PROCESSING TOMATO BREEDING IN THE 90'S: A UNION OF TRADITIONAL AND MOLECULAR TECHNIQUES

The genetic base of the cultivated tomato species is very narrow. Fortunately, very high levels of genetic variability are available in the easily accessible wild species of Lycopersicon. Despite considarable use of the wild species, utheir great range and diversity mean that they remain a largely untapped genetic resource. Molecular-assisted breeding promises to make introgression of characters from wild species faster and surer. The low frequency of isozyme variation restricts their use in traditional breeding, however, Restriction Fragment Linked Polymorphisms (RFLPs) and Random Amplified Polymorphic DNAs (RAPDs) are much more common and show great potential for molecular- assisted breeding. Using RFLPs and RAPDs to tag genes and to confirm elimination of unwanted allen DNA are powerful tools to speed introgression of desired traits from wild species. Recombinant DNA technology also has significant potential to expand the germplasm available to tomato breeders. This technology promises to solve recalcitrant problems that have been difficult to solve using traditional breeding. Among the traits that are frequently mentioned as solvable with transgenic techniques are; insect resistance, virus resistance, stress tolerance, herbicide resistance, higher fruit solids, improved fruil color. etc. The successful tomato breeder of the future will be the one who is the best able to combine three components of modern tomato breeding: 1) the art of plant breeding: 2) identifying and introgressing genes from wild species: and 3) accessing and utilizing genes from other species using rDNA techniques. Tomato breeding in the fulure will be more challenging — and more exciting — then it has ever been before.