Soybean Aphid Research Articles

Discovery of Known and Novel Viral Genomes in Soybean Aphid by Deep Sequencing

The phytobiome includes not just cellular microorganisms, but also all viruses associated with plants: the virome. Plants and aphids exchange viruses regularly and efficiently; thus, the plant virome is tightly linked with the aphid virome. Yet, little is known about aphid viromes, particularly that of the soybean aphid (Aphis glycines), one of the most economically important pest insects of soybean. To sample the soybean aphid virome, and to seek new viruses as potential biological control agents, we employed next-generation sequencing. Genomes isolated from viruses in soybean aphids collected at four sites revealed many viruses, and six complete or nearly complete genomes were assembled. Most abundant were the picornavirus-like dicistroviruses Aphid lethal paralysis virus and Rhopalosiphum padi virus. We also sequenced the genome of a new dicistrovirus, Big Sioux River virus, fragments of which had been found previously in honey bee. Genome sequences that represent two entirely new virus families were obtained. These include an abundant tetravirus-like virus and a virus distantly related to cileviruses of plants and negeviruses of insects. Surprisingly, Cotton leafroll dwarf virus, a member of the genus Polerovirus, was found in soybean aphids from China, suggesting that the soybean aphid may be a vector of this virus. This virus had not been reported previously in China or in soybean. This study provides a peek into the rapidly expanding, largely unexplored world of insect viromes that will provide valuable knowledge for future understanding of plant−virus−vector interactions. [Formula: see text] Copyright © 2017 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Laboratory Evaluation of Soybean Plant Introductions for Resistance toAphis glycines(Hemiptera: Aphididae)1

The soybean aphid (SA), Aphis glycines Matsumura, is a major pest of soybean in the north-central United States and south-central Canada. It is controlled primarily with insecticides, but the development of aphid-resistant soybean cultivars may provide an alternative management tactic. The viability of this management tactic depends on a diverse set of resistance sources in order to counter various resistance-breaking biotypes of SA, and the identification of new sources of resistance necessitates additional testing of soybean germplasm. The current study used no-choice tests to identify SA resistance in seven early maturing (maturity group I) soybean plant introductions (PIs) that had been advanced from free-choice screening trials. The tests showed PI 437353 and PI 612759 C had an intermediate level of resistance against avirulent SA, whereas PI 437282, PI 437658, PI 437733, PI 548417, and PI 548530 exhibited no significant resistance. Additional research is needed to determine if the source of resistance in PI 437353 and PI 612759 C is due to novel resistant genes, which would help diversify resistance to SA in soybean. Screening and follow-up tests of additional soybean germplasm is warranted in order to ensure the development of durable, SA-resistant cultivars.

Identification and Counting of Soybean Aphids from Digital Images Using Shape Classification

Abstract. Soybean aphids are serious pests, causing negative yield impacts in the crop. Assessing their population is essential for making appropriate pesticide application decisions. Manual identification and counting, which is commonly performed to determine the economic threshold level, is time-consuming, laborious, and causes visual fatigue. In this study, an automatic image processing method was developed to identify and count aphids as well as exoskeletons and leaf spots on soybean leaves based on shape analysis. Aphid-infested soybean trifoliates were obtained at three infestation rates (low, medium, and high). Images of the front sides of the leaves were captured in the laboratory with three cameras (digital single-lens reflex or DSLR, consumer-grade digital, and smartphone) under two lighting conditions (direct and indirect). The shape parameters considered were area, perimeter, convex area, eccentricity, aspect ratio, solidity, hollowness, and roundness. Among the shape parameters tested, hollowness was the best in identifying aphids and was therefore used for developing the object classification algorithm. Of the three cameras tested, images from the consumer-grade digital camera produced the best identification accuracy (>82.4%), followed by the DSLR camera (>81.2%) and smartphone camera (>37.9%). Statistical analysis revealed that the accuracies did not differ significantly under different lighting conditions (p = 0.43), but the accuracies differed for the smartphone camera compared to the DSLR and consumer-grade digital cameras (p = 8.87 × 10-10). The results of automatic and manual counting were very well correlated (r = 0.92). The automatic image processing method achieved more rapid counting (<2 s per image after loading the image) compared to manual counting (~5 min per image). The developed approach for aphid identification and counting can be easily applied to other pest identification issues with minor modifications to the algorithm. Keywords: Aphids, Classification, Image processing, Segmentation, Shape analysis, Soybean.

