Abundance and diversity of gut-symbiotic bacteria, the genus Burkholderia in overwintering Riptortus pedestris (Hemiptera: Alydidae) populations and soil in South Korea.

Minhyung Jung,Doo-Hyung Lee,Maohua Chen

doi:10.1371/journal.pone.0218240

Abstract

Riptortus pedestris is a major agricultural pest on leguminous plants in South Korea and Japan. Recent studies have revealed that R. pedestris can form beneficial symbiosis with bacteria belonging to genus Burkholderia acquired from soil newly for every generation. Although their physiological interactions are relatively well-understood, infection rate and abundance of the Burkholderia in overwintering natural populations of R. pedestris remain unknown. Therefore, the objective of this study was to characterize Burkholderia infection ratio and clade composition of overwintering R. pedestris populations as well as prevalence and diversity of the genus Burkholderia in soil by conducting a two-year field survey. From the field survey, we found 29 overwintering R. pedestris adults in forested areas nearby soybean fields. Diagnostic PCR analysis revealed that overall infection rate of the symbiotic Burkholderia was 93.1% from overwintering adults. Among the Burkholderia-infected R. pedestris, 70.4% of individuals harbored unclassified Burkholderia clades whereas 22.2% and 7.4% of R. pedestris harbor stinkbug-associated beneficial and environmental (SBE) group and Burkholderia cepacia and complex (BCC), respectively. All R. pedestris were infected with a single clade of Burkholderia. In soil, 56.2% of soil samples were Burkholderia positive, and unlike R. pedestris, multiple Burkholderia clades were detected from 62.2% of those samples. Clade composition of the genus Burkholderia in the samples with the bacteria was 91.1%, 60.0%, 31.1% and 8.8% for plant-associated beneficial and environment (PBE), BCC, SBE and unclassified clade, respectively.

Highlights

During winter season, insects face thermally stressful environments
The greatest number of overwintering R. pedestris was found in Paju and Muan over two years
Infection rate and clade composition of symbiotic Burkholderia in R. pedestris field populations provides critical information to better design and implement pest management programs against this economically-important pest. It is currently unknown how symbionts affect the biology of overwintering R. pedestris, it is expected that higher infection rates in overwintering populations would impose higher risk to crops by survived pests in the spring

Summary

Introduction

They have developed various strategies to successfully withstand and survive inhospitable environments through evolutionary interactions with organisms and abiotic conditions [1,2]. Their physiological strategies for cold hardness can be classified into two groups: freeze tolerant (synthesis of ice nucleating agents) and freeze avoidance (removal of all potential nucleates) [2,3,4,5]. Understanding overwintering ecology is important for pest species because levels of survived winter populations can serve as a barometer for estimating pest pressures in succeeding active seasons [1,3,4]. The timing and size of spring emerge populations have been forecasted for aphid management by evaluating overwintering eggs of black bean aphid, Aphis fabae Scolpoli (Hemiptera: Aphididae) [1,8,9] and cereal aphid, Rhopalosiphum padi Linnaeus (Hemiptera: Aphididae) [10]

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