The biology of Meteorus gyrator (Hymenoptera: Braconidae), a solitary endoparasitoid of the tomato moth, Lacanobia oleracea (Lepidoptera: Noctuidae)

Effects of Galanthus nivalis agglutinin (GNA) expressed in tomato leaves on larvae of the tomato moth Lacanobia oleracea (Lepidoptera: Noctuidae) and the effect of GNA on the development of the endoparasitoid Meteorus gyrator (Hymenoptera: Braconidae)

The effect of ingestion of transgenic tomato leaves expressing the plant lectin Galanthus nivalis agglutinin (GNA) on development of larvae of Lacanobia oleracea (Linnaeus) was studied under laboratory conditions. When L. oleracea larvae were fed on tomato line 14.1H, expressing approximately 2.0% GNA, significant increases in the mean larval weight and in the amount of food consumed were found. This resulted in an overall reduction in the mean development time to the pupal stage of approximately 7 days. A significant increase in the percentage survival to the adult moth was also recorded when newly hatched larvae were reared on transgenic tomato leaves (72%) compared to larvae reared on untransformed leaves (40%). The effects of ingestion of GNA by L. oleracea larvae, via artificial diet or the leaves of transgenic tomato or potato plants, on the subsequent development of its solitary endoparasitoid Meteorus gyrator (Thunberg) was also studied. No significant effects on the life cycle parameters of M. gyrator developing in L. oleracea fed on GNA-containing diets were observed. Experiments with transgenic potato plants indicated that the stadium of the host larvae at parasitism had a greater influence on M. gyrator development than the presence of GNA. Potential GNA-binding glycoproteins were detected in the gut and body tissues of larval M. gyrator. Despite detection in host tissues, GNA could not be detected in adult M. gyrator and therefore it is likely that at the time of pupation M. gyrator are able to void the GNA in the meconial pellet.

Interactions between the solitary endoparasitoid, Meteorus gyrator (Hymenoptera: Braconidae) and its host, Lacanobia oleracea (Lepidoptera: Noctuidae), infected with the entomopathogenic microsporidium, Vairimorpha necatrix (Microspora: Microsporidia)

Infection of Lacanobia oleracea (Linnaeus) larvae with the microsporidium Vairimorpha necatrix (Kramer) resulted in significant effects on the survival and development of the braconid parasitoid, Meteorus gyrator (Thunberg). Female M. gyrator did not show any avoidance of V. necatrix-infected hosts when they were selecting hosts for oviposition. When parasitism occurred at the same time as infection by the pathogen, or up to four days later, no significant detrimental effects on the parasitoid were observed. However, when parasitism occurred six to eight days after infection, a greater proportion (12.5-14%) of hosts died before parasitoid larvae egressed. Successful eclosion of adult wasps was also reduced. When parasitism and infection were concurrent, parasitoid larval development was significantly faster in infected hosts, and cocoons were significantly heavier. However, as the time interval between infection and parasitism increased, parasitoid larval development was significantly extended by up to two days, and the cocoons formed were significantly (c. 20%) smaller. Vairimorpha necatrix spores were ingested by the developing parasitoid larvae, accumulated in the occluded midgut, and were excreted in the meconium upon pupation.