Project Details:

Title:
Screening Cover Crops to Reduce Soybean Cyst Nematode in Infested Soils

Parent Project: Screening Cover Crops to Reduce Soybean Cyst Nematode in Infested Field
Checkoff Organization:North Dakota Soybean Council
Categories:Nematodes
Organization Project Code:QSSB
Project Year:2019
Lead Principal Investigator:Guiping Yan (North Dakota State University)
Co-Principal Investigators:
Keywords:

Contributing Organizations

Funding Institutions

Information and Results

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Project Summary

Soybean cyst nematode is an important soil-borne disease of soybean in North Dakota and can cause 15-30% yield loss without obvious above-ground symptoms. Managing SCN becomes crucial to reduce economic losses for farmers. Crop rotation and variety resistance are the major farming practices for control of SCN. However, crop rotation does not allow farmers to produce sufficient soybean every year. Resistant varieties could be short-lived because SCN is adapting to the resistance. Cover crops may provide an alternative means to manage SCN. With the funding support from the ND Soybean Council, we screened 21 cover crops for their abilities to host SCN and reduce SCN populations. However, some other important cover crops such as oilseed radish and white mustard haven’t been tested in ND for suppressing SCN. Other vermiform (motile) plant-parasitic nematodes were reported from soybean fields in ND, but the effects of cover crops on these nematodes are unknown. We propose to screen 20 entries of cover crops that are being used or will likely be introduced to ND. The goal of this research will determine or confirm the resistance or susceptibility of cover crops to SCN and determine whether the cover crops are capable of reducing numbers of SCN and other plant-parasitic nematodes in infested fields. The proposed research findings will be useful to navigate the selection and use of cover crops for farmers and the new sources that should be introduced to ND for reducing the damage caused by SCN and other nematodes to increase soybean yield.

Project Objectives

Screen additional cover crops to reduce populations of SCN and other plant-parasitic nematodes in infested fields. Twenty entries of cover crops that are being used or will be likely introduced to North Dakota will be selected for determining or confirming their hosting abilities (resistance or susceptibility) to SCN. Ten cover crops will be selected for evaluating their effects on reducing SCN and vermiform (motile) plant-parasitic nematodes in infested soils.

Project Deliverables

Progress of Work

Updated May 8, 2019:
Objectives of the research

Screen additional cover crops to reduce populations of soybean cyst nematode (SCN) and other plant-parasitic nematodes in infested fields. Twenty entries of cover crops that are being used or will be likely introduced to North Dakota will be selected for determining or confirming their hosting abilities (resistance or susceptibility) to SCN. Ten cover crops will be selected for evaluating their effects on reducing SCN and vermiform (motile) plant-parasitic nematodes in infested soils.

Completed work

Soil samples were collected from two SCN-infested fields in Cass and Richland counties of North Dakota based on our previous work. Nematodes were extracted from soil and counted under a microscope to determine the initial population densities of SCN and other vermiform (motile) nematodes. The soil samples collected from these two fields were used for the greenhouse and microplot experiments.

Twenty-one cover crop species and cultivars plus two susceptible soybean checks, an unplanted control, a wheat cultivar and a corn cultivar were tested in the naturally infested soils from the two fields in the greenhouse. Plants of the 26 entries each in five replicates were grown in a growth chamber for 35 days at 27o C. After 35 days, cysts were extracted from soil and roots in each pot and white females were counted. Eggs were extracted from all cysts in each pot and counted to determine the final population densities. The host range was determined by comparing number of white females in each of the cover crops with the susceptible soybean checks. The effect on population reduction was determined by comparing initial and final population densities.