Monitoring Bean pod mottle virus and Soybean mosaic virus Incidence at Different Soybean Growth Stages in Alabama

This study focuses on Bean pod mottle virus (BPMV) and Soybean mosaic virus (SMV) incidence over time relative to stages of plant growth in selected fields in Alabama. Five commercial soybean fields in west-central Alabama were surveyed for BPMV and SMV in 2010-2012 and 2014. Incidence of BPMV was typically highest at crop maturity. Incidence of 10% or higher was recorded at full bloom in at least one field in each year of the study, but incidence did not exceed 23% at bloom in any field with one exception. SMV was not detected at high levels during this study and incidence above 10% at full bloom was recorded for only one field. Results from this study, combined with observations from a previous statewide survey, indicate that BPMV is the most common virus disease of soybeans in Alabama. BPMV has the potential to cause yield loss in years when bean leaf beetles, its most important vector, are present at high levels early in the season when infection of soybean prior to flowering is possible. Results also suggest that SMV incidence in soybean in Alabama is low in most years and the disease might not pose a significant threat to soybean production at this time, especially in the absence of high populations of soybean aphids in the state.

Soybean Aphid Efficacy Screening Program, 2016*

Soybean Aphid Efficacy Screening Program, 2016*

Resistance to Soybean Aphid in Early-Maturing Plant Introductions of Soybean, 2012–2015

Resistance to Soybean Aphid in Early-Maturing Plant Introductions of Soybean, 2012–2015

The Effect of Temperature and Host Plant Resistance on Population Growth of the Soybean Aphid Biotype 1 (Hemiptera: Aphididae).

A laboratory experiment was conducted to evaluate direct and indirect effects of temperature on demographic traits and population growth of biotype 1 of the soybean aphid, Aphis glycines Matsumura. Our objectives were to better understand how temperature influences the expression of host plant resistance, quantify the individual and interactive effects of plant resistance and temperature on soybean aphid population growth, and generate thermal constants for predicting temperature-dependent development on both susceptible and resistant soybeans. To assess indirect (plant-mediated) effects, soybean aphids were reared under a range of temperatures (15-30 °C) on soybean seedlings from a line expressing a Rag1 gene for resistance, and life history traits were quantified and compared to those obtained for soybean aphids on a susceptible soybean line. Direct effects of temperature were obtained by comparing relative differences in the magnitude of life-history traits among temperatures on susceptible soybeans. We predicted that temperature and host plant resistance would have a combined, but asymmetrical, effect on soybean aphid fitness and population growth. Results showed that temperature and plant resistance influenced preimaginal development and survival, progeny produced, and adult longevity. There also appeared to be a complex interaction between temperature and plant resistance for survival and developmental rate. Evidence suggested that the level of plant resistance increased at higher, but not lower, temperature. Soybean aphids required about the same number of degree-days to develop on resistant and susceptible plants. Our results will be useful for making predictions of soybean aphid population growth on resistant plants under different seasonal temperatures.

Establishment of in vitro soybean aphids, Aphis glycines (Hemiptera: Aphididae): a tool to facilitate studies of aphid symbionts, plant-insect interactions and insecticide efficacy.

Studies on plant-insect interactions of the soybean aphid, Aphis glycines (Matsumura), can be influenced by environmental fluctuations, status of the host plant and variability in microbial populations. Maintenance of aphids on in vitro-grown plants minimizes environmental fluctuations, provides uniform host materials and permits the selective elimination of aphid-associated microbes for more standardized controls in aphid research. Aphids were reared on sterile, in vitro-grown soybean seedlings germinated on plant tissue culture media amended with a mixture of antimicrobials. For initiation and maintenance of in vitro aphid colonies, single aphids were inoculated onto single in vitro seedlings. After three rounds of transfer of 'clean' aphids to fresh in vitro seedlings, contamination was no longer observed, and aphids performed equally well when compared with those reared on detached leaves. The addition of the insecticides thiamethoxam and chlorantraniliprole to the culture medium confirmed uptake and caused significant mortality to the in vitro aphids. The use of the antimicrobial mixture removed the associated bacteria Arsenophonus but retained Buchnera and Wolbachia within the in vitro aphids. The in vitro aphid system is a novel and highly useful tool to understand insecticidal efficacy and expand our knowledge of tritrophic interactions among plants, insects and symbionts. © 2016 Society of Chemical Industry.

