Volatiles Mediating a Plant-Herbivore-Natural Enemy Interaction in Resistant and Susceptible Soybean Cultivars

Abstract

Several studies have shown that herbivore-induced plant volatiles act directly on herbivores and indirectly on their natural enemies. However, little is known about the effect of herbivore damage on resistant and susceptible plant cultivars and its effect on their natural enemies. Thus, the aim of this study was to evaluate the attraction of the herbivorous pentatomid bug Euschistus heros and its egg parasitoid Telenomus podisi to two resistant and one susceptible soybean cultivars with different types of damage (herbivory, herbivory+oviposition, and oviposition). In a Y-tube olfactometer, the parasitoids were attracted to herbivory and herbivory+oviposition damaged soybean plants when compared to undamaged soybean plants for the resistant cultivars, but did not show preference for the susceptible cultivar Silvânia in any of the damage treatments. The plant volatiles emitted by oviposition-damaged plants in the three cultivars did not attract the egg parasitoid. In four-arm-olfactometer bioassays, E. heros females did not show preference for odors of damaged or undamaged soybean plants of the three cultivars studied. The Principal Response Curves (PRC) analysis showed consistent variability over time in the chemical profile of volatiles between treatments for the resistant cultivar Dowling. The compounds that most contributed to the divergence between damaged soybean plants compared to undamaged plants were (E,E)-α-farnesene, methyl salicylate, (Z)-3-hexenyl acetate, and (E)-2-octen-1-ol.

Semiochemicals from plants and insects on the foraging behavior of Platygastridae egg parasitoids

“…The HIPVs and OIPVs vary depending on plant species and cultivars, and influence in different ways the foraging behavior of parasitoids, such as T. podisi that is attracted differently to HIPVs released by three different plant species (Dias, 2015) and soybean cultivars (Michereff et al, 2011). The HIPVs emitted by the resistant soybean cultivars Dowling and IAC 100, in laboratory bioassays, attracted T. podisi, whereas the HIPVs emitted by the susceptible cultivar Silvânia did not (Michereff et al, 2011); a similar result was observed when these cultivars were evaluated in field conditions (Michereff et al, 2015). Therefore, the effect on the third trophic level might be taken into consideration in the development of resistant plant cultivars.…”

“…Furthermore, the chemical profile emitted by herbivore-or oviposition-damaged plants can be markedly different from those of undamaged and mechanically-damaged ones (Moraes et al, , 2008Michereff et al, 2011). This change can be responsible for the differential attraction of parasitoids and predators (Hoballah & Turlings, 2001).…”

“…However, there are still several questions about the importance of these compounds and how they affect the attraction of natural enemies. Most of the pioneering works on HIPVs and their effects on parasitoid behavior were conducted on arable crops, such as maize (Zea mays L.), by Turlings et al (1991) and Takabayashi et al (1995); cotton (Gossypium hirsutum L.), by Turlings et al (1995) and Cortesero et al (1997); rice (Oryza sativa L.), by Lou et al (2005) and Melo Machado et al (2014); soybean, by Moraes et al (2005Moraes et al ( , 2008 and Michereff et al (2011Michereff et al ( , 2013; and bean (Phaseolus vulgaris L.), by Colazza et al (2004).…”

“…Colazza et al (2004) reported that T. basalis is attracted by synomones released by two different legume species, when the plants are damaged by herbivores and oviposition. Different soybean cultivars damaged by E. heros herbivory release a similar chemical profile between them and, in comparison to undamaged soybean plants, produce higher amounts of several compounds, such as (E,E)-α-farnesene, methyl salicylate, (Z)-3-hexenyl acetate, and (E)-2-octen-1-ol (Moraes et al, 2008;Michereff et al, 2011). Olfactometer bioassays conducted with T. podisi and these compounds, in different mixtures and concentrations, showed that this parasitoid responds only to (E,E)-α-farnesene, as a single compound.…”

Defesas induzidas por herbivoria e interações específicas no sistema tritrófico soja-percevejos-parasitoides de ovos

“…A indução de defesas é influenciada pelo hábito de alimentação (sugador ou mastigador) e pelo estágio do inseto herbívoro, bem como por variações genotípicas e fenotípicas da planta (Moraes et al, 2005(Moraes et al, , 2008Michereff et al, 2011).…”