Performing Department
ENTOMOLOGY
Non Technical Summary
Soybean cyst nematode (SCN, Heterodera glycines) is one of the most devastating pathogens of soybean in the world, causing more than 1 billion dollars of yield losses each year in the USA. Although plant resistance is the primary and most effective strategy against SCN, it's crucial to recognize that many SCN populations have adapted to this approach over time. Therefore, the evaluation of alternative SCN management strategies becomes essential. Our previous research on root lesion nematodes and our preliminary laboratory studies on SCN have demonstrated a significant reduction of nematode numbers using specific manure-based composts. In our pursuit of effective solutions, we've isolated bacteria from these composts and are actively assessing their influence on egg hatching. Additionally, greenhouse experiments have demonstrated that cover crops can significantly reduce SCN egg counts compared to susceptible soybean controls. So, we will conduct thorough evaluations of sustainable treatments, including composts and manures, bacteria isolated from these organic materials, and cover crops, to determine their effectiveness in managing SCN populations. Furthermore, our Michigan survey detected second-stage SCN juveniles in several wheat root samples. We aim to assess wheat's impact on SCN populations and explore its potential as a trap crop. Our project will also involve conducting a comprehensive statewide survey in Michigan to assess the populations, distribution, HG types, and the factors influencing the presence of SCN. We will share the findings of this study with growers, stakeholders, nematologists, and extension faculty members through extension bulletins, publications, and talks at farm conventions in four soybean-producing states.
Animal Health Component
0%
Research Effort Categories
Basic
10%
Applied
90%
Developmental
(N/A)
Goals / Objectives
We will evaluate different cover and trap crops, compost/manures, and their bacteria to determine their ability to reduce SCN nematode populations and contain their spread. We aim to (1) gather crucial data on SCN prevalence, distribution patterns, HG type diversity, and the factors that contribute to their presence in Michigan; (2) reduce soybean growers' risk of economic loss from the invasive nematode by developing multiple management strategies; and (3) deliver the findings of this proposal to soybean growers through collaborations with extension faculty at various universities. We will achieve these goals by pursuing three specific objectives:Objective 1. Conduct a comprehensive Michigan-wide survey to assess SCN populations, distribution, HG type, and factors influencing their presence. a. Evaluate the prevalence and density of SCN populations across different regions in Michigan. b. Map the distribution patterns of SCN populations in Michigan. c. Identify the diversity of HG types within SCN populations. d. Determine the effect of factors such as resistant cultivars, cover crops, and chemical nematicides on the prevalence of SCN in soybean fields.Objective 2. Reduce SCN population levels and increase crop yields with the use of trap crops, cover crops, manures, and their bacteria. a. Determine the potential of wheat as a trap crop for SCN by conducting controlled experiments in greenhouse environments. b. Ascertain the influence of winter wheat on crucial aspects of SCN behavior, such as egg laying rate and population dynamics, to clarify their impacts on nematode growth. c. Determine the effectiveness of different varieties of oilseed radish and four cover crops to serve as trap crops for SCN in laboratory and greenhouse trials. d. Determine the type, optimal application rate, and time for composts/manures for control of SCN in greenhouse trials. e. Determine the effect of isolated bacteria on SCN population and plant growth under greenhouse conditions and identify selected bacteria using molecular methods. f. Identify optimal management practices in field and outdoor microplot trials using trap crops, cover crops, and composts/manures and their bacteria.Objective 3. Extend the knowledge acquired by this research to growers, agricultural professionals, and scientists in soybean growing regions in the U.S. a. Conduct a pre- and post-implementation survey with growers from Michigan, Wisconsin, and Illinois. b. Organize field days to educate growers from participating states on research and management strategies for SCN. c. Present annual updates on trial results at relevant industry meetings through extension talks, publications, posters, and oral presentations
Project Methods
Design: Experiment 1.1. For the surveywe will collaborate with Michigan Soybean Committee and extension agents to compile a list of growers from each of the soybean districts. We plan to administer our questionnaire about the growers' location, sample location, typical rotation practices, soybean varieties grown, and use of cover crops, nematicides, composts, and more.Experiment 1.2: To determine the HG type of the SCN population, reproduction of the SCN population is measured on "HG type indicator" soybean lines (Table 1) with SCN resistance genes. We will submit the samples to the MSU diagnostic lab to determine HG type test.Measures: SCN survey: We will extract the nematodes to determine the population counts. We will conduct HG type testing.Furthermore, we will compile the datato identify trends in SCN distribution, population dynamics, and HG type prevalence. Finally, we will share our findings from this survey with farmers and growers. We will organize field days, conduct extension talks, and deliver oral presentations.HG type test: Samples will be sent to the MSU diagnostic lab for HG type testing.Experiment 2.1. To determine theutility of wheat as a trap crop, we will initiate greenhouse experiments involving selected wheat varieties. We will plant these varieties, along with susceptible soybean controls, in 0.67-gallon pots. Aftergermination, we will inoculate six pots per variety with 2,000 SCN eggs per liter of soil. One pot will remain untreated. After eight weeks, we will evaluate visual indicators and collect soil (100 cm3 ) and root (two grams) samples from each container for nematode