University of Georgia

Size matters


The gene variants that control a tomato’s size have been found by UGA geneticists, who published their findings in the open-access journal PLOS Genetics.

Esther van der Knaap has spent much of her career working to understand the genetic shifts that occurred between ancestral, wild tomatoes and the modern, cultivated varieties that we eat today. Now, van der Knaap has helped to pinpoint a gene that regulates the size of the tomato’s individual cells, which in turn helps to regulate the size of the overall fruit.

“Knowledge of the gene will open up avenues of research into how fruit size can be increased further without negatively impacting other important qualities such as disease resistance and flavor,” said van der Knaap, a professor in UGA’s department of horticulture and Institute of Plant Breeding, Genetics and Genomics.

Van der Knaap and her colleagues investigated a gene they named Cell Size Regulator, or CSR, that increases fruit weight by enlarging the individual cells in the fleshy part of the tomato. Unlike wild tomatoes, domesticated varieties carry a mutation in the CSR gene that affects the way tomato cells develop before they ripen and fall off the plant.

The variation originated in the cherry tomato but now appears in all large cultivated tomato varieties.

This brief appeared in the fall 2017 issue of Research Magazine. The original press release is available at