical farm production? Leafy greens, microgreens and herbs are likely the most common answer. How about tomatoes?

University of California researchers Robert Jinkerson and Martha Orozco-Cárdenas are using CRISPR-Cas9 gene-editing technology to develop short tomato plants that have the potential to be grown in vertical farms and on the International Space Station. Orozco-Cárdenas initially used CRISPR technology to reduce the size of normal tomato plants, including the number of leaves and stems, without significantly reducing the size and yield of the fruit.

“The tomatoes originally were under investigation by my collaborator Dr. Orozco-Cárdenas, who is director of the UC-Riverside Plant Transformation Research Center,” Jinkerson said. “I was touring her research facility and saw tomato plants that were fruiting in vitro. The plants were incredibly small. I thought these tomatoes would have a lot of different applications, particularly for NASA. We also determined that the tomatoes could be well suited for vertical farming. It started out as a basic science project investigating gene function and we expanded it to look toward other applications where genes could be mutated to control plant architecture for vertical farming and for space flight applications.

“For the first iteration, Dr. Orozco-Cárdenas took an existing dwarf tomato plant variety and used CRISPR gene editing to further shrink the plants. Currently we are working on using the CRISPR technology to stack more mutations on top of the original variety. We are also performing gene editing in a commercial indeterminate variety to determine if we can alter the plant architecture and size so that they would be suitable for vertical farm production.”

Limits to plant size

Jinkerson said the CRISPR gene-editing technology can be used to create mutations that affect the inflorescence, number of flowers and branching architecture. Initially plant size was the trait the two researchers were interested in changing, but Jinkerson said he has expanded the studies to include the impact on fruit size and yields.

“We are looking primarily at how we can grow the plants to the smallest size and still produce the highest fruit yield to maximize the harvest index,” Jinkerson said. “The harvest index is the amount and weight of the fruit vs. the weight of the total plant biomass, including the fruit. If there was 100 percent fruit then the harvest index would be 100 percent. But because plants need leaves, stems and roots, the harvest index can’t be 100 percent.

“There is a point where the plant becomes so small that there are not enough leaves to perform photosynthesis and the plant won’t be able to support the fruit that it is trying to produce. This is something we have to keep in mind as we try to balance the plant size and how much vegetative biomass is needed to produce the fruit. Currently we are investigating this relationship. We think we are starting to hit the lower limit of size where we cannot make the plants much smaller without negatively affecting the fruit yields.”

Overcoming vertical farm limitations

Jinkerson’s tomato research is being funded by a $450,000 New Innovator grant from the Foundation for Food & Agriculture Research. Even though Jinkerson’s background is in engineering and algae, he saw the potential that vertical farming could have on future food supplies.

“Most commercial crops are grown outdoors and there really are not any restrictions on size,” he said. “For vertical farming there is a lot of work that needs to be done to customize crops for this new production environment. For instance, the plants can only be a certain size and should have a quick production time to reach harvest. They should also be very efficient with the way they utilize artificial light for photosynthesis because electricity for lighting is one of the largest operating costs.”

Part of the FFAR grant is for Jinkerson to work with commercial growers to determine how the short tomatoes that are developed work in their production systems.

“We are interested in finding commercial growers who are operating vertical farms or a commercial partner who can help trial and evaluate the lines that we have already produced and future lines we will be developing,” he said. “Another aspect of the research grant is to take other tomato varieties and try to optimize their architecture for vertical farms in order to have a greater variety of fruit that can be grown in these systems.”

Although Jinkerson does not have a vertical farm set up at the university, he is trialing the plants in a greenhouse and a controlled environment room equipped with fluorescent lights.

“The grow room with fluorescent lighting that we are using is not like a high tech vertical farm equipped with LEDs,” he said. “The plants have been grown with a photon flux of a few hundred μmol m⁻² s⁻¹ PAR at a 16 hour photoperiod. The temperature and humidity have been maintained at normal room conditions. We haven’t tried to optimize environmental conditions for plant growth yet. We haven’t pushed the plants under any extreme conditions, but these are future areas of research we are interested in exploring.”

Jinkerson and his students are also collecting data related to the amount of light that is needed for the plants to flower and fruit under artificial light.

“We have fruit yield data,” he said. “We have done a lot of calculations on fruit yield per volume. This is an important metric for vertical farms. With our data we can estimate what type of yields we could expect with the plants. Depending on the vertical spacing distance, the yield per volume for the plants we have developed could be anywhere between 1.5 to three times higher compared to greenhouse yields.”

Future crops for vertical farms, space travel

While Jinkerson’s current research is focused on tomatoes he said there is the potential to apply the gene-editing technology being developed to other vertical farm crops.

“We are going to start with other Solanaceae crops, including peppers, eggplant and potatoes,” he said. “We think that many of the findings we have identified with tomato will be able to translate to these other crops because they are closely related to tomato.”

Part of the research on the tomatoes is being funded by NASA and will be used to conduct a seed-to-seed experiment in space.

“The goal is to grow tomato plants on the International Space Station to fruit and have the astronauts harvest the seed,” Jinkerson said. “The astronauts will then take the seed and grow them for the next crop to have them fruit again. This process is essential in order to have a sustainable crop system for food production. This has never been demonstrated before with tomatoes on the space station.”

The astronauts are currently producing leafy greens on the space station.

“There is very limited physical space on the space station so trying to maximize the harvest index is essential,” Jinkerson said. “This is a very good analog for vertical farms on Earth. With leafy greens the astronauts are able to eat everything but the roots, making these plants perfect for space travel. However, NASA is interested in growing other crops in space. There is an experiment planned for peppers coming up in the next year and our experiment with tomatoes in the next two to three years. Just like vertical farm growers on Earth, astronauts will be trying to produce different types of crops in space.”

For more: Robert Jinkerson, University of California-Riverside, Chemical and Environmental Engineering Department; robert.jinkerson@ucr.edu; http://jinkersonlab.engr.ucr.edu/.

This article is property of Urban Ag News and was written by David Kuack, a freelance technical writer in Fort Worth, Texas.