Symbiotic Fungus Affected the Asian Citrus Psyllid (ACP) Resistance to Imidacloprid and Thiamethoxam.

Tuyong Yi,Ling Lei,Yanyun Hong,Lingguo Li,Ling He,Jianglan Yi,Liangying Dai

doi:10.3389/fmicb.2020.522164

Abstract

The Asian citrus psyllid (ACP), Diaphorina citri (Kuwayama) (Hemiptera: Liviidae), is a notorious Rutaceae plant pest. Frequent and extensive use of pesticides has resulted in severe insecticide resistance in ACP populations. Fully understanding the mechanism of ACP resistance to pesticides is vital for us to control or delay the development of resistance. Therefore, we compared the difference in resistance to imidacloprid and thiamethoxam between Hunan (Yongzhou, Chenzhou) and Guangdong (Guangzhou) ACP populations and analyzed the correlations between the resistance level and genes and symbiotic fungi. The results showed that the resistance of the Guangdong ACP population to imidacloprid and thiamethoxam was lower than that of Hunan ACP population, and the relative expression of genes associated with P450 mono-oxygenase and acetylcholinesterase was significantly lower in the Guangdong ACP population than in Hunan ACP population. The differences of mean relative abundances of four symbiotic bacteria among three populations were marginally significant; however, the mean relative abundance of 16 fungi among three populations was significantly different, and positive linear correlations were observed between the resistance level and two fungi (Aspergillus niger and Aureobasidium pullulans) and two genes (CYP4C70 and CYP4DB1). Negative correlations were only observed between the resistance level and two fungi (Golubevia pallescens and Acremonium sclerotigenum). Moreover, four fungi were unique to the Chenzhou population which was the highest resistance to imidacloprid and thiamethoxam. These findings suggested the P450 mono-oxygenase and symbiotic fungi together affected ACP resistance to imidacloprid and thiamethoxam. In the future, we may use environmental G. pallescens and A. sclerotigenum to control or delay ACP resistance.

Highlights

Chemical control is the most important and widely used measure in controlling most agricultural pests (Dang et al, 2017)
The resistance of the Asian citrus psyllid (ACP) to thiamethoxam and imidacloprid appeared to be significantly different among the three geographical populations based on LC50 and LC95
Regardless of insecticide type, at a given concentration, the ACP population from Guangdong Province has the highest probability of mortality and the lowest resistance to thiamethoxam or imidacloprid

Summary

Introduction

Chemical control is the most important and widely used measure in controlling most agricultural pests (Dang et al, 2017). The analysis of metabolic enzyme activity, application of insecticide synergists, and expression of genes have been used to explore the mechanisms of pesticide resistance. Liu et al (2005) confirmed that nicotinic acetylcholine receptor (nAChR) genes, as targets of neonicotinoid insecticides, affected BPH resistance to imidacloprid. Most studies on insecticide resistance mechanisms have focused on evolutionary changes in pest insect genomes, such as the alteration of pesticide target sites, increase in pesticide excretion rates, and upregulation of ATP binding protein and metabolic enzymes, including general esterase, glutathione S-transferase, and cytochrome P450 mono-oxygenase (Cao et al, 2008; Kikuchi et al, 2012; Wei et al, 2015; Safi et al, 2017; Tian et al, 2018; Wang et al, 2019)

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Results

Conclusion