Detection of soybean aphids in a greenhouse using an image processing technique

Soybean aphid (Aphis glycines) is one of the most important insect pests of soybeans in North America. Insecticide application is performed if the aphids count exceeds the economic threshold of 250 per plant. Precise estimates of aphid densities are needed for field conditions to maximize insecticide application efficiency. The current method of identifying and counting aphids on a plant is a labor-intensive and time consuming process. The objective of this study was to use image processing technique to detect and count different sized soybean aphids on a soybean leaf. The trials were conducted with soybean plants grown in a greenhouse. Three sets of data were collected on different dates using replicate plants from 4 soybean varieties infested with a range of aphid densities. Images of infested soybean trifoliate leaves were captured with different cameras under 2 different illumination conditions with different cameras used across the different data sets. The images captured were processed in MATLAB™ R2014a software using the Image Processing Toolbox to identify and count aphids. In order to evaluate the accuracy of the algorithm, the aphids counted with the sensing system were compared to a count generated manually by a trained expert. The algorithm counting with SONY™ camera images correlated (r2=0.96) very well with manual counts. The misclassification percentage was low for most cameras with different resolutions under high illumination conditions. The results also showed that images captured with an inexpensive regular digital camera gave satisfactory results under high illumination conditions.

Tolerance of KS-4202 Soybean to the Attack ofBemisia tabaciBiotype B (Hemiptera: Aleyrodidae)

Abstract Bemisia tabaci (Gennadius) biotype B (Hemiptera: Aleyrodidae) is considered one of the most important pests of soybean, Glycine max L. (Merrill) (Fabaceae), in Brazil and worldwide. Although chemical control still represents the principal strategy used to control this insect, less aggressive strategies such as the use of resistant genotypes stand out as potentially efficient alternatives for integrated pest management programs. This study aimed to evaluate the possible occurrence of tolerance to B. tabaci biotype B in the ‘KS-4202’ soybean genotype, which is already recognized as tolerant to Aphis glycines Matsumura (Hemiptera: Aphididae) in the United States. The ‘Conquista’ Brazilian cultivar was used as a susceptible control. In a greenhouse, plants (stages V3–V4) of both genotypes were individualized and subjected to 6 patterns of infestation: 1) uninfested and without chemical control; 2) infested and without chemical control; 3) infested and sprayed at 15 d after infestation (DAI); 4) infes...

Explicit modeling of abiotic and landscape factors reveals precipitation and forests associated with aphid abundance.

Increases in natural or noncrop habitat surrounding agricultural fields have been shown to be correlated with declines in insect crop pests. However, these patterns are highly variable across studies suggesting other important factors, such as abiotic drivers, which are rarely included in landscape models, may also contribute to variability in insect population abundance. The objective of this study was to explicitly account for the contribution of temperature and precipitation, in addition to landscape composition, on the abundance of a widespread insect crop pest, the soybean aphid (Aphis glycines Matsumura), in Wisconsin soybean fields. We hypothesized that higher soybean aphid abundance would be associated with higher heat accumulation (e.g., growing degree days) and increasing noncrop habitat in the surrounding landscape, due to the presence of the overwintering primary hosts of soybean aphid. To evaluate these hypotheses, we used an ecoinformatics approach that relied on a large dataset collected across Wisconsin over a 9-year period (2003-2011), for an average of 235 sites per year (n=2,110 fields total). We determined surrounding landscape composition (1.5-km radius) using publicly available satellite-derived land cover imagery and interpolated daily temperature and precipitation information from the National Weather Service COOP weather station network. We constructed linear mixed models for soybean aphid abundance based on abiotic and landscape explanatory variables and applied model averaging for prediction using an information theoretic framework. Over this broad spatial and temporal extent in Wisconsin, we found that variation in growing season precipitation was positively related to soybean aphid abundance, while higher precipitation during the nongrowing season had a negative effect on aphid populations. Additionally, we found that aphid populations were higher in areas with proportionally more forest but were lower in areas where minor crops, such as small grains, were more prevalent. Thus, our findings support our hypothesis that including abiotic drivers increases our understanding of crop pest abundance and distribution. Moreover, by explicitly modeling abiotic factors, we may be able to explore how variable climate in tandem with land cover patterns may affect current and future insect populations, with potentially critical implications for crop yields and agricultural food webs.

