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Suppression of rust resistance in wheat

Suppression of rust resistance in wheat. Mina Talajoor Department of Plant Sciences & Plant Pathology Montana State University. Origins of Wheat. Triticum turgidum (2n=4x, AABB) . Triticum urartu (2n=2x, AA). Triticum aestivum (2n=6x, AABBDD). Aegilops tauschii (2n=2x, DD).

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Suppression of rust resistance in wheat

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  1. Suppression of rust resistance in wheat Mina Talajoor Department of Plant Sciences & Plant Pathology Montana State University

  2. Origins of Wheat Triticum turgidum (2n=4x, AABB) Triticumurartu (2n=2x, AA) Triticum aestivum (2n=6x, AABBDD) Aegilopstauschii (2n=2x, DD) Aegilopsspeltoides (2n=2x, SS) Photos courtesy of Li Huang

  3. Wheat Rust Obligate biotrophic fungus • Leaf Rust Pucciniatriticina

  4. Wheat Rust Obligate biotrophic fungus • Leaf Rust • Stem Rust • Leaf Rust • Stem Rust Pucciniatriticina Pucciniagraminisf. sp. tritici Photo courtesy of NCERA-184 & WERA-97

  5. Wheat Rust Obligate biotrophic fungus • Leaf Rust • Stem Rust • Stripe Rust Pucciniatriticina Pucciniagraminisf. sp. tritici Pucciniastriiformisf. sp. tritici Photo courtesy of NCERA-184 & WERA-97

  6. Breeding for Resistance • R-gene nomenclature • Leaf Rust: Lr • Stem Rust: Sr • Stripe (Yellow) Rust: Yr • R-genes confer resistance in a race-specific manner Lr21 Confers resistance to leaf rust race PRTUS6

  7. Suppression of stem rust resistance A B D • Stem rust-specific suppressor on Canthatch 7DL 1 Sr9 Sr16 2 3 Sr12 Sr7 4 7DL 5 Su 6 7

  8. Objective Investigate the specificity of the Canthatch suppressor Is it stem rust-specific? Is suppression related to genomes or chromosome locations?

  9. Objective • Investigate the stem rust specificity of the suppressor • Genetic characteristic of the suppressor • Absence of leaf rust or stripe rust resistance genes in the Canthatch background

  10. Approach

  11. Objective • Identify patterns of suppression related to genomes or chromosome locations

  12. Approach Genome Chromosome

  13. Control Crosses • Other suppressors in D genome (Bai & Knott, 1991) • Suppression may or may not be from our suppressor • Cross with mNS1-Can • If resistance is suppressed, it is not because of our suppressor • If resistance is expressed, it supports our hypothesis that it is because of our suppressor.

  14. Quantifying Infection Type Resis. Susc. Roelfs, A. & Singh, R. Rust diseases of wheat: Concepts and methods of disease management. 81 (Agribookstore/Winrock: 1992).

  15. Sample analysis

  16. SrX Canthatch x susuSrXSrX Su Su srxsrx All Resistant Su does not suppress SrX Screen F1 plants with race avirulent to SrX F1 plants: All Susceptible Su might suppress SrX Su suSrXsrx

  17. SrX mNS1-Can x susuSrXSrX sususrxsrx All Resistant There is no other gene suppressing expression of SrX in this background Screen F1 plants with race avirulent to SrX F1 plants: All Susceptible There is another suppressor in the background that suppresses SrX susuSrXsrx

  18. Statistical Analysis • Test 20 seeds • A significant difference 1/20 = 0.05 • Should be all resistant or all susceptible

  19. Crossing Log

  20. Sample Infection Type (IT) Data

  21. Alpowa SrX x Su SuSrXSrX sususrxsrx F1 plants: resistant SusuSrXsrx

  22. F1 plants: resistant Su suSrXsrx 9 : 3 : 3 : 1 F2 plants: Su__ SrX__ Su __ srxsrx susuSrX__ sususrxsrx ? resistant susceptible susceptible

  23. F1 plants: resistant Su suSrXsrx 9 : 3 : 3 : 1 F2 plants: Su__ SrX__ Su __ srxsrx susuSrX__ sususrxsrx resistant susceptible susceptible susceptible resistant 9 : 7 Alpowa suppressor suppresses SrX resistant : susceptible 3 : 1 Alpowa suppressor does not suppress SrX

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