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)

Abstract

BACKGROUNDTrichogramma 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.RESULTSA medium clutch size of 42.75 to 62.27 for TdB and 52.93 to 57.14 for TdT was optimal to maximize fitness‐correlated traits of parasitoid individual. The optimal clutch sizes with maximized parameters included adult emergence rate, adult body size, adult longevity, fecundity, and sum of fecundity of all females per brood were 58.31 (86.00%), 42.75 (231.11 μm), 50.92 (2.69 days), 62.27 (150.89 eggs), and 83.25 (7926.33 eggs) for TdB and 57.14 (94.54%), 52.93 (236.97 μm), 53.64 (2.62 days), 56.80 (161.01 eggs), and 70.10 (8579.71 eggs) for TdT. The TdT had a shorter adult longevity, longer development time, and higher adult emergence rate than did its non‐infected bisexual counterpart.CONCLUSIONA medium brood size in a A. pernyi egg host was optimal to produce offspring parasitoids with higher fitness parameters for both bisexual Wolbachia‐uninfected and thelytokous Wolbachia‐infected lines of T. dendrolimi. The determination of optimal clutch size for T. dendrolimi will provide the reference for the quality control of T. dendrolimi production and improvement of the field performance of the wasps. © 2020 Society of Chemical Industry

Effects of Thelytokous Parthenogenesis-Inducing Wolbachia on the Fitness of Trichogramma dendrolimi Matsumura (Hymenoptera: Trichogrammatidae) in Superparasitised and Single-Parasitised Hosts

“…Vavre et al (1999) also reported the presence of the A subdivision of Wolbachia increases fecundity of Trichogramma bourarachae Pintureau and Babault. However, others showed Wolbachia has negative effects on host fitness in most occasions, including lower emergence rate, shorter longevity, smaller body size, and lower fecundity, when compared to their uninfected counterparts (Stouthamer and Luck, 1993;Hohmann et al, 2001;Tagami et al, 2001;Miura and Tagami, 2004;Russell and Stouthamer, 2011;Zhou et al, 2020). Previous studies also 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).…”

“…Considering these two opposite hypotheses, an important question that should be tested arises: is the effect of Wolbachia on the fitness of Trichogramma offspring positive or negative in superparasitised hosts? Although previous studies have shown that Trichogramma infected by Wolbachia have higher probability for superparasitism (Huigens et al, 2004b;Farahani et al, 2015;Zhou et al, 2019bZhou et al, , 2020, the fate of Trichogramma offspring in the superparasitised host is still unknown.…”

“…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, 2019bZhou et al, , 2020. Rahimi-Kaldeh et al (2017) found that Wolbachia infection increases fecundity of thelytokous Trichogramma brassicae Bezdenko.…”

Selection and evaluation of qPCR reference genes for expression analysis in the tiny egg parasitoid wasp,Trichogramma dendrolimiMatsumura (Hymenoptera: Trichogrammatidae)

“…Among all the Trichogramma species, Trichogramma dendrolimi is considered an important egg parasitoid of a broad range of pests [3–6]. In China, the use of T. dendrolimi for controlling Lepidopteran pests is particularly inexpensive due to it being reared on the eggs of Chinese oak silk moth ( Antheraea pernyi ), which is easy to obtain from farmers who rear and collect cocoons of A. pernyi for the textile industry and can support the development of approximately in the tens to hundreds of offspring wasps per egg [7–10]. Therefore, the inundative release of T. dendrolimi wasps is an increasingly important, efficient, and environmentally friendly measure to control Lepidopteran pests that has been applied across millions of hectares annually in the crop-producing areas of China [2].…”

“…As important biological control agents, the biological characteristics of Trichogramma spp. have been studied in detail [2,10,11], and current investigations should focus on the molecular biology of Trichogramma . Although the whole genomes of Trichogramma , including T. pretiosum, T. brassicae , and T. evanescens , have been well annotated [12–14], the regulatory mechanisms of these tiny parasitoids is poorly researched.…”