Ten cover crops (Alfalfa, Chickling vetch, Daikon radish, Faba bean, Flax, Oilseed radish (Concorde, Control, Image), Sunn hemp, White mustard) were selected for the microplot experiments using the infested soils from these fields along with the soybean check Barnes and an unplanted control. These crops were planted in large plastic pots each having 5 kg of soil from each field. After germination, standard seeding rates were used to keep required number of plants per pot. Plants were grown in the greenhouse for two weeks for better establishment before they were moved to the microplot in natural field conditions. The microplot experiments were set up in August. Each of the entries had 5 replications. After 75 days of planting, three soil cores were taken from each pot at the end of October before the snowfall fully killed the plants. All the soil samples are stored in a cold room until SCN eggs and other nematodes are extracted and counted to determine the final population densities.

Preliminary results

Out of the crops tested in the greenhouse, 18 cover crops (alfalfa (cv. Bullseye), balansa clover, berseem clover, winter camelina, faba beans (Petite and VNS), flax, forage oat, Japanese millet, brown mustard (Kodiak), white mustard (Master), daikon radish (Eco-Till), oilseed radishes (Image, Concorde, and Control), pennycress, sunn hemp, white proso millet), corn (DKC44-13) and wheat (Glenn) did not show any reproduction for the SCN populations from the two fields. Two cover crops (Chickling vetch and crambe (BelAnn)) showed limited reproduction with numbers of white females from 1 to 13, but one cover crop (lupine) showed considerable reproduction with white females from 60 to 177. SCN reproduced less in all the tested crops compared to the susceptible soybean checks (Barnes and Sheyenne) with white females from 450 to 888.

When the cover crops were tested in the field soil with the initial population 5,000 eggs/100 cc of soil in the greenhouse, all the tested cover crops except lupine, Chickling vetch and crambe greatly reduced the SCN population (36-94% reduction) compared to the susceptible soybeans and unplanted control (13% reduction). The final populations after planting these cover crops ranged from 3,220 to 320 eggs/100 cc of soil, but the susceptible soybeans (Barnes and Sheyenne) increased the population to 126,300-155,220 eggs/100 cc of soil. When these cover crops were tested in the infested soil with the initial population 3,100 eggs/100 cc soil in the greenhouse, all the tested cover crops except lupine greatly reduced the SCN population (37-91% reduction) compared to the susceptible soybeans and unplanted control (19% reduction). The final populations after planting these cover crops ranged from 1,940 to 280 eggs/100 cc of soil, but the susceptible soybeans increased the population to 77,080-122,880 eggs/100 cc of soil.

From the above controlled greenhouse experiments, all the tested cover crops except lupine reduced the SCN numbers for at least one of the SCN populations. Sunn hemp and oilseed radish (Image) reduced the SCN numbers for the two SCN populations by 91-94% and 71-72%, respectively. These effective cover crops could be used in further field trials and understanding the mechanisms for SCN population reduction.

Work to be completed

Soil samples collected from 120 pots with cover crops and control treatments in the microplot are being processed for nematode assay. SCN and vermiform nematodes will be extracted separately using different extraction methods. We will identify and quantify SCN and other plant-parasitic nematodes from these samples, determine their reproductive factors and calculate the population reduction by these cover crops. The rankings of cover crops tested on reducing SCN numbers and on hosting abilities will be summarized and made available to the soybean farmers at field days, extension meetings, or on extension publications.

Final Project Results

Updated July 3, 2019:

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Research Conducted
Twenty-six entries including 22 cover crops and species, corn and wheat as rotational crops, and two susceptible soybean cultivars were evaluated for host range in a growth chamber by inoculating each plant with 2,000 eggs of two SCN populations from two soybean fields in ND. Ten cover crops were further evaluated in microplot experiments. Crops were planted in pots each containing 5 kg of infested field soil (Figure 2). After 75 days of growth, soil samples were collected from each pot. SCN eggs and other plant-parasitic nematodes were extracted and counted for evaluation of each crop for population reduction.

Why the research is important to ND soybean farmers
SCN is one of the major yield-reducing pests of soybean in ND. Host resistance and crop rotation are common practices to manage SCN, but limited sources of resistance to this nematode put pressure on virulence change in populations to overcome resistance. Thus, integrated management strategy is necessary for sustainable management of SCN. Cover crops may reduce plant-parasitic nematode populations and provide an alternative means to manage SCN.

