Biotic pests in cereal crop production: plant pathogens

Wheat streak mosaic virus and Stem Rust Ug99

Mary Burrows, Dai Ito, Matt Moffet, Zach Miller, Fabian Menalled, Mareike Johnston, Luther Talbert,

Tom Blake, and Phil Bruckner

• Initiated in 2002 by USDA-CSREES with homeland security funding

• Goal: to provide diagnostic capability to the nation’s agricultural system

• Five regional hubs with responsibility for diagnostics, funding, public relations, epidemiology, and training

Regional Networks of NPDNRegional Networks of NPDN

Western Plant Diagnostic NetworkUniversity of California, Davis

Great Plains Diagnostic Network

Kansas State University

South Eastern Plant Diagnostic NetworkUniversity of Florida

North Central Plant Diagnostic Network

Michigan State University

North Eastern Plant Diagnostic NetworkCornell University

National AgriculturalPest Information System

Purdue University

Network ResponsibilitiesNetwork Responsibilities• Data collection (detectors/diagnosticians)• Communications system• Information storage and management• Data analysis

• New events and analysis of new appearance• Pattern recognition• Unusual patterns of endemic problems

• GIS• Event propagation• Tracking

• Reporting and alerts• Link to State Departments of Ag and US regulatory • agencies

WSMV: The Pathogen

• Family Potyviridae, genus Tritimovirus

• Mite-transmitted virus

Wheat streak mosaic virus• Infects both winter and spring wheat

– Symptoms in spring

• Earlier infection = greater yield loss• Grassy weeds, volunteer wheat, corn, etc.

can harbor both WSMV and the mite vector• 5-10% yield loss/yr across Great Plains• 100% yield loss in individual fields

SDSU Extension

Disease cycle of WSMV

Table 2. Capacity of prevalent grassy weeds in Montana to serve as mite and virus hosts.*Common name Scientific name Life cycle Mite host WSMV hostJointed goatgrass Aegilops cylindricae Annual Yes YesCrested wheatgrass Agropyron cristatum Perennial Unknown UnknownWild oat Avena fatua Annual No YesSmooth brome Bromus inermis Perennial Yes NoJapanese brome Bromus japonicus Perennial No UnknownDowny brome/Cheatgrass Bromus tectorum Annual Yes YesPersian darnell Lolium persicum Annual Unknown UnknownWestern wheatgrass Pascopyrum smithii Perennial Yes NoFeral rye Secale cereale Annual Unknown UnknownYellow foxtail Setaria glauca Annual No NoGreen foxtail Setaria viridis Annual Yes Yes*data taken from literature cited in text

Weed Host: Volunteer Wheat

WSMV in Montana weeds, 2008

Plant Ft.Benton Conrad site 1 Conrad site 2Wheat (in crop field) 68/100 42/100 66/ 100Crested wheatgrass 0/25 0/25 0/25Downy Brome N/ A 6/100 0/25Foxtail 0/25 0/25 0/25Wild oat 0/25 0/50 1/25Volunteer wheat 4/50 7/50

Volunteer wheat is the best non-crop host, but weed species are also are infected with virus and may serve as a source

Which weeds are susceptible?Which weeds are susceptible?

Common nameLiteratur

e1 ELISA2

Jointed goatgrass Yes LocalWild oat Yes +Downy Brome Yes LocalCrested Wheatgrass

No -

Thickspike Wheatgrass No -Quackgrass No +Slender Wheatgrass

No -

Smooth Brome No -Barnyardgrass Yes +Green Foxtail Yes -1WSMV host data taken from Somsen 1970, Townsend 1996, and Brey, 1998.2Data from MSU: 'Local' = Virus restricted to inoculated leaves in preliminary assay

Regional variation in the susceptibility of weeds to WSMV

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

Downy brome Green Foxtail Jointed goatgrass Quackgrass Wild oat

α-W

SMV

ELIS

A ab

sorb

ance

rel

ative

to in

fect

ed w

heat

(w

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whe

at =

1)

ColoradoIdahoMontanaNebraskaOklahoma

Figure 1. Susceptibility of grassy weed species in five Great Plains states to Wheat streak mosaic virus (WSMV) as measured by ELISA of mechanically inoculated plants.

