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The genetic basis of host range in Heliothis virescens: larval survival and growth

Sheck, A.L., Gould, F.
Entomologia experimentalis et applicata 1993 v.69 no.2 pp. 157-172
Glycine max, Gossypium hirsutum, Heliothis subflexa, Heliothis virescens, Nicotiana tabacum, Physalis pubescens, additive effect, backcrossing, cotton, dominance (genetics), environmental impact, epistasis, females, host plants, host range, hybrids, larvae, males, maternal effect, models, overdominance, parents, progeny, sex linkage, soybeans, tobacco, weight gain
Larval feeding was assayed in a generalist caterpillar (Heliothis virescens (F.)), a specialist caterpillar (Heliothis subflexa (Gn.)), their F₁ hybrids and a backcross with H.s. to gain a preliminary understanding of the genetic basis of host use in H.v. Plants used in these experiments were tobacco (Nicotiana tabaccum), cotton (Gossypium hirsutum), soybean (Glycine max) (hosts of H.v.) and ground cherry (Physalis pubescens) (host of H.s.). A feeding study of H.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 of H.s. female and H.v. male) and VS₀ (offspring of H.v. female and H.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 on Physalis. Survival and weight gain on cotton and tobacco were inherited as partially dominant traits; on Physalis 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 on Physalis 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.