Arthropod resistance and 2,3-dihydrofarnesoic acid in hybrids of Lycopersicon esculentum x L. hirsutum (Tetranychus urticae, Myzus persicae)

In order to evaluate the potential for genetically transferring insect repellence from a wild plant species to a cultivated species, interspecific hybrids of Lycopersicon esculentum × L. hirsutum (LA1363), were evaluated for chemical aspects of their leaflet extracts and screened for resistance to two-spotted spider mite, Tetrapychus urticae. Compared to LA1363, in F1 hybrids 2,3-dihydrofamesoic acid was present, but at low concentration. 2,3-Dihydrofarnesoic acid was not present in F2 and BC1 families except in an F2 family that arose from sib mating of F1 plants. Novel compounds, compounds not present in either parent, occurred at low concentrations in F1, F2 and BC1 generations.; No plant in the F1 generation had a chemical composition phenotype, based on leaflet area, similar to that of LA1363. However, TLC and GC chromatograms of leaflet extracts from F2 and BC1 generations allowed identification of a unique F2 plant, SIB15. SIB15 possessed abundant 2,3-dihydrofarnesoic acid as well as some novel compounds.; The resistance to mites in the F1 generation was intermediate to the two parents. 2,3-dihydrofarnesoic acid could not explain the resistance of the F1 population.; A resistance mechanism other than repellence occurred in the F1 population. This mechanism was characterized by plants having complete coverage with mites but with no feeding damage. A similar mechanism was observed in F2 and BC1 populations.; Two F2 plants were identified as repellent in a thumbtack bioassay—SIB15 and SIB4. Leaflet extracts from these two plants were repellent when tested with the diving board bioassay. Similar to the repellent parent, the acid fractions of these two F2 plants contained 2,3-dihydrofarnesoic acid as a main component and were more repellent than the neutral fractions. The trichome type and density phenotypes of LA1363 were recovered on SIB15 which had a high density of type IV trichomes. SIB4 had lower type IV trichome density.; A leaf disk bioassay for evaluating the activity of compounds on aphids was developed. This bioassay was easy to set up and monitor. Leaflet extracts of LA1363, SIB15 and SIB4 repelled aphids, Myzus persicae, from settling. The active compounds were mainly present in the acid fraction.