Aphis Glycines Virus 2, a Novel Insect Virus with a Unique Genome Structure.

The invasive soybean aphid, Aphis glycines, is a major pest in soybeans, resulting in substantial economic loss. We analyzed the A. glycines transcriptome to identify sequences derived from viruses of A. glycines. We identified sequences derived from a novel virus named Aphis glycines virus 2 (ApGlV2). The assembled virus genome sequence was confirmed by reverse transcription polymerase chain reaction (RT-PCR) and Sanger sequencing, conserved domains were characterized, and distribution, and transmission examined. This virus has a positive sense, single-stranded RNA genome of ~4850 nt that encodes three proteins. The RNA-dependent RNA polymerase (RdRp) of ApGlV2 is a permuted RdRp similar to those of some tetraviruses, while the capsid protein is structurally similar to the capsid proteins of plant sobemoviruses. ApGlV2 also encodes a larger minor capsid protein, which is translated by a readthrough mechanism. ApGlV2 appears to be widespread in A. glycines populations and to persistently infect aphids with a 100% vertical transmission rate. ApGlV2 is susceptible to the antiviral RNA interference (RNAi) pathway. This virus, with its unique genome structure with both plant- and insect-virus characteristics, is of particular interest from an evolutionary standpoint.

Beyond Focal Pests: Impact of a Neonicotinoid Seed Treatment and Resistant Soybean Lines on a Non-Target Arthropod.

Integrated pest management (IPM) tactics may effectively control focal pests, but it is also important to test the compatibility of different tactics, and consider non-target organisms. We investigated the effects of a neonicotinoid seed treatment and Rag resistance genes used for soybean aphid (Aphis glycines Matsumura) control on reproduction of a non-target herbivore (twospotted spider mite, Tetranychus urticae Koch) in short-term greenhouse experiments. We also examined interactions between spider mites and a specialist phytoseiid mite [Ambylseius fallacis (Garman)] and assessed the effects of a co-occurring opportunistic omnivore [Frankliniella occidentalis (Pergande)] by including thrips density as a covariate. There were no interactive or main effects of the presence of Rag genes on the densities of any of the arthropods. Overall, effects of the seed treatment on spider mite densities varied, with no difference when mites were confined in clip cages, and higher populations on seed-treated plants when on whole plants. Predatory mites had a consistent negative impact on spider mites, and densities of A. fallacis immatures were similar between seed treated and non-seed treated plants. However, the relationship between spider mite and thrips densities was different between these two plant types, but only in the clip cage experiment lacking predatory mites. This research highlights the importance of considering how IPM tactics might affect non-target organisms.

Evaluation of Aphis glycines as an Alternative Host for Supporting Aphelinus albipodus Against Myzus persicae on Capsicum annuum cv. Ox Horn and Hejiao 13.

Bank plant systems provide effective biological control for pests infesting commercially important crops. Aphids cause physical damage to crops by feeding on the leaves, as well as transmitting damaging viral diseases. To develop a bank plant system to control aphids that damage vegetable crops, we initially reared the parasitoid Aphelinus albipodus (Hayat and Fatima) on the soybean aphid, Aphis glycines (Matsumura) reared on the soybean plant, Glycine max (L.) that was elected as the alternate host. Parasitoid adults that emerged from A. glycines were allowed to parasitize second instar nymphs of the aphid Myzus persicae (Sulzer) which were reared on sweet pepper and chili pepper leaves. The results showed that A. albipodus females feeding and parasitizing M. persicae nymphs reared on sweet pepper lived for 18.9days, with an average fecundity of 337.3 progenies/female, while females feeding and parasitizing on M. persicae nymphs reared on chili pepper lived for 18.8days, with an average fecundity of 356.2 progenies/female. There were no significant difference in the development time and reproduction of A. albipodus individuals parasitizing M. persicae nymphs reared on sweet pepper and chili pepper plants. The intrinsic rate of increase (r), net reproductive rate (R 0), net aphid killing rate (Z 0), and finite aphid killing rate (θ) of A. albipodus parasitizing sweet pepper and chili pepper M. persicae was 0.2258days-1, 171.7 progeny adults, 222.6 aphids, and 0.4048 and 0.2295days-1, 191.8 progeny adults, 243.3 aphids, and 0.4021, respectively. Our results suggested that A. glycines could serve as an effective alternative host for supporting A. albipodus against M. persicae infesting sweet pepper and chili pepper.

