rna-interference-egg-parasitoid-trichogramma-dendrolimi

RNA Interference in the Egg Parasitoid, <em>Trichogramma dendrolimi</em> Matsumura

The egg parasitoids, Trichogramma spp, are recognized as efficient biological control agents against various lepidopteran pests in agriculture and ...

Shenyang Agricultural University

Thelytokous Wolbachia-infected Trichogramma spp. are widely used egg parasitoids against lepidopteran pests in biological control programs. Wolbachia may manipulate host wasps for superparasitism and is sensitive to temperature. To explore effects of temperature and superparasitism, we compared fitness parameters and Wolbachia-mediated phenotype of thelytokous Wolbachia-infected Trichogramma dendrolimi between those emerging from superparasitised or single-parasitised hosts at 17, 21, 25, or 29 °C. Infected mothers of T. dendrolimi showed reduced superparasitism and parasitism increased with temperature. Wolbachia titre decreased with temperature when females emerged from singly-parasitised hosts, but there was no correlation in superparasitised hosts. Females showed higher Wolbachia titres at 21, 25, or 29 °C when developing from superparasitised hosts. The daily male ratio of offspring increased with temperature, and the day-age threshold for 5%, 50%, or 95% daily male ratio decreased with temperature in both parasitism forms. Females that emerged from superparasitised hosts had a shorter life span and reduced fecundity. These results indicate that Wolbachia may affect host behaviour by increasing superparasitism to enhance its spread, but this has negative effects on thelytokous Wolbachia-infected T. dendrolimi.

Effects of temperature and superparasitism on quality and characteristics of thelytokous Wolbachia-infected Trichogramma dendrolimi Matsumura (Hymenoptera: Trichogrammatidae) during mass rearing.

Trichogramma dendrolimi has been widely used in augmentative biocontrol of lepidopteran pests in China. In mass production of T. dendrolimi using Antheraea pernyi eggs as substitutive hosts, which are large in size, as clutch size is a parameter of importance to produce high quality parasitoids. Here, we aimed to determine the optimal clutch size for the bisexual Wolbachia-uninfected line (TdB) and Wolbachia-infected thelytokous line (TdT) of T. dendrolimi reared on A. pernyi eggs.

Optimal clutch size for quality control of bisexual and Wolbachia-infected thelytokous lines of Trichogramma dendrolimi Matsumura (Hymenoptera: Trichogrammatidae) mass reared on eggs of a substitutive host, Antheraea pernyi Guérin-Méneville (Lepidoptera: Saturniidae).

The bacterial endosymbiont,  spp. induce thelytokous parthenogenesis in certain parasitoid wasps, such as the egg parasitoid wasps  spp. To complete the cycle of vertical transmission,  displays efficient transovarial transmission by targeting the reproductive tissues and often exhibits strong tissue-specific tropism in their host.

Posterior concentration of  during the early embryogenesis of the host dynamically shapes the tissue tropism of  in host  wasps.

  wasps are egg parasitoids of agricultural lepidopteran pests. The sex of  is determined by its ploidy as well as certain sex ratio distorters, such as the endosymbiotic bacteria  spp. and the paternal sex ratio (PSR) chromosome. The sex determination systems of hymenopterans, such as  spp., involve cascades of the genes  (), - (), and  () and are associated with sex-specific  and  splicing. First, these genes and their sex-specific variants must be identified to elucidate the interactions between the sex ratio disorders and the sex determination mechanism of .  Here, we characterized the sex determination genes , , and  in . Sex-specific  and  variants were detected in cDNA samples obtained from both male and female  wasps. They were observed in the early embryos (1-10 h), late embryos (12-20 h), larvae (32 h and 48 h), pre-pupae (96 h), and pupae (144 h, 168 h, 192 h, and 216 h) of both male and female  offspring.  We detected female-specific  variants throughout the entire early female offspring stage. The male-specific variant began to express at 9-10 h as the egg was not fertilized. However, we did not find any maternally derived, female-specific  variant in the early male embryo. This observation suggests that the female-specific  variant expressed in the female embryo at 1-9 h may not have originated from the maternal female wasp.  The present study might be the first to identify the sex determination genes and sex-specific gene splicing in  wasps. The findings of this study lay the foundation for investigating the sex determination mechanisms of  and other wasps. They also facilitate sex identification in immature  and the application of this important egg parasitoid in biological insect pest control programs.

The identification and expression pattern of the sex determination genes and their sex-specific variants in the egg parasitoid  Matsumura (Hymenoptera: Trichogrammatidae).

Wu-nan Che

College of Plant Protection

Shenyang Agricultural University

RNA Interference in the Egg Parasitoid, Trichogramma dendrolimi Matsumura