A comparative study on the functional response of Wolbachia-infected and uninfected forms of the parasitoid wasp Trichogramma brassicae
1Biological Control Research Department, Iranian Research Institute of Plant Protection,
P. O. Box, 1454, Tehran 19395, Iran
2Department of Plant Protection, College of Agriculture, University of Tehran, Karaj 31587-11167, Iran
3Laboratory of Entomology, Wageningen University, P.O. Box, 8031, 6700 EH, Wageningen, The Netherlands
Abstract
Trichogramma species (Hymenoptera: Trichogrammatidae) are haplo-diploid egg parasitoids that are frequently used as biological control agents against lepidopteran pests. These wasps display two reproductive modes, including arrhenotoky (bisexuality) and thelytoky (unisexuality). Thelytokous forms are often associated with the presence of endosymbiotic Wolbachia bacteria. The use of thelytokous wasps has long been considered as a way to enhance the efficacy of biological control. The present study investigates the potential of a thelytokous Wolbachiainfected and an arrhenotokous uninfected Trichogramma brassicae Bezdenko strain as inundative biocontrol agents by evaluating their functional response towards different egg densities of the factitious host, the Angoumois grain moth, Sitotroga cerealella (Olivier) (Lepidoptera: Gelechiidae). The results revealed a type II functional response for both strains in which parasitism efficiency decreases with host egg density because of an increasing host handling time. A model with an indicator variable was used to compare the parameters of Holling’s disc equation in different data sets. It was demonstrated that the two strains did not differ in host attack rate. However, the Wolbachia-infected strain did have an increased host handling time when compared to the bisexual strain. Some applied aspects of the findings are discussed.
Keywords: egg parasitoid, endosymbiotic bacterium, attack rate, handling time, thelytokous strain, biological control,
Sitotroga cerealella
Abbreviations: a, attack rate or instantaneous search rate; B, Wolbachia-uninfected strain collected from Baboulsar;
BCRD, Biological Control Research Department; BW+, Wolbachia-infected strain collected from Baboulsar; IRIPP,
Iranian Research Institute of Plant Protection; ITS-2, internal transcribed spacer 2 region; Na, number of parasitized
hosts; N0; initial host density; PI, parthenogenesis inducing; T, total available searching time; Th, handling time per host;
wsp, Wolbachia surface protein gene
Correspondence:
ashahram.farrokhi@gmail.com,
bashouri@ut.ac.ir,
cshirazi@iripp.ir,
dallahyari@ut.ac.ir,
eties.huigens@wur.nl
Associate Editor: J. P. Michaud was editor of this paper.
Received: 20 April 2009 | Accepted: 24 September 2009 | Published: 1 October 2010
Copyright: This is an open access paper. We use the Creative Commons Attribution 3.0 license that permits unrestricted use, provided that the paper is properly attributed.
ISSN: 1536-2442 | Volume 10, Number 167
Farrokhi S, Ashouri A, Shirazi J, Allahyari H, Huigens ME. 2010. A comparative study on the functional response of Wolbachia-infected and uninfected forms of the parasitoid wasp Trichogramma brassicae. Journal of Insect Science 10:167, available online: insectscience.org/10.167
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