Does Wolbachia Infection Change the Overwintering Ability of Trichogramma brassicae (Hymenoptera: Trichogrammatidae)?

Hybrid Genome Assembly and Evidence-Based Annotation of the Egg Parasitoid and Biological Control Agent Trichogramma brassicae

Trichogramma brassicae (Bezdenko) are egg parasitoids that are used throughout the world as biological control agents and in laboratories as model species. Despite this ubiquity, few genetic resources exist beyond COI, ITS2, and RAPD markers. Aided by a Wolbachia infection, a wild-caught strain from Germany was reared for low heterozygosity and sequenced in a hybrid de novo strategy, after which several assembling strategies were evaluated. The best assembly, derived from a DBG2OLC-based pipeline, yielded a genome of 235 Mbp made up of 1,572 contigs with an N50 of 556,663 bp. Following a rigorous ab initio-, homology-, and evidence-based annotation, 16,905 genes were annotated and functionally described. As an example of the utility of the genome, a simple ortholog cluster analysis was performed with sister species T. pretiosum, revealing over 6000 shared clusters and under 400 clusters unique to each species. The genome and transcriptome presented here provides an essential resource for comparative genomics of the commercially relevant genus Trichogramma, but also for research into molecular evolution, ecology, and breeding of T. brassicae.

Animal-Microbe Interactions in the Context of Diapause

Dormancy and diapause are key adaptations in many organisms, enabling survival of temporarily or seasonally unsuitable environmental conditions. In this review, we examine how our understanding of programmed developmental and metabolic arrest during diapause intersects with the increasing body of knowledge about animal co-development and co-evolution with microorganisms. Host-microbe interactions are increasingly understood to affect a number of metabolic, physiological, developmental, and behavioral traits and to mediate adaptations to various environments. Therefore, it is timely to consider how microbial factors might affect the expression and evolution of diapause in a changing world. We examine how a range of host-microbe interactions, from pathogenic to mutualistic, may have an impact on diapause phenotypes. Conversely, we examine how the discontinuities that diapause introduces into animal host generations can affect the ecology of microbial communities and the evolution of host-microbe interactions. We discuss these issues as they relate to physiology, evolution of development, local adaptation, disease ecology, and environmental change. Finally, we outline research questions that bridge the historically distinct fields of seasonal ecology and host-microbe interactions.

Abiotic and biotic factors influence diapause induction in sexual and asexual strains of Trichogramma brassicae (Hym: Trichogrammatidae)

The effects of some abiotic (maternal photoperiod and offspring developmental temperature) and biotic (host quality during both maternal and offspring generations) factors on diapause induction were investigated for two sympatric strains of Trichogramma brassicae Bezdenko (Hym: Trichogrammatidae) differing by infection status with regard to Wolbachia. The mode of reproduction, developmental temperature, maternal photoperiod and the quality of the host significantly affected diapause induction. The highest percentage of diapausing individuals were observed with the sexual strain reared at 14 °C using a “high quality” host and after a long photophase during the maternal generation. Environment-by-Environment, as well as Genotype-by-Environment interactions, was observed. All these patterns were discussed with the goal of providing relevant protocols for the commercial mass-rearing of such biocontrol agents. A successful diapause in beneficial insects could affect the efficiency of mass rearing by increasing the duration of storage conditions based on a high percent emergence and providing a large number of individuals at the appropriate time in the field season.