Disease resistance in tomato: practical situation

Tomato crops are parasitised by a large and ever increasing number of pathogens. For tomato, the genetic control of pathogens is very used in practice. The sources of resistance occur monogenic and dominant. Their sources are the wild species closely related to the cultivated form. Many open-pollinated varieties presently cultivated posses genetic resistance to three or four pathogens. With the increasing use of F1 hybrids it is possible to use varieties cumulating four to six resistances. During the last years several new resistances were identified and breeders are introducing these in modern varieties cumulating various resistances and particular qualities now required by specific markers, notably fruit long life and good taste. Some interesting resistances are difficult to select. There are the cases with the oligogenic partial resistances also when the resistance tests are difficult to carry out. In some cases using molecular markers can permit the selection. The wild species of Lycopersicon continue to be the hope to control diseases and pests. Nevertheless, modern varieties derived from interspecific crosses can be sources of new resistances sometimes linked to the expected resistances. New hopes appear with the transgenosis, notably to control various viruses. The present practical situation of the genetic resistance is presented for various cultural conditions.