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.”
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.”
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