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Database Research Summaries

Database Research Summaries
An integrated approach to enhance durability of SCN resistance for long-term strategic SCN management

group Melissa Mitchum (Project leader) and Andrew Scaboo (University of Missouri ) Thomas Baum, Andrew Severin and Greg Tylka, (Iowa State University), Matthew Hudson and Brian Diers (University of Illinois at Urbana-Champaign)
bookmark North Central Soybean Research Program

Research Focus

The widespread lack of genetic diversity in SCN resistance in soybean has significantly increased the prevalence of virulent SCN populations and reduced the effectiveness of current sources of resistance. Thus, we have two major research challenges that, when successfully achieved, will enable us to develop more efficient management practices for this pest in the future:

(1)  Plant breeders need to increase the genetic diversity of SCN resistance in commercially available SCN-resistant soybean cultivars and work with nematologists to determine the most effective rotation practices that preserve these sources,

(2)  Nematologists need to complete the SCN genome (genetic blueprint of the nematode) assembly to facilitate the identification of nematode genes required for the adaptation to reproduce on resistant cultivars, use these as markers to monitor nematode population shifts in the field, and exploit this knowledge to help plant breeders identify novel sources of resistance.

Objectives

1. Diversify the genetic base of SCN resistance in soybean.

A population segregating for Rhg1 and Rhg4 from PI 437654, the genes on chromosomes 15 and 18 from G. soja, and a gene on chromosome 10 from PI 567516C is being evaluated for yield in two locations to test for the impact of these resistance genes on yield. Breeding will be done to incorporate new combinations of resistance genes into high yielding genetic backgrounds.

2. Identify SCN virulence genes to better understand how the nematode adapts to reproduce on resistant varieties.

3. Determine what combinations of resistance genes would be beneficial in variety rotations to enhance the durability of SCN resistance in soybean.

4. Translate the results of objectives 1-3 to the SCN Coalition to increase the profitability of soybean for producers.

5. Coordinate the testing of publicly-developed SCN resistant experimental lines. Field trials in the first year will evaluate different rotation schemes for effectiveness at reducing population densities and the selection pressure on the nematode population.

Results

  • We have developed and commercialized a soybean variety that has the Rhg1 gene combined with the two resistance genes from Glycine soja. This is an important step in providing more genetic diversity in resistant soybean varieties.
  • Field experiments will be to be conducted in Illinois, Missouri, and Iowa in 2019 in order to determine what combinations of resistance genes would be beneficial in variety rotations to enhance the durability of SCN resistance in soybean.
  • The results from the 2018 coordinated performance trials of publicly-developed SCN-resistant experimental lines were analyzed, summarized into a report, and provided to cooperators and other interested parties. Because of the need for breeders to make quick decisions about advancing experimental lines, we made the preliminary analysis available as soon as possible after harvest.
  • We have successfully characterized the genome of the soybean cyst nematode. The work was published in the journal BMC Genetics as The genome of the soybean cyst nematode (Heterodera glycines) reveals complex patterns of duplications involved in the evolution of parasitism genes.
  • The sequencing work was conducted on genomes of five virulent SCN inbred populations that differ in their ability to reproduce on resistant varieties (i.e., different HG types).
  • The successful SCN parasitism relies on syncytium establishment and its continued maintenance via long-term host defense suppression. These complex molecular tasks are accomplished by the SCN by injecting a suite of effectors into the host tissue. Our work has identified a whole suit of previously undiscovered effectors — the nematode-secreted proteins that play critical roles in establishing infection. This is a significant milestone in our understanding of how nematodes overcome host resistance.
  • We can now conduct in-depth functional characterization of the roles played by these effectors, paving the way to the development of new nematode resistance resources in the future.
  • We continue to work on improving our SCNBase website, which make the results of our work available to soybean breeders and researchers.

Importance

  • Growers urgently need more genetically diversified soybean varieties in order to control this pest.
  • Our success in characterizing the genome of the soybean cyst nematode is an important prerequisite for the development of durable resistance against glycines.
  • The results from the regional multi-site testing of publicly-developed SCN-resistant soybean lines will tremendously improve breeding efforts, and will critically inform farmers cultivar decisions.

For more information about this research project, please visit the National Soybean Checkoff Research Database.

Funded in part by the soybean checkoff.