Constitutive and herbivore‐induced structural defenses are compromised by inbreeding in Solanum carolinense (Solanaceae)

Abstract

Constitutive and induced structural defenses in horsenettle were negatively affected by inbreeding. Reduced flower production and internode length on damaged plants compared to controls suggests that defense induction entails significant costs.

Leaf trichomes affect caterpillar feeding in an instar-specific manner

“…For example, we previously documented that M. sexta feeding on older leaves of Solanum carolinense induced a higher density of stellate trichomes (branched non-glandular trichomes with spikes) on both surfaces of new leaves after 21 days [5]. In the same system, we also demonstrated that non-glandular stellate trichomes cause physical injury to caterpillars and impede the ability of early instar caterpillars to locate the epidermis and commence feeding [3].…”

“…Common horsenettle ( Solanum carolinense ) is a perennial shrub considered a noxious weed in its native range of eastern North America [3,5]. Multiple genets of S. carolinense plants used in this study were derived from the outcrossed fruits of 3–5 parental plants taken from a natural population near State College, PA, USA [21].…”

“…Multiple genets of S. carolinense plants used in this study were derived from the outcrossed fruits of 3–5 parental plants taken from a natural population near State College, PA, USA [21]. Seedlings of S. carolinense were transplanted to 15 cm pots after 3–4 weeks, and allowed to grow for 3–4 more weeks in a growth chamber (16: 8 Light and dark cycle, 23C, and 50% relative humidity) before used in experiments (For more details, see [3,5,21]).…”

“…For example, two commonly cultivated species, Solanum lycopersicon (tomato) and Nicotiana tabacum (tobacco), have multiple types of glandular trichomes [7,9,13], whereas the common non-domesticated weeds Solanum elaeagnifolium and Solanum carolinense are devoid of any glandular trichomes, but have a dense mat of non-glandular stellate trichomes [3,5,14], (Figure 1). Here using multiple species from Solanaceae, we examined the effects of trichome type X M. sexta larval instar on feeding initiation.

10.1080/19420889.2018.1486653-F0001Figure 1.(a) Trichome morphology of S. eleaegnifolium.

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Inbreeding compromises host plant defense gene expression and improves herbivore survival

“…leaf trichomes), another defense trait negatively affected by inbreeding. 25 Compromised anti-herbivore defense gene expression may explain why other studies have shown that inbred host plants are more likely to be attacked by herbivores than outbred plants and herbivores often perform better when they feed on inbred plants. 26,15 It also might explain why inbred plants are preferred in choice experiments by both M. sexta larvae 12,10 and ovipositing females.…”