New tomatoes have been bred to naturally resist pests and curb disease

A Cornell University researcher has completed a decades-long program to develop new tomato varieties that are naturally pest-resistant and reduce the transmission of viral diseases by insects.

Martha Mochler ChuThe plant breeder and geneticist leading the program recently deposited an initial set of insect-resistant tomato research lines in the USDA Germplasm System and UC Davis Genetics Resource Center, which will be available for anyone to access the plants for research.

This spring, Mutschler-Chu will complete development of a new batch of 20 distinct lines, which will then be made available to any interested seed company, that may breed pest-resistance traits in commercial varieties. It can take up to five years for seed companies to develop new varieties before they start selling new, insect-resistant varieties.

For farmers, these benefits will provide less crop loss and fruit damage, while also eliminating or reducing pesticide use and protecting the environment.

The pest resistance in this tomato was adapted from a wild tomato native to Peru. Solanum pennellii. Andean tomatoes have tiny hairs called trichomes that secrete droplets of sugar compounds, called acylzojars, that repel insects. In this way, the plants safely and naturally deter a variety of insects, preventing them from feeding, eating leaves, transmitting viruses, or laying eggs, the larvae of which may damage plants.

“The new lines combine plants and fruits with better quality and higher levels of acyls, and compound seed companies need to transfer the acylation trait into commercial varieties,” He said Mutchler ChuAnd Professor Emeritus in the School of Integrative Plant Sciences, Department of Plant Breeding and Genetics, part of the School of Agriculture and Life Sciences.

In field and laboratory tests of their primary lines of research, botanists from Cornell University and seven other university partners (North Carolina State University, University of Georgia, University of Clemson, University of Florida, University of California, Davis, University of California, Riverside, and Tennessee Tech) found University) showed that the correct levels and form of sugar acyls controlled western flower thrips, which transmit spotted wilt virus, and sweet potato whiteflies, which transmit yellow leaf curl virus.As a result, far fewer plants were infected with these devastating diseases, and in field experiments, these occurred. infection late in the season.

“To get the best virus control, I suggested that seed companies use a two-tiered approach: create hybrids with both a sugar acyl trait and standard virus resistance genes,” said Mutschler-Chu. If the insects manage to infect the plant with a virus though the sugars, the virus-resistant genes provide additional protection.

“It’s a system that will protect the utility of virus-resistant genes because if there are fewer viruses getting into a plant, the probability that the virus will have a random mutation that generates a strain that overcomes the resistance also decreases,” Mutschler-Chu said. Similarly, because acyl sugars are non-toxic and do not kill insects, there is less selection pressure for the insects themselves to become tolerant, so they adapt more slowly to the repellent.

The new elite strains, which would soon be available to seed companies, contained most of the wild genes from S. pennellii that promote agronomically undesirable traits that are removed from their genomes. Mutschler-Chu retained two critical acyl-sugar genes while removing several other wild genes that caused negative traits such as extra branches, small fruit, and an unfamiliar flavour. While the primary search lines contained about 12% of S. pennellii DNA, the newer strains are down to approximately 2.5% of wild-type DNA.

In broader terms, the work demonstrates in practice a process for incorporating a valuable trait, based on a safe natural compound, controlled by several genes, and effective against multiple viruses and pests, a strategy that could also benefit other crops, Mutschler-Chu said.

While elite lines will be issued non-exclusively to any seed company for breeding traits in their commercial varieties, they will need to apply for a license with the Cornell Technology Licensing Center before they can sell the seeds.

The work was funded by the USDA’s Agricultural and Food Research Initiative.

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