Common facultative endosymbionts do not influence sensitivity of cereal aphids to pyrethroids

Abstract

1. Cereal aphids, including the bird cherry-oat aphid, Rhopalosiphum padi, and the grain aphid, Sitobion avenae, can transmit viruses that significantly reduce crop yields. To mitigate against yield losses, insecticides are routinely used to manage aphid populations.2. Aphids can form relationships with endosymbionts that confer fitness benefits or consequences to the aphid. Recent artificial inoculation experiments indicate that endosymbionts could increase aphid susceptibility to insecticides, but this has not been explored using aphid populations naturally infected with endosymbionts.3. Here, we sampled aphids from an important cereal production region in Lower Saxony, Germany. We characterised the endosymbiont profile of these aphid populations and conducted pyrethroid dose-response assays to test the hypothesis that facultative endosymbionts increase aphid susceptibility to insecticides.4. We find that the level of insecticide susceptibility is highly variable in S. avenae and we identify populations that are sensitive and tolerant to pyrethroids, including populations collected from the same field. For R. padi, we find evidence for decreased sensitivity to pyrethroids, representing the first report of reduced sensitivity to pyrethroids in R. padi sampled from Central Europe.5. We detected high endosymbiont infection frequencies in the aphid populations. 84% of aphids carry one facultative endosymbiont and 9% of aphids carry two facultative endosymbionts. We detected associations with Regiella insecticola, Fukatsia symbiotica, and Hamiltonella defensa. However, we do not identify a link between endosymbiont infection and insecticide susceptibility, indicating that other factors may govern the development of insecticide resistance and the need for alternative management strategies..

How does vector diversity influence the transmission efficiency of yellow dwarf virus? Perspectives from a review

“…Multiple facultative endosymbionts have been described to associate with aphids, and eight of these endosymbiont species have been detected in cereal aphids: Fukatsuia symbiotica , Hamiltonella defensa , Regiella insecticola , Rickettsia spp., Ricketsiella spp., Aresnophonus spp., Serratia symbiotica and Spiroplasma spp. (Guo et al., 2019; Leybourne et al., 2023; Leybourne, Bos, et al., 2020; Zytynska et al., 2023). In cereal aphids these endosymbionts can occur individually or co‐occur alongside other endosymbionts in a range of multi‐infections (Leybourne et al., 2023; Zytynska et al., 2023).…”

“…Rickettsia spp., Ricketsiella spp., Aresnophonus spp., Serratia symbiotica and Spiroplasma spp. (Guo et al, 2019;Leybourne et al, 2023;Zytynska et al, 2023). In cereal aphids these endosymbionts can occur individually or co-occur alongside other endosymbionts in a range of multi-infections (Leybourne et al, 2023;Zytynska et al, 2023).…”

“…(Guo et al., 2019; Leybourne et al., 2023; Leybourne, Bos, et al., 2020; Zytynska et al., 2023). In cereal aphids these endosymbionts can occur individually or co‐occur alongside other endosymbionts in a range of multi‐infections (Leybourne et al., 2023; Zytynska et al., 2023). Infection frequencies of these nonessential endosymbionts are highly variable and generally range from 0% to 80%, depending on the endosymbiont and aphid species (Guo et al., 2019; Henry et al., 2015; Leybourne et al., 2023; Leybourne, Bos, et al., 2020; Zytynska et al., 2023).…”

A diversity of endosymbionts across Australian aphids and their persistence in aphid cultures

“…Perhaps there is a connection between the more limited chemical control (with a smaller range of pesticides applied) in urban areas compared with agricultural areas. Some studies have linked symbionts to pesticide resistance, including connections to imidacloprid susceptibility in A. gossypii (Guo et al, 2020), although in other aphids there is no link between endosymbiont profiles and pyrethroid susceptibility (Leybourne et al, 2023). Some endosymbionts contribute to resistance against pesticides by degrading toxins (Itoh et al, 2018).…”

Secondary symbionts affect aphid fitness and the titer of primary symbiont

“…Aphids display relationships with symbionts that confer fitness benefits or costs to themselves ( Leybourne et al., 2022 ). H. defensa has been well-studied in Acyrthosiphon pisum (Harris) ( McLean and Godfray, 2015 ), illustrating S-symbiont could confer aphid protection against parasitoids while imposing life-history costs ( Cayetano et al., 2015 ) and may exhibit a detrimental effect on aphid fitness with a 60% fecundity reduction on average ( Simon et al., 2011 ).…”