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P lant pathology and disease resistance

P lant pathology and disease resistance. Who is Alison Robertson?. Who is Alison Robertson?. Who is Alison Robertson?. 1991 B.S. Plant Pathology Uni. of Kwazulu-Natal 1992-1999 Plant Pathologist Tobacco Research Board Zimbabwe

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P lant pathology and disease resistance

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  1. Plant pathology and disease resistance

  2. Who is Alison Robertson?

  3. Who is Alison Robertson?

  4. Who is Alison Robertson? 1991 B.S. Plant Pathology Uni. of Kwazulu-Natal 1992-1999 Plant Pathologist Tobacco Research Board Zimbabwe M.S. Plant Pathology University of Zimbabwe 2003 Ph.D. Plant Pathology Clemson University, SC

  5. Who is Alison Robertson? 2004 – present Associate professor/Extension field crops pathologist, Iowa State U. 70% extension; 30% research alisonr@iastate.edu alisonrISU

  6. Research Interests Goss’s wilt and leaf blight of corn

  7. Research Interests Seedling blights caused by Pythium

  8. Biology and management of Phytophthora sojae Alison Robertson

  9. Economic importance • Estimated yield loss due to Phytophthora root rot in US, 1996 to 2007 Wrather and Koenning. 2009. Plant Health Progress • 2003 - Iowa = 4 million bu; OH = 20.2 million bu Wrather and Koenning. 2006. J. Nematol.

  10. Phytophthora root and stem rot

  11. Management • Resistance • Single gene (Rps)  Rps1c, 1k or 3a • Partial resistance  multiple genes • Improve field drainage • Seed treatments

  12. Goal of research program 3. Seed treatments 1. Diversity Improve management systems to minimize losses due to PRR 4. Resistance 2. Molecular interactions i. Single gene ii. Partial resistance

  13. Soybean – P. sojae interaction Host Pathogen • There are 15 known resistant genes (Rps) in soybean • Disease is managed by deployment of cultivars with single gene resistance & partial resistance • Corresponding avirulence genes (Avr) in P. sojae • There are > 200 known pathotypes of this pathogen identified in standard 13 differential set (Dorrance, et al. 2003)

  14. Pathotyping

  15. Pathotyping 1a 1b 1c C 1d 1k 2 3a 7 3b 3c 4 5 6 8 Therefore pathotype = (1b,1c, 1k, 7)

  16. Identifying novel resistance genes

  17. Screening for partial resistance 2/3 vermiculite inoculum 1/3 vermiculite

  18. Mapping QTL for resistance PI399036 PI399036 Conrad Conrad AR2 Sloan AR3 Sloan

  19. BUT……P. sojae is extremely diverse

  20. P. sojaecontinues to evolve • In Iowa: • 1966-73: 1 pathotype (race 1; 7) • (Tachibana et al, 1975) • 1991-94: 11 pathotypes; race 3 predominant • (Yang et al, 1996) • 2001-02: 18 pathotypes; race 25 and 35 predominant (Niu, 2004) • 2005-2007: 11 races and 12 pathotypes not previously detected in the state(Robertson et al, 2009)

  21. Furthermore ………..

  22. Diversity in a single field - IA Robertson et al. 2009. Plant Health Progress

  23. Why is P. sojae so diverse? • Identify factors that shape the genetic diversity of xxxP. sojae populations

  24. SSRs • No. of SSRs highly variable between individuals • 25 SSRs identified in P. sojae (Dorrance and Grunwald, 2009; Schena et al, 2008)

  25. Evaluating population diversity

  26. 10 pathotypes 32 pathotypes 17 pathotypes

  27. Do Rps genes affect diversity of P. sojae? • H0 : Continuous use cultivars with specific Rpsgenes imposes selection pressure on the pathogen • Demonstrated for P. nicotianaeand tobacco system • (Sullivan et al., 2005)

  28. How do Rpsgenes affect diversity of P. sojae? Stewart and Robertson. 2014

  29. Number of pathotypes per treatment per year 1=S-S-S-S 2= S-R-S-R 3=R-PR-PR-R 4=R-R-R-R 5=PR-PR-PR-PR 6=R-R-R-R Stewart and Robertson. XXXX

  30. Number and pathotypes of P. sojae detected in rotation study R-R-R-R PR-PR-PR-PR R-R-R-R R-PR-PR-R S-R-S-R S-S-S-S Stewart and Robertson. XXXX

  31. How do Avrgenes evolve? • Characterize the genetic changes that occur within xxithe avirulence gene(s) of P. sojae that enable the xxipathogen to escape detection by the corresponding xxiresistant gene. Stewart et al. XXXX

  32. How does Avr change to escape detection by Rps?

  33. Other resources The links here are to two resources that I have been developing in collaboration with Don Lee at the University of Nebraska-Lincoln. The Oomycete Learning environment is primarily for agronomists and farmers but high school students should still learn something from it. The journey of a gene is an app we are developing for Future Farmers of America kids, so should be perfect for high schoolers. We welcome any feedback – positive and negative!. Thanks Oomycete Learning Environment (Phytophthora sojae) http://passel.unl.edu/communities/oomycete Journey of a gene http://passel.unl.edu/ge/

  34. Thanks for your attention.

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