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Linkage Among Stem and Crown Rust Resistance Genes

Linkage Among Stem and Crown Rust Resistance Genes. Diego Vilar ó , Angela Sebelius, and Michael McMullen NDSU, Plant Sciences. Basis for the Study. Lines with pg-a and B in homozygous condition have not been identified Linkage relationship of N and pg-a. Objective.

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Linkage Among Stem and Crown Rust Resistance Genes

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  1. Linkage Among Stem and Crown Rust Resistance Genes Diego Vilaró, Angela Sebelius, and Michael McMullen NDSU, Plant Sciences

  2. Basis for the Study • Lines with pg-a and B in homozygous condition have not been identified • Linkage relationship of N and pg-a

  3. Objective • Determine pg-a stem rust resistance and B crown rust resistance relationship: • ND873126//ND873126/Morton • Paul//Morton/Paul • Identify a homozygous line for pg-a and B

  4. Genetic Material • ND873126 (pg-a) • Resistance conferred by at least two complementary recessive genes • ‘Morton’ (B) • CRR derived from IAB605X • ‘Paul’ (pg-a, NN) • A component of the pg-a complex appears associated with a gene conferring the naked character

  5. SR and CR Isolates • Stem rust race NA67 • (16,a/1,2,3,4,8,9,13) • Composite of crown rust races • Avirulent on Morton (B) • Virulent on most CR resistance genes

  6. Relationship of pg-a and B • Materials and Methods • ND873126/Morton • F2, BC1F1 and BC1F2 generations • Two sets from different F1 plants • Composite CR and NA67 • Seedling evaluations • Two classes of readings

  7. ND873126/Morton F2 Seedling CR IT • Set #1 • 85R:29S • Data fit the ratio 3R:1S • Set #2 • 195R:60S • Data fit the ratio 3R:1S

  8. ND873126/Morton F2 Seedling SR IT • Set #1 • 29R:85S • Data fit the ratio 1R:3S • One recombinant (CRR-SRR) plant • Set #2 • 69R:186S • Data fit the ratio 1R:3S

  9. ND873126//ND873126/Morton BC1F1CR and SR IT

  10. ND873126//ND873126/Morton BC1F1CR and SR IT

  11. Proposed Inhibitor Gene Linked to a1 19/144 + 19/144 = 0.26

  12. ND873126//ND873126/Morton BC1F1 CR Seedling IT † χ2 to fit various ratios (P=0.05, 1 df). Rejected if χ2 value ≥ 3.84

  13. ND873126//ND873126/Morton BC1F1 SR Seedling IT †χ2 to fit a 1:1 ratio (P=0.05, 1 df). Rejected if χ2 value ≥ 3.84

  14. ND873126//ND873126/Morton Set #1 BC1F2 CR Seedling IT † χ2 for various ratios (P=0.05, 1df). Rejected if χ2 value ≥ 3.84 ¶ Model is B_A1 – I; I 26 cM from A1 Note: No CRS-SRS lines observed

  15. ND873126//ND873126/Morton Set #1 BC1F2 SR Seedling IT † χ2 (P=0.05, 1 df). Rejected if χ2 value ≥ 3.84

  16. ND873126//ND873126/Morton Set #2 BC1F2 CR Seedling IT † χ2 for various ratios (P=0.05, 1df). Rejected if χ2 value ≥ 3.84 ¶ Model is B_A1 - I ; I 26 cM from A1 Note: 23 CRS-SRS lines observed

  17. ND873126//ND873126/Morton Set #2 BC1F2 SR Seedling IT † χ2 (P=0.05, 1 df). Rejected if χ2 value ≥ 3. 84

  18. Relationship of pg-a and B Conclusions • SRR single recessive gene. • CRR single dominant gene • B and A1 are tightly linked. • The model B_A1 – I 26 cM between A1 and I and the simple B_A1 model are proposed from BC1F1 and BC1F2 data.

  19. Relationship of N, B, and a • Genetic Material • Paul – NNbbaa • Morton- nnBBAA • Materials and Methods • BC1 Paul//Morton/Paul • Two sets BC1F1 and one BC1F2 • Composite and NA67 • Two classes • Naked phenotype class

  20. Paul//Morton/Paul BC1F1SR and CR Seedling IT • Data fit the expected 1R:1S ratio for both CRR and SRR

  21. Paul//Morton/Paul BC1F1 Gametic Array and Genotypic Frequencies

  22. Linkage • Recombinant classes N-B-A and n-b-a • 6/46 + 11/46 = 0.37 • b_a

  23. Paul//Morton/Paul BC1F1 Naked or Intermediate Spikelet Classes † χ2 to fit the ratio (P=0.05, 1 df). Rejected if χ2 value ≥ 3.84

  24. Paul//Morton/Paul BC1F2N, B, a

  25. Relationship of N, B, a Conclusions • Morton and Paul differ by one factor for pg-a • b is completely linked to a • N approx. 37 cM from B

  26. Overall Conclusions • SRR conferred by a single gene • CRR conferred by a single gene • B and A and b and a are completely linked • Possible presence of an inhibitor gene 26 cM from A • One CRR-SRR plant was recovered

  27. Acknowledgments • UDSA-ARS National Oat Germplasm Enhancement Project • PepsiCo/Quaker Oats • Pioneer Hi-Bred International, Inc.

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