extraction via centrifugation (Jenkins, 1964) and count the nematodes under a microscope.Experiment 2.2. We will use soil and root samples toevaluateof how wheat cultivation affects nematode egg hatching and development. We will quantify the population of J2 in soil through nematode extraction and microscopic counting, comparing differences between wheat cultivated soil and control soil. Wheat roots will also be stained with acid fuchsin to visualize nematode development within the roots, including third and fourth stage juveniles and adult females. At least five plants will be analyzed per treatment. We will count developmental stages and numbers of nematodes within the roots under a dissecting microscope and compare the numbers between wheat and control treatments.Experiment 2.3. To test if cover crops influence SCN hatching, we will place 1,000 fresh SCN eggs in a hatching chamber designed by Behm et al. (1995) and Thapa et al. (2017) to collect SCN J2s. Distilled water will be a negative control and soybean root excaudate and ZnCl2 3mM (as a hatching stimulant) will serve as a positive control. To determine the effect of cover crops on the survival of SCN J2s, approximately 200 J2 nematodes will first be exposed to 100% cover crops root excaudate within 50mL centrifuge tube arenas for 7 days. These experiments will have five replications in a randomized complete block design.Experiment 2.4. Manures and composts including poultry manure, swine manure, layer ash blend, Sili-K, worm doo, seed starter, layer manure and high carbon dairy doo will be tested in this proposal. Two laboratory trials will be conducted to determine how different rates of composts/manures influence SCN's hatching response and the survival of J2s. Products will be tested at six rates.Five replicates will be tested for each treatment in a randomized design. Composts will be homogenized with play sand . We will conduct these experiments using the approach described in experiment 2.2.Experiment 2.5. To isolate the bacteria, 5 µl of extracted solution will be cultured on nutrient agar (NA) and incubated for 48 h at 28 °C (Rostami et al., 2021). Single colonies from each plate will be observed and selected based on morphological characteristics. Pure bacterial cultures will be obtained by repeated streaking on fresh NA agar plates. Pure bacterial colonies will be preserved on NB medium with 30% (v/v) glycerol at −80 °C (Yazdani et al., 2018). Both experiments will be conducted following the approach described in Experiment 1.1 above and bacteria suspensions (108 CFU/ ml) will be added to each petri-dish of the hatching chamber. For the greenhouse study, susceptible soybean seeds will be planted in 0.67-gallon pots containing mixed soil (soil and sand, 1:3). Plants at the four-leaf stage will be inoculated with 20 ml of bacteria suspensions (108 CFU/ml) or 50 ml of manure extract (100%) per pot. Three days later, each pot will be inoculated with 6000 SCN eggs.Experiment 2.6. A field experiment will be conducted on a farmer's field located in Monroe, Michigan, withhigh SCN incidence. Microplot studies will be conducted in the Entomology farm at MSU andonSouthern Illinois University Carbondale. We will use the data from the bioassay trials outlined in Experiments 2.1-2.5 to select the most promising wheat varieties, composts/manures and their bacteria isolates and cover crop treatments. This study will confirm their efficacy for managing SCN at a field level. Soil from multiple locations on a SCN infested soybean farm will be collected before the trial to ensure we select a plot with a high nematode density.Measures: Confirmation of SCN. We will initially identify nematodes by morphological characterization of the genus Heterodera, before using molecular markers to identify them at a species level. We will extract nematode genomic DNA using the protocol published by Janssen et al. (2017).Greenhouse trial. After an incubation period of eight weeks, we will observe and record any visual symptoms such as changes in plant vigor, height, and dry and fresh weights of the top part of the plant. We will then collect soil samples of 100 cm3 and two grams of roots from each container. We will extract nematodes from the soil by centrifugation using the method described by Jenkins (1964) and count them under a microscope. The greenhouse trial will be repeated.Laboratory tests. To determine the impact of cover crops, compost/manure products, their varying concentrations, and bacterial isolates on the hatching of SCN eggs, the number of hatched J2s will be counted every three days for one-month intervals. For the second trial, the effect of composts/manures on the survival of SCN J2s will be determined by placing the composts onto a modified Baermann funnel, collecting the surviving nematodes, and calculating the survivorship rate. The composts will be placed on a tray for seven days to collect the surviving nematodes and determine the survivorship rate. These trials will be repeated once more, and the products that perform the best will be selected for a field trial.Field trial. The field trial will entail collecting initial and harvesting soil samples each year to determine nematode population density. Soil samples will be obtained by a composite of 10 soil cores using a soil probe in a zig-zag pattern from the root zone. Cysts and J2s will be extracted from 100 cm3 soil subsamples of each sample using a modified centrifugation-flotation technique (Jenkins, 1964), and the number of J2s and cysts will be recorded.Statistical analysis: To evaluate the differences between the means of the data, we will use the analysis of variance (ANOVA) and least significant difference (LSD) tests. Statistical significance will be determined at the P < 0.05 level. All statistical analyses will be conducted using SPSS 28.0.Extension activitiesTo assess the impact of our findings and disseminate knowledge to soybean growers in Michigan, Wisconsin, and Illinois we will administer pre- and postimplementation surveys.Measures: We will assess the effectiveness of our knowledge dissemination and growers' adoption of our recommended management practices through pre- and post-event grower questionnaires conducted during in-person talks and field days.