Wheat = 1

Increase in regional virus incidence?

Host

Pathogen Environment（ New York Times)

SDSU Extension

Vector

• Determine prevalence of wheat viruses in the Great Determine prevalence of wheat viruses in the Great Plains (Plains (WSMV, HPV, TriMV, BYDV-PAV and CYDV-WSMV, HPV, TriMV, BYDV-PAV and CYDV-RPVRPV))

• Nine states: Nine states: WY, MT, CO, KS, OK, TX, SD, ND, NE

• Determine geographic distribution for TriMV & HPVDetermine geographic distribution for TriMV & HPV

• Determine if host symptoms are diagnostic among virus Determine if host symptoms are diagnostic among virus species for single and multiple infectionsspecies for single and multiple infections

• Collect and provide virus infected plant tissues to support Collect and provide virus infected plant tissues to support research effortsresearch efforts

• Increase communication about wheat viruses in the Great Increase communication about wheat viruses in the Great Plains RegionPlains Region

Wheat virus survey, 2008: Objectives

ObjectiveObjective: : Determine prevalence of wheat viruses

• WSMV detected in all GPDN states at WSMV detected in all GPDN states at high percentage infection (10 – 83 %)high percentage infection (10 – 83 %)

• HPV detected in all GPDN statesHPV detected in all GPDN states• HPV identified in MT and WY for the first HPV identified in MT and WY for the first

timetime• TriMV identified in all states, all but KS TriMV identified in all states, all but KS

new reportsnew reports

2008 n WSMV WMoV TriMVColorado 51 61 10 10Kansas 53 62 38 30Montana 23 43 9 0Nebraska 66 39 8 27North Dakota 44 40 12 0Oklahoma 93 27 30 6South Dakota 96 28 7 2Texas 307 83 41 57Wyoming 21 38 19 24Total 754 47 19 17

2009Colorado 145 50 24 21Kansas 62 14 0 2Montana 150 29 4 7Nebraska 100 14 16 44North Dakota 92 52 12 .Oklahoma 77 49 17 18South Dakota 44 27 14 .Texas 322 44 4 14Wyoming 21 10 19 0Total 1013 32 12 20

2008 n WSMV + WMoV WSMV + TriMV WMoV + TriMV All miteColorado 51 8 8 0 0Kansas 53 15 21 13 8Montana 23 9 0 0 0Nebraska 66 8 18 5 5North Dakota 44 9 0 0 0Oklahoma 93 16 4 3 3South Dakota 96 7 2 1 1Texas 307 37 53 28 26Wyoming 21 5 10 10 0Total 754 13 13 13 5

2009Colorado 145 70 67 46 6Kansas 62 14 16 2 0Montana 150 3 5 1 1Nebraska 100 31 57 60 3North Dakota 92 63 . . .Oklahoma 77 66 68 36 0South Dakota 44 41 . . .Texas 322 48 58 18 2Wyoming 21 76 14 10 0Total 1013 46 46 29 2