Final findings of the research
Twenty-one entries (alfalfa, balansa clover, berseem clover, winter camelina, faba beans (Petite and CNS), flax, forage oat, forage pea, Japanese millet, brown mustard, white mustard, daikon radish, oilseed radishes (Image, Concorde, and Control), pennycress, sunn hemp, white proso millet, corn, and wheat) did not support any SCN reproduction, suggesting non-hosts. Chickling vetch and crambe showed low reproduction as poor-hosts, while lupine showed some reproduction, suggesting a suitable host. SCN reproduced less in all tested crops compared to the two susceptible soybean cultivars. All the tested crops significantly reduced SCN populations compared with the susceptible soybean Barnes, but not with the non-planted control (fallow). White mustard, oilseed radish (Concorde, Control), and faba bean (Petite) were more effective than others in population reduction. None of the crops significantly reduced populations of other nematodes in infested soil.

Benefits/Recommendations to North Dakota soybean farmers and industry
Nineteen cover crops and species are identified as non-hosts for SCN. These crops have the potential to be used as cover crops or rotational crops in infested fields to reduce SCN numbers. The experiments will be repeated in 2019 to confirm their population reduction levels. The research findings are useful to navigate the selection and use of cover crops for farmers to reduce SCN damage to increase soybean yield in infested fields.

Benefit to Soybean Farmers

Soybean cyst nematode (SCN) is a very important soil-borne disease for soybean production in North Dakota (ND) and can cause 15-30% yield loss without obvious above-ground symptoms. Managing SCN becomes crucial to reduce economic losses for farmers. Crop rotation and cultivar resistance are the major farming practices for control of SCN. However, crop rotation does not allow soybean growers to produce sufficient soybean every year. Resistant varieties could be short-lived because SCN is adapting to these and new virulent forms can develop and overcome the existing resistance genes. With the use of cover crops for improving soil health in ND, farmers are asking if cover crops can be used to reduce SCN populations in ND.
Cover crops may provide an alternative means to manage SCN. There are multiple mechanisms by which cover crops could reduce the SCN pressure. Cover crops such as radish, mustard and rapeseed can release compounds called glucosinolates and act as a biofumigant that can kill live nematodes when incorporated into soil. Some cover crops encourage SCN eggs to hatch. The hatched juveniles then would starve due to the absence of a host crop upon which to feed. Cover crops may serve as a trap crop for SCN. French marigold is a well-known example serving as a trap crop for controlling root-knot nematode (Tylka, 2014). Oil seed radish has been effective in reducing populations of sugar beet cyst nematode by 80 to 90% and improving sugar beet yields in Michigan (Poindexter, 2011). Reduction of sugar beet cyst nematode was also

observed by using white mustard trap plants (Hemayati et al., 2017). However, the effectiveness using cover crops to control SCN is not well studied.
With the funding support from the ND Soybean Council, we screened 21 cover crops for their abilities to host SCN and to reduce SCN populations. However, some other cover crops such as oilseed radish, white mustard, forage type faba bean, oat, flax, and alfalfa that are being used or will be likely introduced to ND were not included in our tests. Oilseed radish was reported to be very effective for suppressing SCN in European trials (Image Radish Page), but the seed was not available upon request in our previous experiments. Other plant-parasitic nematodes such as root-lesion, spiral and stunt nematodes (Yan et al. 2017a, b, c) were reported from soybean fields in ND, but the effects of cover crops on these nematode species are unknown.
In cooperation with extension agronomists and plant pathologists, we propose to screen additional 20 entries of cover crops that are being used or will likely be introduced to ND. The goal of this research will determine and confirm the resistance or susceptibility of cover crops to SCN and whether these cover crops are capable of reducing numbers of SCN and other plantparasitic nematodes in infested fields. The proposed research findings will be useful to navigate the selection and use of different cover crops for farmers and the new sources that should be introduced to ND. Such information is important to help farmers make the best management strategies for reducing damage caused by SCN and other nematodes to increase soybean yield.

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