Aphid Resistance in Soybeans

In 2008, the economic loss for the soybean industry due to the presence of aphids was estimated to be approximately 4 billion US dollars annually (Kim et al, 2008). Aphid infestation can decrease soybean yield as high as 50% (Wang et al., 1994; Ragsdale et al., 2007). High aphid populations can reduce crop production directly when their feeding causing severe damage such as stunting, leaf distortion, and reduced pod set (Sun et al., 1990). Although proper use of insecticides can greatly reduce the damaging effects of aphids on soybean yield, this approach is costly (∼33 U.S. dollars/hectare), detrimental for the environment and can lead to the development of insecticide resistant aphids. In addition, this practice could also adversely affect the population of insects that normally prey on aphids (Ragsdale et al., 2007).

Aphis glycines, and a close relative A. gossipii, are the only aphid species found colonizing soybean in the Unites States (Hill et al., 2004). To date, four soybean aphid biotypes are now known in relation to resistance genes. Depending on the type of soybean aphid, there are different resistance gene combinations from the soybean plant that offer tolerance to these pests.

The use of soybean lines naturally resistant to aphids is another management approach to control soybean aphids. By selecting the varieties that are resistant to the biotypes of aphids most prevalent in ND, farmers will decrease aphid damage and decrease yield losses due to aphids. Farmers will decrease insecticide applications reducing costs and impact on the environment.

Scientists at the NAGC have optimized high throughput assays to screen soybean varieties for Rag1, Rag2, Rag3 genes. From the genetic work of our collaborator, Dr. Brian Diers (University of Illinois-Urbana) and research from Dr. Dechun Wang (Michigan State University), identification of genetic markers linked to the Rag genes have made it possible to rapidly screen new soybean varieties for aphid resistance.

This project was funded in part by the North Dakota Soybean Council.


Zhang S., Z. Zhang, C. Bales, C. Gu, C. DiFonzo, M. Li, Q. Song, P. Cregan, Z. Yang and D. Wang. 2017. Mapping novel aphid resistance QTL from wild soybean, Glycine soja 85-32. Theoretical and Applied Genetics, 1-12.

Bacterial Leaf Streak

The NAGC collaborated with the USDA and university labs to identify Xanthomonas in corn, the causal agent that causes Bacterial Leaf Streak in Corn. As the top corn producing country, there is a strong need to provide US farmers with reliable and early disease detection for a variety of pathogens, particularly for the recently confirmed Bacterial Leaf Streak Disease (BLSD).  BLSD is caused by a bacteria, Xanthomonas vasicola pathovar vasculorum (Xvv), which was thought to be restricted to South Africa. The first reported detection of Xvv in the US was in Nebraska last year (2016) and further surveying has confirmed its presence in several other states (Minnesota, South Dakota, Iowa, Colorado, Illinois, Kansas, Texas and Oklahoma) with more being added (USDA-APHIS, 2016, August 29 and Institute of Agriculture and Natural Resources, University of Nebraska-Lincoln, 2016, August 26). Symptoms of BLSD are similar to other diseases, making visual diagnosis difficult to impossible.

Due to its recent introduction to the US, the epidemiology (control and spread) of BLSD is largely unknown, but it is likely that foliar fungicides typically used against gray leaf spot will be ineffective against this bacterial disease.

Through the USDA’s collaboration, the NAGC has been able to modify the initial assay to allow for a greater number of samples (high throughput) to be analyzed in a shorter period of time. The information gathered will allow for a better understanding of the transmission of the disease and protect producers from further spread within the US. There are only a few research labs that can support and are capable of developing high throughput assays using the latest molecular instrumentation that the NAGC possesses. This assay has the potential to screen other plants that may not yet be identified as alternative hosts (e.g. cotton, food crops or weeds) to the bacteria, which have been important sources in particular strains of Xanthomonas vasicola pathovars (Coutinho, et al., 2015).

