In tomatoes, genetic control is based on the exploitation of generally dominant monogenic resistances originating from wild species closely related to the cultivated species. It is one of the model species for the use of monogenic resistance in cultivated varieties.

The two wild species which have so far provided the most resistance genes in cultivated varieties are Solanum pimpinellifolium (ex Lycopersicon pimpinellifolium ) and S. peruvianum (ex L. peruvianum ). By taking the tomato as the female parent, crosses with S. pimpinellifolium are easily made. On the other hand, crosses with S. peruvianum are delicate and require special techniques such as embryo rescue in vitro . It is the same with the species S. chilense (ex L. chilense ), very close to S. peruvianum , and which is at the origin of recent work on resistance to several Begomoviruses . Hybridization of each of these two species with the tomato produces embryos which abort in the seeds well before the fruit ripens. It is therefore necessary to resort to their extraction in the immature state, that is to say 30 to 34 days after hybridization, without waiting for the 55-60 days necessary for the ripening of the fruits of the tomato taken as female. The embryos are cultured in vitro on nutrient medium until plantlets are obtained. Another technique is to pollinate the tomato with a mixture of tomato pollen with pollen from the wild species. This pollination produces many seeds, including some interspecific hybrids. The F1 hybrids obtained are almost self-sterile. To progress towards the cultivated tomato type, breeders must carry out several generations of re-crossing by the tomato. The first crossbreeding requires the use of one of the techniques used to obtain the F1 plants. The following re-crossings are carried out without difficulty.

Another wild species, S. habrochaites (ex L. hirsutum ), brought resistance to the cultivated tomato without great difficulty of hybridization. Its role has become very important as a male parent of F1 hybrids used as rootstocks, both tomato and eggplant. These hybrids are produced by crossing a variety of tomato, which carries dominant genes for resistance to several diseases, particularly of land-based origin (" Ve ", " I ", " I-2 ", " Fr ", " Tm-2 ² " and “ Mi ”) with an ecotype of S. habrochaites , bringing vigor and dominant resistance, one to corky root disease and the other to Didymella lycopersici .

To these resistances should be added resistance to Alternaria alternata f. sp. lycopersici controlled by the “ gene Asc ” present in almost all cultivated varieties, old or recent.

Breeding programs using other resistances from the species mentioned will soon come to an end. Research into exploitable resistance is being carried out in other species Lycopersicon , as well as in distant species belonging to the genus Solanum . Four species belonging to the latter genus ( S. lycopersicoides, S. juglandifolium, S. ochranthum and S. sitiens ), grouped together in the “ juglandifolia ” series, exhibit strong morphological and chromosomal analogies with species of the genus Lycopersicon . Thus, F1 hybrids are easily obtained with S. lycopersicoides , a species of interest for its tolerance to cold and its resistance to Cucumber mosaic virus (CMV), to Clavibacter michiganensis subsp. michiganensis and Botrytis cinerea . However, sterility and incompatibility issues make backcrossing processes difficult.