Abstract
The American bollworm Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) is a highly destructive agriculture pest of worldwide importance. The aim of the present study was to infect H. armigera larvae with entomopathogenic nematode juveniles for hematological study of proteins and encapsulation responses to evaluate using this nematode for the management of this pest. Total protein estimation and the electrophoretic profiling carried out in the hemolymph showed a high pathogenicity of Steinernema abbasi to H. armigera. The control group survived and succeeded to develop to adults, while the infected ones died within 24 h. An increase in the protein contents in the total and plasma hemolymph was observed just after 3 h of infection with an increase at 6 h and 9 h as symptoms of early defence of the insect. SDS-PAGE profile also showed an evolvement of a protein band of 46 kDa. No self-association or aggregation and binding of other proteins were found in the hemolymph as revealed by Native-PAGE. The encapsulation avoidance rate of nematode juvenile gave good results with (> 33%) in 2 IJs/larva to 5% in 20 IJs/larva doses at24 h post infection. Loss of hemolymph proteins continued for more than 24 h with a very low recognition of nematode rate in hemolymph, followed by the death of larvae within 48 h, which proved the high pathogenicity of S. abbasi and suppression of host immune system of H. armigera.
Highlights
Insect immunology is a rapidly growing discipline with exciting and innovative application, especially in control of agricultural pests by understanding the host parasite interactions such as entomopathogenic nematodes (EPNs)
When the nematode enters in the hemocoel of insect, soluble proteins in hemolymph and proteins released by hemocytes and hematopoietic organs participate in their encapsulation (Lemaitre and Hoffmann 2007)
Analysis of variance showed that total protein contents in total hemolymph challenged with S. abbasi was affected by time and not by treatment
Summary
Insect immunology is a rapidly growing discipline with exciting and innovative application, especially in control of agricultural pests by understanding the host parasite interactions such as entomopathogenic nematodes (EPNs). When insect pests of agricultural crops are targeted by microorganisms, they rely on innate immunity for quick response comprises cellular and humoral activity. Researchers showed that the nematodes, and the bacterial symbionts are highly pathogenic to many insect pests once they reached the hemocoel of the insect (Forst and Nealson 1996). During their complex life cycle in a common insect host, bacteria carried by the nematodes in their gut are regurgitated in the hemocoel of insect, where they multiply along with nematodes and produced several toxins, leading to the death of insect. Little information is available about the nematode infection and hematological changes in H. armigera
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