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BackgroundMicrobial communities that inhabit the mosquito body play an import role in host biology and may have potential for mosquito control. However, the forces that shape these microbial communities are poorly understood.MethodsTo gain a better understanding of how host location influences the composition and diversity of mosquito microbiota, we performed a survey of microbial communities in mosquito samples collected from six USA states using HiSeq sequencing of the 16S rRNA gene.ResultsA total of 284 bacterial operational taxonomic units (OTUs) belonging to 14 phyla were detected in nine mosquito species, with Proteobacteria, Firmicutes and Actinobacteria accounting for 95% of total sequences. OTU richness varied markedly within and between mosquito species. The microbial composition and diversity was heavily influenced by the site of mosquito collection, suggesting that host location plays an important role in shaping the mosquito microbiota.ConclusionsVariation in microbial composition and diversity between mosquitoes from different locations may have important implications on vector competence and transmission dynamics of mosquito-borne pathogens. Future studies should investigate the environmental factors responsible for these variations and the role of key bacteria characterized in this study on mosquito biology and their potential application in symbiotic control of mosquito-borne diseases.Electronic supplementary materialThe online version of this article (10.1186/s13071-018-3036-9) contains supplementary material, which is available to authorized users.

Soybean thrips (Neohydatothrips variabilis) are one of the most efficient vectors of soybean vein necrosis virus, which can cause severe necrotic symptoms in sensitive soybean plants. To determine which other viruses are associated with soybean thrips, the metatranscriptome of soybean thrips, collected by the Midwest Suction Trap Network during 2018, was analyzed. Contigs assembled from the data revealed a remarkable diversity of virus-like sequences. Of the 181 virus-like sequences identified, 155 were novel and associated primarily with taxa of arthropod-infecting viruses, but sequences similar to plant and fungus-infecting viruses were also identified. The novel viruses were predicted to have positive-sense RNA, negative-stranded RNA, double-stranded RNA, and single-stranded DNA genomes. The assembled sequences included 100 contigs that represented at least 95% coverage of a virus genome or genome segment. Sequences represented 12 previously described arthropod viruses including eight viruses reported from Hubei Province in China, and 12 plant virus sequences of which six have been previously described. The presence of diverse populations of plant viruses within soybean thrips suggests they feed on and acquire viruses from multiple host plant species that could be transmitted to soybean. Assessment of the virome of soybean thrips provides, for the first time, information on the diversity of viruses present in thrips.

With the discovery of the soybean aphid (Aphis glycinesMatsumura) as a devastating insect pest of soybean (Glycine max(L.) Merr.) in the United States, host resistance was recognized as an important management option. However, the identification of soybean aphid isolates exhibiting strong virulence against aphid resistance genes (Raggenes) has highlighted the need for pyramiding genes to help ensure the durability of host resistance as a control strategy. In this study, soybean isolines with all possible combinations of the resistance and susceptibility alleles atRag1, Rag2, and Rag3were evaluated for their effectiveness against the four characterized soybean aphid biotypes. All soybean isolines, including the susceptible check carrying none of the resistance alleles (S1/S2/S3), were infested with each biotype in no-choice greenhouse tests, and the aphid populations developed on each isoline were enumerated 14 d after infestation. All gene combinations, with the exception ofRag3alone, provided excellent protection against biotype 1. Isolines withRag2alone or in combination withRag1andRag3had greater levels of resistance to biotype 2 than those with eitherRag1alone,Rag3alone, or theRag1/3pyramid. For biotype 3, theRag1/3andRag1/2/3pyramided lines significantly reduced aphid populations compared with all other gene combinations, while theRag1/2/3pyramid provided the greatest protection against biotype 4. Overall, theRag1/2/3pyramided line conferred the greatest protection against all four biotypes.

Inadequate plant nutrition and biotic stress are key threats to current and future crop yields. Zinc (Zn) deficiency and toxicity in major crop plants have been documented, but there is limited information on how pathogen and pest damage may be affected by differing plant Zn levels. In our study, we used soybean plants as a host, a soybean pest, and three soybean pathogens to determine whether plant Zn levels change pest and disease assessments. Two soybean cultivars were grown in sand culture with a soluble nutrient solution that ranged from Zn-deficient to toxic. Detached leaves from these plants were either inoculated with Aphis glycines, the soybean aphid, Xanthomonas axonopodis pv. glycines, a bacterium that causes bacterial pustule, Sclerotinia sclerotiorum, the necrotrophic fungus responsible for stem rot, or Phakopsora pachyrhizi, a biotrophic obligate pathogen that causes soybean rust. There were significant (P < 5%) effects on aphid colonization, positive counts for bacterial pustule, S. sclerotiorum leaf area affected, and numbers of rust lesions associated with the Zn treatments. Plants grown with the physiologically optimal levels of Zn (2 μM) had less (P < 5%) soybean aphids cm -2 leaflet than plants grown without Zn, at 0.1 Zn (0.2 μM), or at 100 Zn fertilization (200 μM). Plants grown with the normal fertilization of Zn or 100 Zn had fewer (P < 5%) positive counts for bacterial pustule and less lesion area affected by S. sclerotiorum than plants grown without Zn or fertilized with 0.1 Zn. For soybean rust, plants grown with the physiologically optimal fertilization of Zn or 100 Zn had higher (P < 5%) lesions cm -2 on leaflets from plants grown without Zn or fertilized with 0.1 Zn. These results indicate different Zn nutrition levels in soybean significantly affected aphid and disease development.

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Global temperatures are generally increasing, and this is leading to a well documented advancement and extension of seasonal activity of many pest insects. Effects of changing precipitation have received less attention, but might be complex because rain and snow are increasing in some places but decreasing in others. This raises the possibility that altered precipitation could accentuate, or even reverse, the effects of rising temperatures on pest outbreaks. We used >592 K aphid suction-trap captures over 15 years, in the heavily farmed central USA, to examine how the activity of Aphis glycines (soybean aphid), Rhopalosiphum maidis (corn aphid), and Rhopalosiphum padi (bird cherry-oat aphid) changed with variation in both temperature and precipitation. Increasing precipitation caused late-season flight activity of A. glycines and early-season activity of R. padi to shift earlier, while increasing temperature did the same for early-season activity of A. glycines and R. maidis.In these cases, precipitation and temperature exhibited directionally similar, but independent, effects. However, precipitation sometimes mediated temperature effects in complex ways. At relatively low temperatures, greater precipitation generally caused late-season flights of R. maidis to occur earlier. However, this pattern was reversed at higher temperatures with precipitation delaying late-season activity. In contrast, greater precipitation delayed peak flights of R. padi at lower temperatures, but caused them to occur earlier at higher temperatures. So, in these two cases the interactive effects of precipitation on temperature were mirror images of one another. When projecting future aphid flight phenology, models that excluded precipitation covariates consistently underpredicted the degree of phenological advance for A. glycines and R. padi, and underpredicted the degree of phenological delay for R. maidis under expected future climates. Overall, we found broad evidence that changing patterns of aphid flight phenology could only be understood by considering both temperature and precipitation changes. In our study region, temperature and precipitation are expected to increase in tandem, but these correlations will be reversed elsewhere. This reinforces the need to include both main and