ITS-2 sequences-based identification of Trichogramma species in South America

Abstract

ITS2 (Internal transcribed spacer 2) sequences have been used in systematic studies and proved to be useful in providing a reliable identification of Trichogramma species. DNAr sequences ranged in size from 379 to 632 bp. In eleven T. pretiosum lines Wolbachia-induced parthenogenesis was found for the first time. These thelytokous lines were collected in Peru (9), Colombia (1) and USA (1). A dichotomous key for species identification was built based on the size of the ITS2 PCR product and restriction analysis using three endonucleases (EcoRI, MseI and MaeI). This molecular technique was successfully used to distinguish among seventeen native/introduced Trichogramma species collected in South America.Keywords: molecular markers, ITS-2 sequence, Hymenoptera, egg parasitoid. Identificação molecular de espécies de Trichogramma na América do Sul via sequenciamento da região ITS-2 ResumoSequências do Espaço Transcrito Interno 2 (ITS2) têm sido utilizadas em estudos taxonômicos e sua utilidade constatada pela confiabilidade que o método confere à identificação das espécies de Trichogramma. Esta técnica molecular foi bem sucedida em distinguir dezessete espécies nativas e introduzidas de Trichogramma, coletadas na América do Sul. As sequências do DNAr variaram de 379 a 632 pb. Em 11 linhagens de T. pretiosum estudadas, o endosinbionte Wolbachia foi detectado pela primeira vez. Estas linhagens telítocas foram encontradas no Peru (9), Colômbia (1) e Estados Unidos (1). Uma chave dicotômica para identificação de espécies foi construída baseada no tamanho do produto da PCR do ITS2 e em análises de restrição utilizando-se três endonucleases (EcoRI, MseI and MaeI).Palavras-chave: marcadores moleculares, sequências ITS-2, Hymenoptera, parasitóide de ovos.

Phylogeny of the Trichogramma endosymbiont Wolbachia, an alpha-proteobacteria (Rickettsiae)

“…Cytoplasmic incompatibility results in aborted karyogamy (O'Neill and Karr, 1990) and occurs when infected males are crossed with females that are either uninfected (unidirectional incompatibility) (Hoffmann et al, 1986) or infected with another bacterial variant (bidirectional incompatibility); (2) feminization in isopods where genetic males are converted into functional females (Martin et al, 1994;Rousset et al, 1992); (3) the induction of complete parthenogenesis in some haplodiploid species (Almeida and Stouthamer, 2015;Almeida et al, 2010;Stouthamer et al, 1990Stouthamer et al, , 1993. Parthenogenesis-inducing Wolbachia bacteria allow infected female to produce offspring from unfertilized eggs due to a first mitotic division modification (Stouthamer and Kazmer, 1994) and the genetic basis for the loss of female sexual function could be explained by a dominant nuclear effect (Russell and Stouthamer, 2011); (4) fecundity increase of the host for the egg parasitoid Trichogramma bourarachae (Pintureau and Babault, 1980;Vavre et al, 1999b) and (5) male-killing in a wide range of insects.…”

The effects of outbreeding on a parasitoid wasp fixed for infection with a parthenogenesis-inducing Wolbachia symbiont

“…The Insectary line was described previously (Lindsey et al, 2016;Lindsey and Stouthamer, 2017) and exhibits thelytokous parthenogenesis with females hatching from unfertilized eggs as a result of infection with Wolbachia. All Trichogramma pretiosum from Peru that have been tested for Wolbachia are infected and reproduce via thelytokous parthenogenesis (Russell and Stouthamer, 2011;Almeida and Stouthamer, 2015). The Insectary line, while it cannot be converted to a self-sustaining sexual line through antibiotic curing, will fertilize enough eggs to perform introgressions.…”

“…This phenomenon of symbiont-dependence has been documented in some populations of Trichogramma parasitoid wasps. There is extensive inter-and intra-specific variation in Wolbachia infection frequencies across Trichogramma: some populations are never found with Wolbachia (Pinto, 1998), others maintain a consistent low-level infection (Stouthamer and Kazmer, 1994;Stouthamer et al, 2001), and some are completely fixed for Wolbachia-infection (Russell and Stouthamer, 2011;Almeida and Stouthamer, 2015). The extremes of this variation are particularly evident in one species, Trichogramma pretiosum.…”

“…As horizontal transfers become increasingly rare, Wolbachia would become linked to a host genetic background. In contrast to the mixed-infection status and frequent horizontal transfers amongst Trichogramma kaykai, Trichogramma pretiosum is one such species where infection status is often fixed across a region (Pinto, 1998;Almeida and Stouthamer, 2015), and horizontal transfers in the lab have failed (Huigens et al, 2004).…”

Morphogenetic traits of the egg parasitoid Trichogramma for controlling certain date palms lepidopteran insect pests in the New Valley Governorate

“…Therefore, the TNV strain was identified as T. turkestanica. Recently, molecular genetic tools including PCR amplification and the sequencing of the internally transcribed spacer 2 (ITS-2) of the rRNA gene were applied for the accurate identification of many Trichogramma species (Ksentini et al 2010;Sayed et al 2011;Polaszek et al 2012;Pino et al 2013;Nasir et al 2013;Almeida and Stouthamer 2015;Wu et al 2016 andLiu et al 2017).…”