Importantly, optimization of the assay will enable producers to test a variety of potential contaminated sources (farming equipment, seeds, soil), which can help market corn for exportation as well as assert liability of contamination from farming equipment that moves from field to field. Furthermore, this assay will provide a more reliable diagnosis, allowing producers to be more proactive in their management strategies.

This project was funded by the National Corn Growers Association and the North Dakota Corn Council.


Lang J., E. DuCharme, J. Ibarra Caballero, E. Luna, T. Hartman, M. Ortiz-Castro, K. Korus, J. Rascoe, T.A. Jackson, K. Broders, J. Leach. (2017). Detection and characterization of Xanthomonas vasicola pv. vasculorum (Cobb 1894) comb. nov. causing bacterial leaf streak of corn in the United States. Phytopathology. 2017 Jul 5. doi: 10.1094/PHYTO-05-17-0168-R.

Goss’s Wilt

Clavibacter michiganensis subsp. nebraskensis (Cmn), the causal organism of Goss’s Wilt, can infect a corn crop in any developmental stage, whether through wounds or transmitted directly through seed. Once the bacteria has colonized a crop, the surface-infested crop residue later becomes the main source of inoculum for future outbreaks of Goss’s wilt and leaf blight.

NAGC has optimized a test for Goss’s Wilt with high throughput capabilities that was very recently developed by a group from the University of MN (McNally et. al., 2016), which utilized a PCR-based assay to detect, identify and quantify the causal agent of Goss’s Wilt (Cmn). Utilizing the Goss’s Wilt assay, NAGC is able to provide an accurate, sensitive and affordable method for producers and researchers to assess the potential for developing Goss’s Wilt as a pre-screen of seed before purchase, for detecting the organism in field samples to assess the bacterial lode in the field before planting, as well as detecting the organism on symptomatic plant samples.

This project was funded in part by the North Dakota Corn Utilization Council.


McNally, R.R, C.A. Ishimaru and D.K. Malvick. 2016. PCR-mediated detection and quantification of the Goss’s Wilt pathogen Clavibacter michiganensis subsp. nebraskensis via a novel gene target. Phytopathology 126:1465-1472.

Gray Leaf Spot and Bacterial Leaf Streak Multiplex

Gray Leaf Spot (GLS) is a destructive foliar disease caused by two closely-related fungal species Cercospora zeae-maydis and Cercospora zeina, which have different distributions in North America. C. zeae-maydis is thought to be found throughout North America compared to C. zeina, which appears to be restricted to the eastern Corn Belt. When plants are infected by either species, GLS first manifests as small pinpoints, which eventually turn into brownish-gray, rectangular lesions. Once infected, plants continually shed GLS fungal spores throughout the growing season, which can be transferred to adjacent plants or fields by wind-driven rain. During periods of high humidity and moderate temperatures, large GLS outbreaks can occur. Fungicides have been shown to be effective against GLS.

NAGC has developed a real-time PCR multiplex assay for the detection of Cercospora zeae-maydis (Czm) and Cercospora zeina, two groups of pathogens that cause Gray Leaf Spot (GLS) in corn along with the Bacterial Leaf Streak (Xanthomonas) assay. By combining the detection of GLS along with the detection of Xanthomonas vasicola pv. vasculorum, a corn pathogen that causes Bacterial Leaf Streak, into a single assay, allowing for rapid and accurate discrimination of the two pathogens that may be misdiagnosed in corn foliar diseases.

This project was funded by the National Corn Growers Association and the North Dakota Corn Council.


Lang J., E. DuCharme, J. Ibarra Caballero, E. Luna, T. Hartman, M. Ortiz-Castro, K. Korus, J. Rascoe, T.A. Jackson, K. Broders, J. Leach. (2017). Detection and characterization of Xanthomonas vasicola pv. vasculorum (Cobb 1894) comb. nov. causing bacterial leaf streak of corn in the United States. Phytopathology. 2017 Jul 5. doi: 10.1094/PHYTO-05-17-0168-R.

