Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. Tomato varieties used at present for commercial production in Dutch glasshouses have a high density of glandular trichomes on the stem, but a very low density on the leaves, The two-spotted spider mite, Tetranychus urticae Koch, and the predatory mite, Phytoseiulus persimilis AthiasHenriot, usually disperse from leaf to leaf via the stem, thereby incurring high risks of entrapment (and death) in the exudate of the glandular trichomes. These risks have been quantified on the tomato cv. 'Turbo' and an accession of Lycopersicon peruvianum almost free of glandular trichomes. The possible consequences for biological control are discussed and new perspectives for predator release strategies and for plant breeding are considered.

Life history parameters including longevity, developmental time, and reproduction were determined for whiteflies, Trialeurodes vaporariorum (Westwood), kept in clip‐on cages on susceptible parent, Lycopersicon esculentum, resistant parent, L. hirsutum glabratum, and intermediate breeding lines of tomato. Using the Lewontin triangular reproductive function, the intrinsic rate of increase (rm) was calculated for each genotype. This is an elegant tool for detecting resistance, as it incorporates all salient factors of life history. Comparing rm to the other parameters measured, selection criteria were chosen. Developmental time is not a suitable selection criterion as it varies very little even between the most susceptible and the most resistant genotypes. Additionally, developmental time of T. vaporariorum offspring was found to be highly significantly correlated to parental age on all tomato genotypes except L. hirsutum glabratum. Total reproduction, truncated population counts, and longevity appear good criteria for selection. This test, focusing on antibiotic factors, shows large differences between the resistant and susceptible parent genotypes, but much smaller differences between the breeding lines and the susceptible parent. Earlier screenings relying on a variety of tests appear to have maintained antixenotic rather than antibiotic properties in the breeding lines.

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Eighty-five accessions of Lycopersicon esculentum and related species were tested for resistance to the glasshouse whitefly, Trialeurodes vaporariorum WESTW. High levels of resistance were found in L. hirsutum, L. hirsutumglabratum and Solanumpennellii. In other species, too, some resistance was observed. A breeding program is in progress.

INDEX WORDSCucumis sativus, pickling cucumber, parthenocarpy, breeding, environment. SUMMARYParthenocarpic pickling cucumbers have been selected after crossing pickling and slicing cucumbers. On the best lines 90 ~ of the female flowers set fruit (up to 75 fruits per plant within six weeks). At declining daylength productivity decreased, mainly because of a reduced flower initiation and partly by a reduced parthenocarpic potential.The correlation between several selection criteria and the possibilities of preselection of young plants is discussed.