The genetic basis of host range inHeliothis virescens: larval survival and growth |
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Authors: | A L Sheck and F Gould |
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Institution: | (1) Department of Entomology, North Carolina State University, 27642 Raleigh, NC, USA |
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Abstract: | Larval feeding was assayed in a generalist caterpillar (Heliothis virescens (F.)), a specialist caterpillar (Heliothis subflexa (Gn.)), their F1 hybrids and a backcross withH. s. to gain a preliminary understanding of the genetic basis of host use inH. v. Plants used in these experiments were tobacco (Nicotiana tabaccum), cotton (Gossypium hirsutum), soybean (Glycine max) (hosts ofH. v.) and ground cherry (Physalis pubescens) (host ofH.s.).
A feeding study ofH.v., H.s. and their reciprocal hybrids showed that, after the first eight days of feeding,H.v. had its highest survival and weight gain on soybean and had lowest survival and weight gain on its non-host,Physalis. H.s. had its highest survival and weight gain on its host plant,Physalis, and performed very poorly on the three non-host plants. The two F1 hybrids were SV0 (offspring ofH.s. female andH.v. male) and VS0 (offspring ofH.v. female andH.s. male). The hybrids did not differ from each other, indicating no sex linkage or maternal effects, except that VS0 had greater weight gain on tobacco than did SV0. The hybrids, unlike their parents, survived well on all four host plants and their weight gain was intermediate on all four
host plants.
In a separate experiment the VS0 hybrid was mated to the specialist to produce the VS1 backcross. In contrast to the F1, the backcross had significantly lower survival than the generalist on soybean, cotton, tobacco and weight gain was lower
on soybean, cotton and tobacco but higher onPhysalis. Survival and weight gain on cotton and tobacco were inherited as partially dominant traits; onPhysalis there was overdominance for survival and complete dominance for weight gain; on soybean both survival and weight gain were
additive. Survival on cotton,Physalis, soybean and tobacco and weight gain onPhysalis could not be completely explained by a model that included only dominance and additive effects. These traits may be influenced
by epistatic and/or environmental effects. |
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Keywords: | Heliothis subflexa generalist specialist genetics hybrids dominance |
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