Upload
malorie-scholz
View
27
Download
1
Embed Size (px)
DESCRIPTION
P lant pathology and disease resistance. Who is Alison Robertson?. Who is Alison Robertson?. Who is Alison Robertson?. 1991B.S. Plant Pathology Uni. of Kwazulu-Natal 1992-1999 Plant Pathologist Tobacco Research Board Zimbabwe - PowerPoint PPT Presentation
Citation preview
Plant 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
1999 M.S. Plant Pathology University of Zimbabwe
2003 Ph.D. Plant Pathology Clemson University, SC
Who is Alison Robertson?2004 – presentAssociate professor/Extension field crops pathologist, Iowa State U.
70% extension; 30% research
[email protected] alisonrISU
Research InterestsGoss’s wilt and leaf blight of corn
Research InterestsSeedling blights caused by Pythium
Biology and management of Phytophthora sojae
Alison Robertson
Economic importance
• Estimated yield loss due to Phytophthora root rot in US, 1996 to 2007
19961998
20002002
20042006
010,00020,00030,00040,00050,00060,000
1000
bus
hels
Wrather and Koenning. 2009. Plant Health Progress
• 2003 - Iowa = 4 million bu; OH = 20.2 million buWrather and Koenning. 2006. J. Nematol.
Phytophthora root and stem rot
Resistance― Single gene (Rps) Rps1c, 1k or 3a― Partial resistance multiple genes
Improve field drainage
Seed treatments
Management
Goal of research program
Improve management systems to minimize losses due to PRR
3. Seed treatments1. Diversity
2. Molecular interactions 4. Resistance
i. Single gene ii. Partial resistance
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)
Host Pathogen
Soybean – P. sojae interaction
Pathotyping
Therefore pathotype = (1b,1c, 1k, 7)
1a 1b 1c 1k 2 3a
3b 3c 4 5 6 7 8
1d C
Pathotyping
Identifying novel resistance genes
Screening for partial resistance
1/3 vermiculite
inoculum
2/3 vermiculite
AR2
AR3
PI39
9036
Conr
ad
Sloa
n Sloa
n
PI39
9036
Conr
ad
Mapping QTL for resistance
BUT……P. sojae is extremely diverse
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)
P. sojae continues to evolve
Furthermore ………..
Robertson et al. 2009. Plant Health Progress
Diversity in a single field - IA
Identify factors that shape the genetic diversity of xxxP. sojae populations
Why is P. sojae so diverse?
No. of SSRs highly variable between individuals
25 SSRs identified in P. sojae (Dorrance and Grunwald, 2009; Schena et al, 2008)
SSRs
Evaluating population diversity
R14R17
R2R25
Iowa Ohio South Dakota Checks
Coord. 1
Coor
d. 2
10 pathotypes 32 pathotypes 17 pathotypes
H0 : Continuous use cultivars with specific Rps genes imposes selection pressure on the pathogen
Demonstrated for P. nicotianae and tobacco system(Sullivan et al.,
2005)
Do Rps genes affect diversity of P. sojae?
Year Treatment1 2 3 4 5 6
2007 Susceptible Susceptible Rps1k Rps1k Partial R Rps1k2008 Susceptible Rps1k Partial R Rps1c Partial R Rps1k2009 Susceptible Susceptible Partial R Rps3a Partial R Rps1k2010 Susceptible Rps1k Rps1k Rps1k Partial R Rps1k
How do Rps genes affect diversity of P. sojae?
Stewart and Robertson. 2014
Number of pathotypes per treatment per year
1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6planting harvest planting harvest planting harvest planting
2007 2008 2009 2010
0
2
4
6
8
10
12
race 1 others
Treatments
No.
isola
tes
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-RStewart and Robertson. XXXX
Number and pathotypes of P. sojae detected in rotation study
Stewart and Robertson. XXXX
S-S-S-S
R-R-R-R
PR-PR-PR-PR
S-R-S-R
R-R-R-R
R-PR-PR-R
How do Avr genes evolve?
Stewart et al. XXXX
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.
How does Avr change to escape detection by Rps?
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 genehttp://passel.unl.edu/ge/
Thanks for your attention.