Genetic Diversity of Tamarixia radiata Populations and Their Associated Endosymbiont Wolbachia Species from China

Hafiza Javaria Ashraf,Muhammad Qasim,Bamisope Steve Bamisile,Liande Wang,Wenjie Wang,Komivi Senyo Akutse,Irum Mukhtar,Luis Carlos Ramos Aguila

doi:10.3390/agronomy11102018

Abstract

Tamarixia radiata is one of the established biocontrol pests against the major Asian citrus psyllid, Diaphorina citri, a vector of Candidatus Liberibacter that is a causal agent of citrus Huanglongbing (HLB) disease. Updated information and regional exploration on biocontrol pests are important elements for effective disease management strategies. In this study, the diversity and parasitism rate of T. radiata populations were evaluated. Due to the importance of the host–parasitoid relationship, the presence of Wolbachia as an endosymbiont was also investigated. The parasitism rate of various T. radiata populations from Ecuador and China ranged between 57.27% and 66.32%, respectively, with a non-significant emergence rate and a statistically similar sex ratio. Sequence analysis of ITS and COI from T. radiata populations was consistent with the morphological hypothesis that the collections represent a single species, whereas phylogeny of the wsp gene confirmed the presence of Wolbachia pipientis as an endosymbiont within T. radiata populations. Based on partial COI sequences, the maximum genetic diversity such as total haplotype diversity (Hd = 0.788), nucleotide, diversity (π = 0.2439), and average nucleotide difference (k = 171.844) was also estimated for different T. radiata populations. Furthermore, neutrality tests based on COI sequences indicated an overall contraction in T. radiata populations, whereas an expansion trend was observed in associated W. pipientis strains. This study clearly demonstrated the presence of genetically diverse T. radiata populations that were able to parasitize D. citri effectively, and these can be further explored as promising biocontrol candidates in integrated pest management strategies to solve citriculture economic loss caused by D. citri.

Highlights

Parasitoids constitute a species-rich group containing more than 20% of the world’s insect species [1], divided into six families (Aphelinidae, Encyrtidae, Eulophidae, Eupelmidae, Pteromalidae, and Signiphoridae) within the order Hymenoptera
The obtained sequences of ITS1, ITS2, consisting of the mitochondrial gene (COI), and wsp were blasted in the NCBI database to identify populations of T. radiata and their associated Wolbachia strains
The results showed that different populations of T. radiata were distinguished into two clades of haplotypes (H1–H2)

Summary

Introduction

Parasitoids constitute a species-rich group containing more than 20% of the world’s insect species [1], divided into six families (Aphelinidae, Encyrtidae, Eulophidae, Eupelmidae, Pteromalidae, and Signiphoridae) within the order Hymenoptera. According to the parasitoids’ taxonomic position, Eulophidae contains many species associated with insect hosts [2] These parasitoids use their hosts for nourishment through direct feeding and gradually kill them [3,4]. They effectively reduce their host populations in natural ecosystems and act as biological control agents in the agro-ecosystems. Tamarixia species are parasitoids of psyllids and widely distributed as a classical biological control agent for the management of D. citri in many regions, including Taiwan [5], Reunion Island, Guadeloupe [6] Florida, California, and Texas [7,8,9], due to their high parasitism capability and field adaptation. Due to the adverse effects of insecticides on the fauna and flora, there is a crucial need to introduce an environmentally friendly alternative measure such as biological control agents, natural insect enemies, and entomopathogenic fungi to eradicate D. citri [18,19,20]

Objectives

Methods

Results

Discussion

Conclusion