Transmission strategy is correlated with pathogenicity and disparate virulence and productivity traits in an insect nucleopolyhedrovirus

Abstract

Trabajo presentado en la 43rd Annual Meeting of the Society for Invertebrate Pathology y 10th International Colloquium on Invertebrate Pathology, celebrado en Trabzon (Turquía) del 11 al 15 de julio de 2010. The Final Meeting of COST862 Action: Bacterial Toxins for Insect Control.The prevalence of sublethal infections of Spodoptera exigua multiple nucleopolyhedrovirus (SeMNPV) was quantified in natural populations of S. exigua in Almeria, Spain, during 2006 and 2007. Of 1045 adults collected, 16% proved positive for viral polyhedrin gene transcripts by RT-PCR. The prevalence of covert infection varied significantly according to sex and sample date. Of 1660 progeny of field-collected insects, lethal disease was observed in 10-33% of offspring of transcript-positive females and 9-49% of offspring of transcript-negative females. Isolates associated with vertically-transmitted infections were characterized by restriction endonuclease analysis using BglII and compared with isolates believed to be horizontally-transmitted. Insects from a sublethally-infected Almerian colony were ~3.4-fold more susceptible to infection than healthy insects from a Swiss colony. Horizontally-transmitted isolates were significantly more pathogenic than vertically-transmitted isolates in insects from both colonies. Mean speed of kill varied between isolates by >20 h, whereas mean occlusion body (OB) production varied by 3.8-fold among isolates. Intriguingly, all three horizontally transmitted isolates were very similar in speed of kill and OB production, whereas all three vertically transmitted isolates differed significantly from one another in both variables, and also differed significantly from the group of horizontally-transmitted isolates in one or both variables. We conclude that key pathogenicity and virulence traits of SeMNPV isolates vary according to their principal transmission strategy.Peer Reviewe