Abstract
ThelytokousWolbachia-infectedTrichogrammaspecies have long been considered as biological control agents against lepidopteran pests in agriculture and forestry.Wolbachiahas been suggested to increase the probability of the superparasitism ofTrichogramma, but the fate of infected offspring in the superparasitised host is still unknown. The present study aimed to evaluate the fitness of thelytokousWolbachia-infected (TDW) and bisexualWolbachia-free (TD)Trichogramma dendrolimiMatsumura (Hymenoptera: Trichogrammatidae) lines in superparasitised or single-parasitised hosts. The results showed that irrespective of whetherTrichogrammawasps were developed from superparasitised or single-parasitised hosts, the TDW line was characterized by reduced fitness, including lower fecundity, shorter longevity, and smaller body size of F1 offspring, and lower emergence rate of F2 offspring than the TD line. This was not true for the survival rate and developmental time of F1 offspring. Additionally, the fitness parameters ofT. dendrolimithat developed from superparasitised hosts were lower compared with that ofT. dendrolimithat developed from single-parasitised hosts. Interestingly,Wolbachia-infected females had higher dispersal capacity than bisexual females when they developed from superparasitised hosts. The results indicated thatWolbachianegatively affects fitness ofT. dendrolimi, but enhance dispersal capacity ofT. dendrolimifemales in superparasitism condition. Further studies need to be carried out to select the best line that will allowWolbachiaand their hostTrichogrammato be better adapted to one another.
Highlights
The egg parasitoids Trichogramma spp. have been widely used worldwide to control lepidopteran pests in agriculture and forestry (Li, 1994; Smith, 1996; Wang et al, 2019; Zhou et al, 2019a,b; Zang et al, 2020)
The survival rate of F1 offspring was not affected by the parasitism type (χ2 = 2.19, df = 1, P = 0.14), the T. dendrolimi line (χ2 = 3.68, df = 1, P = 0.055), or their interaction (χ2 = 0.073, df = 1, P = 0.79) (Figure 1)
The body size of F1 female offspring was significantly affected by the parasitism type (χ2 = 205.59, df = 1, P < 0.001) and the T. dendrolimi line (χ2 = 7.08, df = 1, P = 0.0078), but it was not affected by their interaction (χ2 = 0.39, df = 1, P = 0.53)
Summary
The egg parasitoids Trichogramma spp. have been widely used worldwide to control lepidopteran pests in agriculture and forestry (Li, 1994; Smith, 1996; Wang et al, 2019; Zhou et al, 2019a,b; Zang et al, 2020). Thelytokous Trichogramma has advantages in biological control programs including easier colonization without mating and less costly to rear en masse (Stouthamer, 1993; Zhou et al, 2019b, 2020). Previous studies found that Wolbachia is the factor that causes the occurrence of intersex (Bowen and Stern, 1966; Beserra et al, 2003; Tulgetske and Stouthamer, 2012; Ning et al, 2019). In these cases, thelytokous Trichogramma have many advantages in biological control programs, the Wolbachia infection may have potential negative consequences on the production of thelytokous Trichogramma
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