Alleviation of α-tomatine-induced toxicity to the parasitoid,Hyposoter exiguae,by phytosterols in the diet of the host,Heliothis zea |
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Authors: | Bruce C Campbell Sean S Duffey |
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Affiliation: | (1) Department of Entomology, University of California, 95616 Davis, California;(2) Present address: Western Regional Research Center, USDA, SEA, 800 Buchanan Street, 94710 Berkeley, California |
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Abstract: | The solitary, endoparasitic ichneumonid,Hyposoter exiguae (Viereck) is a parasitoid of the tomato fruitworm,Heliothis zea (Boddie). However, the parasitoid is deleteriously affected by the tomato glycoalkaloid, -tomatine, ingested from hosts (H. zea) fed on artificial diets or semipurified extracts of tomato plants that contained -tomatine. -Tomatine causes prolonged larval development; disruption or prevention of pupal eclosion; deformation of antennal, abdominal, and genital structures; and reduction in adult weight and longevity of the parasitoid. These toxic effects are exacerbated when the dietary dose of -tomatine is increased from 12 mol to 20 mol/g dry wt of diet. However, the toxicity of -tomatine is attenuated in parasitoids reared from hosts fed on artificial diets that contain equimolar or supramolar amounts of 3-OH-sterols admixed with -tomatine. Further, the toxicity of extracts from the foliage of different cultivars of tomatoes toH. exiguae is contingent upon the composite levels of -tomatine and total phytosterol (free and esterified). Cultivars with a low total sterol-tomatine ratio are more toxic toH. exiguae. The possible mode of action of -tomatine toxicity toH. exiguae by disruption of sterol metabolism is discussed. |
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Keywords: | Host-plant resistance -tomatine" target="_blank">gif" alt="agr" align="BASELINE" BORDER="0">-tomatine sterols sterol esters Lycopersicon esculentum Heliothis zea Lepidoptera Noctuidae parasitoids Hyposoter exiguae Hymenoptera Ichneumonidae secondary compounds |
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