Korsman, J., B. Meisel, F.J. Kloppers, B.G. Crampton and D.K. Berger. 2012. Quantitative phenotyping of grey leaf spot disease in maize using real-time PCR. European Journal of Plant Pathology 133:460-471.

Honey Bee Pathogen Multiplex Panel

The Honey Bee Pathogen Panel is currently offered to consumers on a fee for service basis. This test panel was developed by NAGC as a tool used to screen for the health of honey bees. NAGC’s pathogen panel is specific for the following 11 viral and bacterial pathogens:  Acute Bee Paralysis Virus, Black Queen Cell Virus, Kashmir Bee Virus, Lake Sinai Virus 1 and 2, American Foulbrood, Chronic Bee Paralysis Virus, Deformed Wing Virus, Israeli Acute Bee Paralysis Virus, Slow Bee Paralysis Virus and European Foulbrood. This multi-target panel has been shown to be highly specific for each target using the unique DNA sequence from each pathogen. In addition to the cost savings, the utilization of a multiplex panel shortens the turnaround time which, in turn, heightens the throughput capacity of the laboratory.

In parallel to developing the multiplex panel for quick and reliable testing, NAGC has also conducted a 10-week study exploring storage conditions of honey bees to determine the acceptable parameters for storage, transit and detection. The preliminary data suggests that the pathogens were still detectable after 10 weeks stored at room temperature (~70°F) without any decrease in sensitivity. These samples were compared to samples stored at the colder storage recommendations of -20°C and 4°C. NAGC also investigated higher than room temperature storage and those conditions are not recommended. They hope this new data will help support less stringent guidelines for testing and hopefully open the opportunity to testing for beekeepers that may not have access to cold transit shipping conditions.

This project was funded by the National Corn Growers Association and the North Dakota Department of Agriculture.


Chantawannakul P., L. Ward, N. Boonham and M. Brown. 2006. A scientific note on the detection of honeybee viruses using real-time PCR (TaqMan) in Varroa mites collected from a Thai honeybee (Apis mellifera) apiary. Journal of Invertebrate Pathology 91: 69-73.

de Miranda, J.R., G. Cordoni and G. Budge. 2010. The Acute bee paralysis virus-Kashmir bee virus-Israeli acute paralysis virus complex. Journal of Invertebrate Pathology 103: S30-S47.

Roetschi A., H. Berthoud, R. Kuhn and A. Imdorf. 2008. Infection rate based on quantitative real-time PCR of Melissococcus plutonius, the causal agent of European foulbrood, in honeybee colonies before and after apiary sanitation. Apidologie 36: 362-371.

Runckel, C., M.L. Flenniken, J.C. Engel, J.G. Ruby, D. Ganem, R. Andino and J.L. DeRisi. 2011. Temporal analysis of the honey bee microbiome reveals four novel viruses and seasonal prevalence of known viruses, Nosema and Crithidia. PLoS ONE 6:e20656.

Ryba S., D. Titera, M. Haklova and P. Stopka. 2009. A PCR method of detecting American Foulbrood (Paenibacillus larvae) in winter beehive wax debris. Veterinary Microbiology doi:10.1016/j.vetmic.2009.05.009.

Tentcheva, D. L. Gauthier, N. Zappulla, B. Dainat, F. Cousserans, M.E. Colin and M. Bergoin. 2004. Prevalence and seasonal variations of six bee viruses in Apis mellifera L. and Varroa destructor mite populations in France. Applied and Environmental Microbiology 70: 7185-7191.

