Host plant direct defence against eggs of its specialist herbivore, Heliothis subflexa

Abstract

1. The insect Heliothis subflexa Guenée is a specialist on plants in the genus Physalis. In the present study, the physical response of Physalis leaves to egg deposition by H. subflexa is described.2. It was observed that the leaves of Physalis plants respond to the eggs of H. subflexa, while co-occurring non-host plants do not. Leaves of Physalis angulata L. and Physalis pubescens L. respond to H. subflexa eggs by the formation of (i) necrotic tissue, (ii) undifferentiated cells that form a bump (neoplasm) under the eggs of this herbivore, or (iii) both types of responses.3. Greenhouse experiments showed that 64% of eggs laid on P. angulata elicited a response, and that a response to an egg decreased the probability of hatching. Further experiments in the field with P. angulata showed that the mean response to eggs by leaves was 31%, and that this response increased as temperature increased. Field experiments also confirmed that a plant response to an egg decreased the probability of hatching and increased the probability of removal from the plant by physical dislodgement or predation.4. Eggs that elicited a response had a 25% lower probability of hatching and a 28% lower probability of remaining on the plant, resulting in an average fitness cost of 19.3% for H. subflexa. This is the first study to show an induced direct physical defence of a plant against eggs of a noctuid moth.

Perception, signaling and molecular basis of oviposition-mediated plant responses

“…Eggs of the white-backed planthopper Sogatella   furcifera trigger a watery lesion accompanied by dark brownish discoloration in the Reiho rice variety but not in others (Suzuki et al 1996). Eggs of Heliothis subflexa , a specialist noctuid moth that is adapted to Physali s sp., induce necrosis on P.   angulata and P.   pubescens leaves but not on non-host plants (Petzold-Maxwell et al 2011). Brassica nigra plants respond differently to oviposition by the specialist P. brassicae and the generalist Mamestra brassicae .…”

“…For years, plants were only considered as an inert substrate for oviposition but several studies demonstrated that, upon recognition of egg-derived specific elicitors, plants trigger direct defenses or indirect defenses. Briefly, direct defenses consist notably of necrosis on oviposited leaves that restricts egg attachment, hatching or development (Shapiro and DeVay 1987; Balbyshev and Lorenzen 1997), tumor-like structures called “neoplasm” derived from cell division of undifferentiated tissue that lifts the eggs and presumably reduces egg or larval survival (Doss et al 2000; Cooper et al 2005; Petzold-Maxwell et al 2011), the massive growth of wound tissue that crushes beetle eggs (Desurmont et al 2011), the production of toxic molecules like benzyl benzoate (Seino et al 1996; Yamasaki et al 2003) and iridoid glycoside (Peñuelas et al 2006). Indirect defenses include the emission of a bouquet of volatile compounds that attract egg parasitoids.…”

Synergistic effects of direct and indirect defences on herbivore egg survival in a wild crucifer

“…Egg deposition by herbivorous insects has been shown to trigger several plant responses lethal to herbivore eggs, such as (i) hypersensitive response (HR)-like necrosis and neoplasm formation both leading to egg desiccation and egg dropping [31][32][33][34][35], (ii) egg-crushing plant tissue [36] and (iii) ovicidal substances killing eggs [37,38]. At the same time, herbivore eggs may induce indirect defence traits, such as oviposition-induced plant volatiles (OIPVs) or plant cues perceived by contact, that attract or arrest parasitic wasps killing eggs before larvae hatch [29,39].…”

Mechanism of Resistance in Mungbean [Vigna radiata (L.) R. Wilczek var. radiata] to bruchids, Callosobruchus spp. (Coleoptera: Bruchidae)

“…(Watt et al, 1977; Petzold-Maxwell et al, 2011; War et al, 2013). The host plant/seeds avoid insect oviposition either directly or indirectly by killing the insect eggs to avoid hatching of the larvae, thus, preventing future damage (Doss et al, 2000; Petzold-Maxwell et al, 2011). Traits contributing to resistance/susceptibility of mungbean to bruchids include seed color, texture, hardness, size and chemical constituents (Asian Vegetable Research and Development Center [AVRDC], 1979, 1981; Sarikarin et al, 1999; Appleby and Credland, 2003; Lattanzio et al, 2005; Somta et al, 2007).…”