New genes for resistance to SCN

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Soybean Cyst NematodeManaged Research Area

Center of Excellence for Soybean Research,
Teaching and Outreach Southern Illinois
University Carbondale
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Variety Evaluation
369 varieties from the state variety
trials Screened against 4 populations of SCN
Race 3 (2 pop.), Race 1 and Race 5 Number of
cysts on each variety counted and compared to a
standard susceptible

• Deliverables
• Variety information submitted to VIPS
• Resistance information for Races 1, 3, 4, and 5

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Level of resistance of 300 proprietary varieties
in VIPS to SCN Race 3 (HgType 7). G. Noel, 2002.
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SDS/SCN Interaction
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SDS/SCN Interaction
Isolines ExF11-1 ExF11-32 ExF20-16 ExF20-32
Pathogens SCN none, low, high FSG none,
low, high
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SDS/SCN Interaction
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Variety Development
Joint programs at UIUC and SIUC Both programs
have released SCN-resistant varieties. Many
lines are resistance to SDS, high yielding and
contain genes from Peking, PI 88788, PI 437654,
PI 89772, PI 90763, PI 209332 or PI 404166
The goals of the programs are to release
varieties with a high level of resistance and
maintaining a diversity of resistance.
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Yield Drag Study Greg Noel
USDA, ARS, and UIUC

• - Seven farms
• Four varieties susceptible, Peking resistance,
• PI88.788 resistance high and low
• Field length ranged from 400 ft. to 2,400 ft
• Three replications

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Grace Farm, 2002
Susceptible 62.8 bu/A Pi 0 eggs
PI88.788-low 57.7 bu/A Pi 2 eggs
Peking 54.1 bu/A Pi 10 eggs
PI88.788-high 57.1 bu/A Pi 0 eggs
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University of Illinois Farm, 2002
Peking 54.2 bu/A Pi162 eggs
PI88.788 low 51.0 bu/A Pi216 eggs
Susceptible 51.0 bu/A Pi220 eggs
PI88.788 high 55.1 bu/A Pi71 eggs
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Cultural PracticesSCN - SDS
Rotation with non-hosts (corn wheat) Multiple
years with non-hosts Various sequences
Cover crops and green manures Wheat, Rye,
Rapeseed
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New Resistance GenesKhalid Meksem

• New genes for resistance to SCN
• Functional analysis of soybean genes involved in
  SCN resistance
• Characterization of virulence genes

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New Genes for Resistance

• Glycine soja x G. max PI468916 x A81-356022
  population.
• Three genomic regions were identified as
  possessing new SCN genes
• Populations are being developed for fine mapping
• This will increase the diversity of SCN
  resistance genes in soybean

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Candidate Gene Approach

• Of three genes identified from PI468916, one was
  mapped to linkage group G, the common genomic
  region for SCN resistance
• Other candidate genes will be mapped using this
  method in the Glycine soja x G. max PI468916 x
  A81-356022 population

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Outcomes and Benefits

• The DNA markers will increase the efficiency in
  selecting for these new Rhg genes
• New sources of SCN resistance will be provided to
  breeders and producers.

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Analysis of Resistance Genes (rhg1 and
Rhg4)David A. Lightfoot
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SCN Resistant Sources

• Peking (Forrest, Pharaoh) and PI437654 (Cyst X,
  Hartwig) have an identical Rhg1 alleles (R type
  1).
• PI88788 (Fayette, Jack) and PI 209332 (Faribault)
  have an identical Rhg1 (R type 2).

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SCN Resistant Sources

• Genetic fine mapping has identified different
  alleles at the Rhg 1 locus (linkage group G)

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SCN Resistant Sources

• There are 92 PIs from China that are resistant to
  SCN
• Some have different resistance alleles at Rhg 1
• We are testing to find which have new alleles
• Two new resistance alleles have been found.

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Conclusions

• Currently there are two Rhg1 alleles available to
  producers
• These alleles can be rotated to improve yield and
  extend the useful life of resistance
• Additional alleles may be available from Chinese
  PIs