Parasitism by the endoparasitoid, Cotesia flavipes induces cellular immunosuppression and enhances susceptibility of the sugar cane borer, Diatraea saccharalis to Bacillus thuringiensis

Abstract

Cotesia flavipes Cameron (Hymenoptera: Braconidae), is a gregarious larval endoparasitoid of the sugarcane borer, Diatraea saccharalis Fabricius (Lepidoptera: Crambidae). The aim of this research was to analyze cellular immunosuppression of D. saccharalis parasitized by C. flavipes in terms of encapsulation, melanization, and hemocyte nodule formation. The encapsulation assay was done 1 and 6 days after parasitoid oviposition. In addition, the susceptibility of parasitized and nonparasitzed larvae to Bacillus thuringiensis HD 73 strain was assessed. 3, 12, and 24 h after bead injection; the percentages of encapsulation were significantly higher in unparasitized larvae compared to larvae parasitized 1 and 6 days after oviposition. Interestingly, there was a significant reduction in numbers of beads encapsulated at 1 day after oviposition compared to 6 days, and unparasitized larvae. The percentage of melanized beads decreased significantly in parasitized larvae compared to control. There was a reduction in the number of nodules in parasitized larvae compared to unparasitized controls. Larvae that were injected with polyndavirus 24 h before beads were injected showed significantly reduced encapsulation responses relative to control larvae. The D. saccharalis parasitized by C. flavipes exhibited higher susceptibility to B. thuringiensis. These results suggest that parasitization induced host immunosuppression, and the immunosuppression factors could impair the defense capacity against microbial pathogens - causing an increase in pathogen susceptibility.

Keywords: cellular immunity, encapsulation, nodulation, polydnavirus

Abbreviations: LD, linkage disequilibrium

Correspondence: ^a alialimh@yahoo.com, ^b ericklusan@yahoo.com, ^c drmarodriguez@hotmail.com, *Corresponding author

Editor: Michael Strand was Editor of this paper.

Received: 13 November 2010 | Accepted: 27 January 2011 | Published: 17 September 2011

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 11, Number 119

Mahmoud A.M.A, de Luna-Santillana E.J., Rodríguez-Perez M.A. 2011. Parasitism by the endoparasitoid, Cotesia flavipes induces cellular immunosuppression and enhances susceptibility of the sugar cane borer, Diatraea saccharalis to Bacillus thuringiensis. Journal of Insect Science 11:119 available online: insectscience.org/11.119