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Heterodera glycines

Heterodera glycines. Soybean Cyst Nematode:. Heterodera glycines. Soybean Cyst Nematode:. Still Soybean Thief and Public Enemy Number One. Nationally, considered to be the most damaging soybean pest in U.S. Importance. Present in 49 counties and all major soybean counties.

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Heterodera glycines

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  1. Heterodera glycines Soybean Cyst Nematode:

  2. Heterodera glycines Soybean Cyst Nematode: StillSoybean Thief and Public Enemy Number One

  3. Nationally, considered to be the most damaging soybean pest in U.S.

  4. Importance • Present in 49 counties and all major soybean counties. • Caused an estimated 1.12 mil bu (1.75%) yield loss in 2006. • Most KY soybean producers don’t give SCN a second thought, • but almost every acre is planted to a SCN resistant bean.

  5. Source of damage • Nematodes infect roots: • Restricts nutrient and water uptake. • Roots mass is reduced and roots are less vigorous; fewer healthy N-fixing nodules are produced. • Diseased roots more susceptible to other soil-borne pathogens. • Affected plants grow slower and plants yellow prematurely. • Stressed plants produce fewer and smaller seed, resulting lower yields.

  6. Up to 40% yield loss can occur with NO visible symptoms

  7. Quick Life Cycle Primer

  8. Female on Way to becoming a cyst Cyst (Dead Female)

  9. External eggs in gelatinous matrix

  10. Water and nutrients Root with Nematode Feeding

  11. ~30 –days to complete life cycle under • optimal conditions. • 2-3 cycles per season because much of the season is less than optimal for SCN development.

  12. Current Status of SCN • 90+% of SCN-resistant varieties in MG 3,4, and 5 have PI88788 in their background. • Peking-based varieties next most common. • Varieties based on PI88788 have been heavily deployed since the late 1980’s . • Historical SCN populations in most states were effectively managed using PI88788-based resistant varieties. • Recent data in IL, IN, and MO suggest that SCN is “adapting” to PI88788- (and Peking-) based varieties.

  13. Distribution of SCN Types in Illinois *Sikora and Noel (1991) J. Nematol. 23:624-628.

  14. Missouri Findings - 2005 • 122 samples collected from 47 counties: • 61% of samples had egg counts that were high to very high (i.e., yield limiting). • 13% had low populations • 26% had no detectable SCN. • In 20 HG tests: • 85% had significant reproduction on PI88788. • 35 had significant reproduction on Peking. • 62% of Missouri producers did not believe they were losing any yield to SCN.

  15. Recent Indiana Findings

  16. So what’s the big deal?

  17. USDA soybean collection HG Type 0 (old race 3) Female Index is a measure of aggressiveness. UIUC

  18. Southern Illinois University HG Type 2.5.7 (more aggressive population) The big deal is that the vast majority of SCN-resistant varieties are losing their effectiveness.

  19. University of Illinois SCN Screening2006 Results by Resistance Category (Old race 3)

  20. KY SCN RESPONSE • In spring of 2006-07, 139 samples from 19 counties (representing 694,000 acres) were collected by ANR agents. • Fields were in corn in 2005. • Targeted for soybean production in 2006-07. • 20 populations, representing 8 counties, were sent to the University of Missouri Nematology Lab for HG-Typing. • Funded by KSPB.

  21. Heterodera glycines HG-Type Test Establishes overall ability of SCN populations to reproduce on 8 SCN- resistance “types” relative to a susceptible check. Done under controlled conditions. Takes 30 days to complete

  22. HG-Type results based on “Female Index” Number of cysts on resistant line Number of cysts on a susceptible variety • Female Index: • 10%is cutoff for +/- • 30% indicates cultivars with this source of resistance would have significant yield reductions. Female index =

  23. Actual HG-Type Test Example from Carlisle County - 2006

  24. 2006 KY Survey Results • Out of 139 samples collected 76% had detectable levels of SCN. • 27% had SCN levels above the established damage threshold of 500 eggs/250 cc soil). • Out of 20 HG-Type tests: • All populations reproduced on PI88788. • 60% had FI’s of >30 on PI88788. • 25% had FI’s of >50.

  25. Races Represented • Race 1: 12/20 samples (60%) • Race 2: 5/20 samples (25%) • Race 5: 3/20 samples (15%) • Race 3: 0/20 samples (0%) • Race 14: 0/20 samples (0%)

  26. What does it all mean? • We’ve got problems brewing and it is time to rethink how we are using resistant varieties in Kentucky. • Time to start soil sampling again. • Must avoid the worst-case scenario at all costs.

  27. HG Type .4. Female Indices 4 = PI437654

  28. Adaptation of SCN to PI437654 in Illinois

  29. How would this population shift occur? • No resistant variety is immune to SCN; there are always some individuals able to reproduce on roots of resistant plants. • Population shifts occur when more aggressive individuals in a population are favored and less aggressive individuals are not. • Populations shift to more aggressive individuals over time (1-3 years). • This “selection pressure” increases with increasing resistance levels in plants.

  30. Seem hopeless? • Not really. • The risk of Type 4 SCN populations can be greatly reduced by infrequent use of “Hartwig” resistance (PI437654). • Once every 6-10 yrs? • If SCN levels get very high, it is better to go to a non-host for 2 or more years. • Use other, “less resistant” varieties on routine basis, but:

  31. Do not plant the same resistant variety each time you plant soybean. • If possible, select varieties that represent different sources of SCN resistance: • Something that does not have PI88788 as the exclusive source of resistance in its background. • Remember to avoid overusing of “Hartwig resistance” • Some researchers are looking at custom blends representing different sources of SCN resistance.

  32. Information on source of SCN resistance http://web.extension.uiuc.edu/livingston/reports/i120/index.html

  33. Best SCN Management Options • Continue rotating soybean with a non-host crop. • Corn, grain sorghum, alfalfa, fescue, etc. • Following a non-host crop, if the field is going to be in soybean the next season, have an SCN test done. • If SCN density is much above 3000 eggs/250 cc soil after a year of corn, this suggests something is wrong. • Population was able to significantly reproduce on the last SCN-resistant soybean you grew two years earlier. • SCN host weed problems.

  34. Best SCN Management Options • Seek out and plant varieties with proven performance (both SCN and yield). +12% +4% Bu/A 2006. Niblack, University of Illinois; 685 entries, 13 locations

  35. Public information on the performance of varieties in presence of SCN is in very short supply. Reputable private companies may be the only source of available performance information. Small seed companies usually lack the resources to test SCN varieties against more than just 1 or 2 populations.

  36. Final Thoughts • SCN can never be eliminated from a field. • Populations can be managed and we have the technology to do so. • Periodically sample fields and monitor how your SCN mgmt. program is doing. • HG-typing may help answer some questions, but you may need help interpreting the results (cost $100). • Most problems result from not paying attention to the finer points of SCN mgmt.

  37. BEST WISHES for 2008!

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