Overexpression of Nictaba-Like Lectin Genes from Glycine max Confers Tolerance toward Pseudomonas syringae Infection, Aphid Infestation and Salt Stress in Transgenic Arabidopsis Plants.

Plants have evolved a sophisticated immune system that allows them to recognize invading pathogens by specialized receptors. Carbohydrate-binding proteins or lectins are part of this immune system and especially the lectins that reside in the nucleocytoplasmic compartment are known to be implicated in biotic and abiotic stress responses. The class of Nictaba-like lectins (NLL) groups all proteins with homology to the tobacco (Nicotiana tabacum) lectin, known as a stress-inducible lectin. Here we focus on two Nictaba homologs from soybean (Glycine max), referred to as GmNLL1 and GmNLL2. Confocal laser scanning microscopy of fusion constructs with the green fluorescent protein either transiently expressed in Nicotiana benthamiana leaves or stably transformed in tobacco BY-2 suspension cells revealed a nucleocytoplasmic localization for the GmNLLs under study. RT-qPCR analysis of the transcript levels for the Nictaba-like lectins in soybean demonstrated that the genes are expressed in several tissues throughout the development of the plant. Furthermore, it was shown that salt treatment, Phytophthora sojae infection and Aphis glycines infestation trigger the expression of particular NLL genes. Stress experiments with Arabidopsis lines overexpressing the NLLs from soybean yielded an enhanced tolerance of the plant toward bacterial infection (Pseudomonas syringae), insect infestation (Myzus persicae) and salinity. Our data showed a better performance of the transgenic lines compared to wild type plants, indicating that the NLLs from soybean are implicated in the stress response. These data can help to further elucidate the physiological importance of the Nictaba-like lectins from soybean, which can ultimately lead to the design of crop plants with a better tolerance to changing environmental conditions.

Population genetics of the soybean aphid in North America and East Asia: test for introduction between native and introduced populations

Understanding the population genetic diversity and structure of recently introduced pest species is important for determining appropriate strategies for pest control. In recent years, the rate of introduction of new invasive insect pests between continents has continued to increase. About a decade ago, the soybean aphid, Aphis glycines Matsumura, was introduced from East Asia (EA) into North America (NA) and is now widely established in NA. To compare soybean aphid populations between the native and invasive regions, we examined 689 individuals obtained from 28 different collections in NA and EA. A total of 8 microsatellite loci were used for population genetics statistics. Genetic differentiations among NA populations were very low compared to those among EA populations. Gene diversity and mean number of alleles in NA populations averaged 0.40 and 2.70, respectively, whereas in EA they averaged 0.55 and 4.32, respectively. Structure analysis of all populations revealed two distinct structures in the invaded and in the native regions. NA populations were divided into two distinct structures consistent with their geographic distribution. Among EA populations, certain Korean populations were genetically closest to NA populations, especially those from Ohio and Delaware. An approximate Bayesian computation test also supports an introduction into NA from Korea. These suggest that Korea is most likely to be the origin of soybean aphids in North America, rather than China or Japan.