Northern Corn Leaf Blight

Exserohilum turcicum is a destructive fungal pathogen that infects leaves of corn, sorghum and grass species. As the causal agent of Northern Corn Leaf Blight (NCLB), yield losses associated with this disease can be extensive, upwards of 50% in susceptible hybrids when the disease develops early in the season, prior to tasseling. However, when disease severity is minor or its development has been delayed until well after silking, yield impacts are usually minimal. The ideal conditions for NCLB include high humidity under the canopy with moderate soil temperatures. Having a history of NCLB in the field or in nearby fields is the most important factor impacting disease development. The ability of the fungusto survive from year to year in infected corn residue makes it a perpetual problem once the disease has developed in the area.

In-field symptoms of NCLB can be mistaken for other pathogens, including gray leaf spot (Czm) and bacterial leaf streak (Xvv). With no way to eradicate the fungus from a location, management of NCLB becomes the focus, especially since the effectiveness of in-season treatments (fungicide applications)may rely on early and accurate diagnosis.


Phytophthora root and stem rot (PRSR), caused by the soil-borne fungus Phytophthora sojae is a common disease found throughout the United States. PRSR has been ranked as a leading destructive soybean disease reportedly causing an annual loss of over 44 million bu from 1996-2009 (Koenning and Wrather, 2010; Wrather and Koenning, 2009).

The NAGC has developed a test that allows for the identification of the Phytophthora pathogen, allowing ND soybean producers to quickly identify the Phytophthora pathogen. An accurate course for remediation can then be determined. It can also be an indicator of what soybean producers might expect in a particular field the following year.

This project was funded in part by the North Dakota Soybean Council.


Catal, M., F. Erler, D. Fulbright and G. Adams. 2013. Real-time quantitative PCR assays for evaluation of soybean varieties for resistance to the stem and root rot pathogen Phytophthora sojae. European Journal of Plant Pathology, 137, 859-869.

NAGC Fee Schedule
Honey Bee Testing

    Full Screen………………………………………………………………$75/Sample

    Multiplex Group 1……………………………………………………$50/Sample

    Multiplex Group 2……………………………………………………$50/Sample

    Multiplex Group 3……………………………………………………$40/Sample

    Any Single Pathogen Test………………………………………..$20/Sample

    Bulk Pricing (full screen)……………………………………………$50/Sample

Plant Testing

    Plant Tissue & Seeds……………………………………………….$30 to $90/Sample

    Soil & Residue…………………………………………………………$40 to $120/Sample


Printable NAGC Fee Schedule 

Test Codes for Submission Form

Honey Bee Pathogen Panel Codes:

A = Honey Bee Full Screen;

B = Multiplex Group 1;

C = Multiplex Group 2;

D – M = Singleplex Tests; D = ABPV; E = KBV; F = BQCV; G = LSV-1/LSV-2; H = AFB; I = SBPV; J = CBPV; K = IABPV; L = DVW; M = EFB

Multiplex Group 1 = ABPV, BQCV, KBV, LSV-1/LSV-2, and AFB

Multiplex Group 2 = CBPV, DWV, IAPBV, and SBPV.

ABPV = Acute Bee Paralysis Virus; KBV = Kashmir Bee Virus; BQCV = Black Queen Cell Virus; LSV-1/LSV-2 = Lake Sinai Viruses 1 and 2; AFB = American Foulbrood; SBPV = Slow Bee Paralysis Virus; CBPV = Chronic Bee Paralysis Virus; Israeli Acute Bee Paralysis Virus (IABPV), Deformed Wing Virus (DWV), and European Foulbrood (EFB).


Corn Assay Test Codes:

GW = Goss’s Wilt

GW-Q = Goss’s Wilt Quantitative

GLSx = Gray Leaf Spot and Xanthomonas vasicola pv. vasculorum Multiplex

GLS-Q = Gray Leaf Spot Quantitative

Xvv-QXanthomonas vasicola pv. vasculorum Quantitative Analysis

NCLB-Q = Northern Corn Leaf Blight Quantitative


Soybean Assay Test Codes:

Ps = Phytophthora sojae

AR = Aphid Resistance in soybean