Research on breeding for pest resistance has been has been part of the research program of IVT since 1967. Recently research on resistance to insects and mites has been given more attention by a number of Dutch Research Institutes (Sneep & Dieleman, 1973)
Because of an increasing consciousness of the limitations and dangers of the use of insecticides. there is a growing interest in reseach on biological and integrated control. Breeding resistant varieties can substantially contribute of the success of programs of integrated control. If the resistance is of such a level that the economic threshold (Davin & Norgaard, 1973) is not exceeded, the use of resistant varieties can be regarded as the most efficient method of biological control.
The program of breeding tomao resistant to the glasshouse whitefly (Trialeurodes vaporariorum Westw.) was started with screening a collection of accessions of Lycopersicon esculentum Mill. and related species. Low levels of resistance withim L.
During the first few years of our research we extensively studied different methods to test for resistance (Hogenboom et al., 1975) In our opinion non-perference is not a valuable character in monoculture, should it imply that during the orientation and
A screening for resistance of 30 accessions a year was carried out during the summers of 1972, 1973 and 1974. the 85 accessions tested are shown in table I. Beside two standards, 'moneymaker' and 'Allround' , varieties and breeding line of L. esculentum have been chosen because of their resistance to som insect or mite mentioned in literature. the accessions of the wild species have been chosen randomly. These tests were carried out in three replications according to a randomized design. In each replication three young plants were planted in large cages of