A Generalist Herbivore Copes with Specialized Plant Defence: the Effects of Induction and Feeding by Helicoverpa armigera (Lepidoptera: Noctuidae) Larvae on Intact Arabidopsis thaliana (Brassicales) Plants

Abstract

Plants of the Brassicaceae are defended from feeding by generalist insects by constitutively-expressed and herbivory-induced glucosinolates (GS). We induced Arabidopsis plants 1, 16 and 24 h prior to allowing neonate larvae of the generalist Helicoverpa armigera to feed on whole plants for 72 h. These plants were subsequently retested with another group of neonates for a further 72 h. We used wild-type A. thaliana Col-0, and mutant lines lacking indolic GS, aliphatic GS or all GS. We hypothesized that larvae would not grow well on defended plants (WT) compared to those lacking GS, and would not grow well if plants had been primed or fed on for longer, due to the expected induced GS. There was survivorship on all lines suggesting H. armigera is a suitable generalist for these experiments. Larvae performed less well on wild-type and no indolic lines than on no aliphatic and no GS lines. Larvae distributed feeding damage extensively in all lines, more so on wild type and no-indolic lines. Contrary to expectations, larvae grew better on plants that had been induced for 1 to 16 h than on un-induced plants suggesting they moved to and selected less toxic plant parts within a heterogeneously defended plant. Performance declined on all lines if plants had been induced for 24 h, or had been fed upon for a further 72 h. However, contrary to expectation, individual and total GS did not increase after these two treatments. This suggests that Arabidopsis plants induce additional (not GS) defenses after longer induction periods.

Effect of methyl jasmonate (MeJA)‐induced defenses in rice against the rice leaffolderCnaphalocrocis medinalis(Guenèe) (Lepidoptera: Pyralidae)

“…However, chemical insecticide application against the rice leaf‐folder is not advisable because of pest resistance and resurgence. Furthermore, rice leaf‐folders have a vast array of natural enemies that help maintain their populations below economic loss levels . The rice leaf‐folder has grown in economic importance with the introduction of high‐yielding rice strains and constant cultivation of the crop…”

Moving to Keep Fit: Feeding Behavior and Movement of Helicoverpa armigera (Lepidoptera: Noctuidae) on Artificial Diet With Different Protein: Carbohydrate Ratios

“…Host plants offer a highly heterogeneous nutrient landscape at various scales (Woodwell et al 1975, Eigenbrode and Espelie 1995, Low et al 2014) even in agricultural monocultures (Deans et al 2016). The quality of food an insect eats can be different from plant to plant (Sánchez et al 2004, Tao et al 2014), tissue to tissue (Deans et al 2016), and mouthful to mouthful (Shroff et al 2008), influencing insect movements, development, and survival (Zalucki et al 2002, Perkins et al 2013, Zalucki et al 2017).…”

Trade‐off between defense priming by herbivore‐induced plant volatiles and constitutive defense in tomato

“…In addition, behavioral adaptation to induced plant chemistry may also allow herbivores to bypass HIPV‐primed host defense responses . For instance, Helicoverpa armigera larvae grew better on Arabidopsis plants that had been primed for 1 to 16 h than on unprimed plants, suggesting that the larvae moved to and selected less toxic plant parts of a heterogeneously defended plant . These results suggest that researchers should pay more attention to generalizing about the effects of HIPVs on plant defense and using HIPV‐mediated priming for pest control in agriculture …”