Subterranean, herbivore-induced plant volatile increases biological control activity of multiple beneficial nematode species in distinct habitats

While the role of herbivore-induced volatiles in plant-herbivore-natural enemy interactions is well documented aboveground, new evidence suggests that belowground volatile emissions can protect plants by attracting entomopathogenic nematodes (EPNs). However, due to methodological limitations, no study has previously detected belowground herbivore-induced volatiles in the field or quantified their impact on attraction of diverse EPN species. Here we show how a belowground herbivore-induced volatile can enhance mortality of agriculturally significant root pests. First, in real time, we identified pregeijerene (1,5-dimethylcyclodeca-1,5,7-triene) from citrus roots 9-12 hours after initiation of larval Diaprepes abbreviatus feeding. This compound was also detected in the root zone of mature citrus trees in the field. Application of collected volatiles from weevil-damaged citrus roots attracted native EPNs and increased mortality of beetle larvae (D. abbreviatus) compared to controls in a citrus orchard. In addition, field applications of isolated pregeijerene caused similar results. Quantitative real-time PCR revealed that pregeijerene increased pest mortality by attracting four species of naturally occurring EPNs in the field. Finally, we tested the generality of this root-zone signal by application of pregeijerene in blueberry fields; mortality of larvae (Galleria mellonella and Anomala orientalis) again increased by attracting naturally occurring populations of an EPN. Thus, this specific belowground signal attracts natural enemies of widespread root pests in distinct agricultural systems and may have broad potential in biological control of root pests.info:eu-repo/semantics/publishedVersio

Prophenoloxidase from Pieris rapae: gene cloning, activity, and transcription in response to venom/calyx fluid from the endoparasitoid wasp Cotesia glomerata *

Prophenoloxidase (PPO) plays an important role in melanization, necessary for defense against intruding parasitoids. Parasitoids have evolved to inject maternal virulence factors into the host hemocoel to suppress hemolymph melanization for the successful development of their progeny. In this study, the full-length complementary DNA (cDNA) of a Pieris rapae PPO was cloned. Its cDNA contained a 2 076-base pair (bp) open reading frame (ORF) encoding 691 amino acids (aa). Two putative copper-binding sites, a proteolytic activation site, three conserved hemocyanin domains, and a thiol ester motif were found in the deduced amino acid sequence. According to both multiple alignment and phylogenetic analysis, P. rapae PPO gene cloned here is a member of the lepidopteran PPO-2 family. Injection of Cotesia glomerata venom or calyx fluid resulted in reduction of P. rapae hemolymph phenoloxidase activity, demonstrating the ability to inhibit the host′s melanization. Real-time reverse transcriptase polymerase chain reaction (RT-PCR) showed that transcripts of P. rapae PPO-2 in the haemocytes from larvae had not significantly changed following venom injection, suggesting that the regulation of PPO messenger RNA (mRNA) expression by venom was not employed by C. glomerata to cause failure of melanization in parasitized host. While decreased P. rapae PPO-2 gene expression was observed in the haemocytes after calyx fluid injection, no detectable transcriptional change was induced by parasitization, indicating that transcriptional down-regulation of PPO by calyx fluid might play a minor role involved in inhibiting the host′s melanization