Ask most people what a wild tomato is, and they picture one plant. There are actually sixteen.
Each one grows wild across a narrow stretch of western South America and the Galapagos Islands. Most gardeners have never heard of any of them by name.
That is a shame. These plants are the reason a modern tomato can survive diseases that would have wiped out earlier varieties.
This guide covers what a wild tomato species actually is. It also covers where they grow, and which ones quietly reshaped the tomato in your garden.
The short version
Sixteen wild species make up the tomato’s closest relatives. That count comes from the University of California, Davis Tomato Genetics Resource Center.
All of them grow naturally in a narrow band from Ecuador down through Peru and Chile. That range includes the Galapagos Islands.
Solanum pimpinellifolium is the closest wild relative to the cultivated tomato. It has small, red, pea sized fruit, and it crosses easily with garden varieties.
Other wild species look nothing like a tomato at first glance. Some have fuzzy leaves, some have green or yellow fruit, and some grow in near desert conditions.
Breeders have pulled specific disease resistance genes from at least seven different wild species. Many resistant varieties sold today carry genes that trace straight back to a wild plant most gardeners never see.
What actually counts as a wild tomato
A wild tomato is any of the sixteen Solanum species closely related to the cultivated tomato. None of them were ever domesticated themselves.
The UC Davis Tomato Genetics Resource Center maintains the standard taxonomic key used to sort them. Species get grouped partly by leaf shape and partly by fruit color.
Red fruited species sit closest to garden tomatoes. That group includes Solanum pimpinellifolium and the semi domesticated Solanum lycopersicum var. cerasiforme.
Green and whitish fruited species form a separate group entirely. Solanum peruvianum, Solanum chilense, and Solanum habrochaites belong to that group, along with several others whose fruit never turns red at all.
Two species are Galapagos Islands endemics. Solanum cheesmaniae and Solanum galapagense grow nowhere else in the wild.
They stayed isolated on the islands long enough to develop their own distinct traits. None of these plants look much like a supermarket tomato.
Fruit size ranges from a small currant down to something closer to a large pea. Several species have fuzzy, almost silver colored leaves instead of the smooth green most gardeners expect.
The genes hiding in your garden tomato
Wild species are not just a botanical curiosity. A peer reviewed review of tomato breeding traced specific disease resistance genes in modern varieties back to individual wild species.
Solanum pimpinellifolium alone has contributed resistance genes against fusarium wilt, late blight, early blight, bacterial wilt, bacterial spot, leaf mold, and tomato spotted wilt virus. Its close relationship to the cultivated tomato makes it the easiest wild species to cross with garden varieties.
Solanum habrochaites, the fuzzy leaved species, contributed different resistance genes. Its list includes late blight, leaf mold, tomato yellow leaf curl virus, and powdery mildew.
Solanum peruvianum is the source of the Sw-5 gene. That gene is the main defense against tomato spotted wilt virus in resistant varieties sold today.
The same species also contributed root knot nematode and verticillium wilt resistance. Solanum chilense contributed additional tomato yellow leaf curl virus resistance genes, and it grows in some of the driest, highest conditions of any wild tomato species.
Solanum pennellii is suited to marginal, stressed habitats. It passed along fusarium wilt resistance and genes that help repel a wide range of insects.
Even the Galapagos endemic Solanum galapagense contributed something specific. Breeders have used it as a source of whitefly resistance genes.
What growers actually find when they try wild tomatoes
Wild tomato seed does circulate among home growers. Most of what circulates is small hybrid swarms and named selections rather than the pure wild species themselves.
Results on gardening forums are decidedly mixed. One grower on a fruit growing forum described Matt’s Wild Cherry, a semi wild selection, producing a steady stream of small, sweet fruit with almost no maintenance.
Another grower singled out a specific wild accession called LA2533 as unusually flavorful for a pea sized tomato. That same accession also carries late blight resistance genes.
Not every report was positive. A different grower described a wild hybrid swarm producing fruit that was, in their words, not particularly memorable, with some ripe fruit turning soft and mealy.
That mixed picture matches what the resistance gene research suggests. Wild species were never selected for flavor or size.
They were shaped by survival in tough conditions instead. That is exactly why they carry traits modern breeding still needs.
For more on how those traits show up in the varieties gardeners actually plant, see this site’s guide to disease resistant tomatoes.
Frequently asked questions
How many wild tomato species are there?
Sixteen, according to the taxonomic key maintained by the University of California, Davis Tomato Genetics Resource Center. They range from close relatives of the cultivated tomato to distantly related species with green or whitish fruit.
What is the closest wild relative to the garden tomato?
Solanum pimpinellifolium. It has small, red, pea sized fruit, crosses easily with cultivated varieties, and has contributed more documented disease resistance genes to modern breeding than any other wild species.
Where do wild tomatoes grow naturally?
Along a narrow band of western South America stretching from Ecuador through Peru into Chile, plus the Galapagos Islands. Two species, Solanum cheesmaniae and Solanum galapagense, grow only on the Galapagos Islands and nowhere else in the wild.
Do wild tomatoes taste good?
Results vary widely. Some wild derived selections produce sweet, flavorful small fruit, while others produce fruit gardeners describe as bland or mealy, since wild species were never bred for flavor in the first place.
Are any modern tomato varieties resistant to disease because of wild species?
Yes, many are. The Sw-5 gene protecting against tomato spotted wilt virus traces back to Solanum peruvianum, and resistance genes for late blight, leaf mold, and several other diseases trace back to Solanum pimpinellifolium and Solanum habrochaites.
Bottom line: a wild tomato is not one plant but sixteen distinct species, most of them growing wild across a narrow strip of South America and the Galapagos Islands. Solanum pimpinellifolium remains the closest and most useful relative for breeders, but at least seven wild species have each donated specific disease resistance genes now found in tomatoes gardeners grow every year. The next resistant variety label on a seed packet likely owes something to a plant most people will never see growing in the wild.
Sources
Genetic Resources journal: The Role of Tomato Wild Relatives in Breeding Disease Free Varieties