Evaluating Categories of Resistance in Soybean Genotypes from the United States and Brazil toAphis glycines(Hemiptera: Aphididae)

Abstract Aphis glycines Matsumura (Hemiptera: Aphididae), the soybean aphid, has become an important pest of soybeans, leading to significant yield losses in the United States. Host plant resistance is a viable alternative for managing A. glycines. The objectives of this study were to identify and categorize sources of resistance in soybean to A. glycines on genotypes from the United States and Brazil. An antixenosis assay was initially conducted with 8 genotypes to evaluate attractiveness to A. glycines. The selected soybean genotypes were further evaluated in a colonization assay to investigate the resistance of the genotypes at V1 (fully developed leaves at unifoliate node, 1st trifoliate leaf unrolled) and V3 (fully developed leaf at 2nd trifoliate node, 3rd trifoliate leaf unrolled) stages. An antibiosis assay was also conducted, in which multiple biological parameters of A. glycines were recorded. In the antixenosis assay, PI 200538, IAC 24, and IAC 17 genotypes were least attractive to adults of A....

Design, Synthesis, and Bioassay of Novel Compounds of Isolongifolenone Oxime Derivatives

A succession of new isolongifolenone oxime derivatives have been designed and synthesized. The structures of these compounds were identified by IR, 1H‐NMR, 13C‐NMR, mass spectra, and elemental analysis. The bioassays of antibacterial, antifungal, and insecticidal activity were carried out. The in vitro antibacterial and antifungal activities were evaluated by the disk diffusion method, and the minimum inhibitory concentration was determined by the microdilution method, while the insecticidal activity was tested by the spraying method or the straw impregnation method. The results of bioassays showed that compound 3f was more active in resisting all the tested bacterial and fungal organisms when compared to the standard drug amoxicillin at the lowest concentration of 31.3 μg/ml. Compound 4, synthesized by Beckmann rearrangement reaction of isolongifone oxime, exerted moderate insecticidal activity against soybean aphid. Furthermore, compound 3m exhibited more activity in killing armyworms than the standard drug flucycloxuron at the concentration of 0.5 mg/l.

Workplace Harassment: The influence of corporate psychopathy and the HEXACO model of personality

Bamboo tar is a water-insoluble semi-solid waste generated from bamboo charcoal processing, and its increasing accumulation threatens environment and sustainability of the charcoal industry that enhances the economic value of bamboo forestry in southern China. Here we converted bamboo tar to a completely water-soluble sodium salt through full alkalization with NaOH and evaluated its insecticidal activity against the cotton aphid Aphis gossypii, the soybean aphid Aphis glycines and the green peach aphid Myzus persicae in laboratory bioassays and field trials. The tar salt LC50s against the three global aphid pests decreased to 35–93 μg/ml on day 7 from 246 to 486 μg/ml on day 3. In three field trials, the tar salt at the application rates of 338–675 g/ha controlled the aphid pests as efficaciously as but more persistently than pymetrozine (a synthetic aphidicide) at the recommended rate. Our results highlight an easy approach to converting bamboo tar to a promising botanical aphidicide but extensive further work to determine its toxicity and environmental and crop safety is needed.

Potential for Sulfoxaflor to Improve Conservation Biological Control of Aphis glycines (Hemiptera: Aphididae) in Soybean.

Soybean aphid, Aphis glycines Matsumura, is one of the most important insect pests of soybean in the north central United States. Management of A. glycines currently relies on applications of broad-spectrum insecticides. However, broad-spectrum insecticides can negatively impact the natural enemies associated with aphids. Selective insecticides, on the other hand, are promising control tactics for reducing the negative impact of insecticide applications. Here, we compared the effects of sulfoxaflor (a new selective insecticide) and broad-spectrum insecticides on A. glycines and predators in a two-year field experiment. We sampled A. glycines and aphid predator populations using visual whole-plant inspection. In addition, sweep-net sampling was performed to monitor predator populations. To evaluate the toxicity of the insecticides on predator populations, laboratory bioassays were performed on Hippodamia convergens Guérin-Méneville, Orius insidiosus (Say), and Chrysoperla rufilabris (Burmeister). Field results showed that sulfoxaflor was as effective as the broad-spectrum insecticide in suppressing soybean aphid populations and was less impactful on predator populations. The laboratory bioassays showed that sulfoxaflor was moderately harmful to O. insidiosus, harmless to slightly harmful to H. convergens, and harmless to C. rufilabris These studies suggest that sulfoxaflor holds promise for improving integration of chemical and biological controls for A. glycines management.