Co-occurrence of thelytokous and bisexual Trichogramma dendrolimi Matsumura (Hymenoptera: Trichogrammatidae) in a natural population

Abstract

Trichogramma dendrolimi is one of the most successful biocontrol agents in China. However, an inundative condition is necessary to obtain acceptable parasitism effect. A good solution to this is the application of its thelytokous counterparts which unfortunately are scarce in field. We here report the first case of a natural T. dendrolimi population in China comprising both bisexual wasps and an extremely low proportion of thelytokous wasps. These two forms of T. dendrolimi are phylogenetically related based on the reconstructions of ITS-2 and COI genes. Also, the phylogenetic results suggested a potentially Wolbachia-drived ITS-2 variation. The expression of thelytoky was hardly affected by temperature, which might help control Asian corn borer and Dendrolimus punctatus. Wolbachia are responsible for current thelytoky according to phylogenetic analyses, antibiotic treatment and introgression experiment. We also present the third case of paternal sex ratio chromosome that restrains the expansion of Wolbachia. Moreover, the low frequency of thelytoky may be common in natural populations. Consequently if for biological control it is determined that a thelytokous strain is to be preferred, then large number of field collected females should be set up as isofemale lines, to detect the rare thelytoky.

Wolbachia‐infected Trichogramma dendrolimi is outcompeted by its uninfected counterpart in superparasitism but does not have developmental delay

“…The T. dendrolimi strain of the offspring was identified using the COI sequences of the W strain and B strain of T. dendrolimi. 35 The frequencies of inter-and intrastrain superparasitism were recorded. Proportion survival of W or B offspring was calculated as the number of wasps that emerged from the offspring.…”

Effects of Wolbachia Infection, Parasitic Order, And Time Interval On The Outcome of Inter-Strain Intrinsic Competition Between Bisexual Strain And Wolbachia-Induced Thelytokous Strain of Egg Parasitoid, Trichogramma Dendrolimi

“…The extracted DNA was stored at -20 °C. The COI sequences of each sample were ampli ed using PCR according to the procedure described by Liu et al (2019). The PCR products were sequenced by Invitrogen Trading Co, Ltd. (Shanghai, China).…”

“…The Wolbachia-infected thelytokous strain (TDW) and the Wolbachia-uninfected bisexual strain (TDB) of T. dendrolimi were originally isolated from the eggs of Dendrolimus punctatus (Walker) (Lepidoptera: Lasiocampidae) collected from a forest of Chinese red pine, Pinus massoniana Lamb (Coniferales: Pinaceae), located at the southern end of the Changbai Mountains in Huanren County (125°25 E, 41°10 N), Liaoning Province, China, on April 16, 2017 (Liu et al 2019). The Wolbachia infection of TDW strain was detected using speci c primers (81F: 5 -TGGTCCAATAAGTGATGAAGAAAC-3 and 691R: 5 -AAAAATTAAACGCTACTCCA-3 ) for the wsp gene of Wolbachia (Zhou et al 2020).…”

Spontaneous parthenogenesis in the parasitoid wasp Cotesia typhae: low frequency anomaly or evolving process?

“…Alternatively, thelytoky appears cyclic in some species where asexual generations alternate with sexual ones (Neiman et al, 2014). In other cases, polymorphism in the reproductive mode is observed either between populations (Foray et al, 2013;Leach et al, 2009) or within populations (Liu et al, 2019). Even in such polymorphic situations, thelytokous females usually produce female only progeny, albeit with a very low frequency of males in some cases, allowing rare events of sexual reproduction (Pijls et al, 1996).…”