2 Introduction
The bean bug, Riptortus pedestris (Fabricius) (Hemiptera: Heteroptera) is a notorious pest of soybean crops in Asia (Figure 1A). They obtain nutrients and water by penetrating their sucking mouthpart into leaves, stems, pods, and seeds, leading to significant reductions in seed quality (Bae et al. 2014; Rahman and Lim 2017). Although losses caused by R. pedestris have been mainly reported for leguminous crops, the insects also damage rice, sesame, fruit trees, flowers, and medicinal plants (Bharathimeena and Sudharma 2009; Kang 2003). In recent years, increased attention has been payed to R. pedestris due to its potential roles in causing soybean Zhengqing , which is a staygreen syndrome that has resulted in yield losses from 0 to nearly 100% in the Huang-Huai-Hai River basin in China (Li et al. 2019). In field cage experiments, as well as under laboratory conditions, R. pedestris feeding was found to cause staygreen-like syndromes, with increased numbers of abnormal seeds, more empty pods, a lack of leaf senescence, and decreased yields in infested soybeans (Figure 1B) (Li et al. 2019; Li 2020). Insecticides, such as fenitrothion, bifenthrin, etofenprox, and acetamiprid have been widely used to control R. pedestris (Alim and Lim 2010; Jung et al. 2018). However, the chemical control of R. pedestris is often incompatible with natural enemies and causes pest resurgence, leading to nonnegligible environmental problems.
In addition to causing economic losses, R. pedestris is also an ideal model for investigating symbiotic microbe–insect associations (Takeshita and Kikuchi 2017). Its midgut crypts are filled with numerous environmentally acquired symbionts (Jung and Lee 2019). Among them, the symbiotic Burkholderia , which can be easily cultured and genetically manipulated outside the host, has been best characterized (Ohbayashi et al. 2019; Takeshita and Kikuchi 2017). Different from most insect–microbe symbiotic systems,Burkholderia cannot be vertically transmitted. Instead, they reside within the soil, andR. pedestris orally acquires the symbiont from surrounding environments (Kikuchi et al. 2011). Although Burkholderiasymbionts are not essential for insect survival and R. pedestriscan be reared in aseptic conditions, aposymbiotic insects exhibit retarded growth, smaller body sizes and weights, and lower fecundity (Kikuchi and Fukatsu 2014; Kikuchi et al. 2007). Strikingly, recent findings demonstrated that some insecticide-degradingBurkholderia mediate insecticide resistance in R. pedestris , providing the insects with a potential advantage in insecticide-sprayed crop fields (Itoh et al. 2018; Kikuchi et al. 2012). Currently, the complete genome sequences of several Burkholderiastrains have been reported (Takeshita et al. 2014; Takeshita et al. 2018). It is necessary to unveil the genomic information of their insect hosts as the construction of a high-quality genome can provide new insights into the mechanisms of insect–microbe interactions.
In this study, we report the first genome of a bean bug in Coreoidea with a determined sex chromosome. The genome was de novoassembled using PacBio and Illumina sequencing technology as well as Hi-C technology to assist in chromosome-level assembly. The genomic resource obtained for R. pedestris will benefit further research associated with the insect–microbe interactions, insect–plant interactions, and pesticide resistance of insects, and it provide invaluable information for controlling bug pests.