Winter wheat: inoculated trials

Winter wheat: inoculated trials

Yield reductions due to spring inoculation with WSMV, 2008 & 2009

2008 2009

VarietyYield of control

(bu/a)% yield

reductionYield of control

(bu/a)% yield

reduction

Genou 42.4 24.8 91.4 15.2

CDC Falcon 38.3 -25.1 79.0 18.3

Rampart 45.4 15.6 84.8 15.8

Neeley 35.9 42.6 111.8 34.9

Ledgar 48.5 -31.2 81.3 8.2

Jagalene 37.7 10.3 64.9 0.1

Tiber 32.1 40.9 94.6 26.6

Yellowstone 40.1 13.7 118.3 22.6

Rocky 28.6 19.0 79.5 19.6

Pryor 45.9 -14.4 108.6 14.7

Morgan 38.2 24.2 90.2 23.0

MTV0734 41.6 37.1 78.6 19.7

Average 39.56 13.11 90.26 18.2

Spring wheat: inoculated trials

Spring wheat: inoculated trials

Yield reductions due to inoculation with WSMV, 2008 & 2009

2008 2009

VarietyYield of control

(bu/A)% yield

reductionYield of control

(bu/A)% yield

reduction

Reeder 17.7 22.8 67.8 34.2

Choteau 28.5 33.6 60.0 51.9

McNeal 25.5 39.9 60.5 50.4

Conan 25.3 24.2 56.3 32.5

Fortuna 21.0 32.7 52.9 42.2

Ernest 18.5 34.7 64.8 57.3

Corbin 24.4 18.0 56.2 31.9

Hank 31.9 21.8 61.7 28.4

Amidon 11.5 8.8 71.1 38.7

Scholar 18.2 45.9 61.8 44.3

Metcalfe N/A N/A 96.1 16.7

Haxby N/A N/A 98.4 13.3

Mean 22.2 28.2 67.3 36.8

Race Evolution in TTKS (Ug99) Lineage

&

Implications to Resistance Breeding

Yue Jin, USDA-ARS

Ug99

First reported in Uganda in 1999

--Pretorius et al. 2000 Plant Dis 84:203

Virulent on Sr31

Sr31 is located on 1BL.1RS translocationAlso carries Lr26, Yr9Increased adaptation and higher yield. As a result,

widely spread in wheat worldwideHelped to reduce stem rust population worldwide

Virulence to Yr9, originated in the eastern Africa in mid 80s, caused worldwide epidemics

TTKS

In 2002 and 2004, CIMMYT nursery planted in Njoro, Kenya were severely infected by stem rust.

In 2005, we identified Kenyan isolates from 2004 were race TTKS.

--Wanyera, Kinyua, Jin, Singh 2006 Plant Dis 90:113

Broad virulence of TTKS to North American spring wheat

US spring wheat CVs of the Northern Great Plains, known to have broad-based resistance to stem rust, were mostly susceptible (84%).

500 CIMMYT CVs released since 1950’s, 84% were susceptible.

Conclusion:

Ug99 possesses a unique virulence combination that renders many resistance genes ineffective.

Jin & Singh, 2006, Plant Dis:90:476-480

Evolution of the TTKS lineage

TTKSK

TTTSKTTKST

Sr24-Sr31+Sr36-

Sr24+Sr31+Sr36-

Sr24-Sr31+Sr36+

Our data point to:

Jin et al. 2008. Plant Dis. 92:923-926Jin et al. 2009. Plant Dis. (in Press)

% of resistance to

Type Entry TTKSK TTKST TTTSK(Ug99) Sr24v Sr36v

Hard red spring 89 21% 12% 21%

Hard red winter 416 29% 15% 28%

Soft red winter 377 27% 25% 11%

Western wheat 60 3% 3% 3%

Total 942 26% 18% 19%

Ramification of Sr24/Sr36 virulence to US Wheatbased on testing of 2007 elite breeding germplasm

Current status of Ug99• New races constantly evolving• Ug99 stalled in Iran due to long drought• If moves to Pakistan/India will affect 15% of

world’s wheat crop that feeds 1 billion of the world’s poorest people

• Strain of stem rust in India that overcomes Sr25• ‘Likely’ Ug99 has already spread beyond Iran -

Rick Ward, co-coordinator of the Durable Rust Resistance in Wheat project, based at Cornell university; http://rustopedia.org/traction/permalink/Resources905

Projected potential pathways for Ug99 based on the migration of Yr9 virulence

Singh et al. 2006. CAB Review 1, 54

Ug99 migration

Singh et al. 2008. Advances in Agronomy v981998 2001?

2004

2003?2005

2006

2006

2007

The good news

• Phil and Luther are both working on it already!

• Li Huang, PSPP, has identified spring wheat mutants from a population derived by Mike Giroux with resistance to leaf, stem, and stripe rust – including all Ug99 derivatives

• Fungicide trials with great results• Communication and education ramping up!

Wheat stem rust fungicide trial results (2008)Stein and Gupta, SDSU

Ste

m r

ust (

% le

af a

rea)

TriazolesTriazole + Strobilurin

Fungicide modes of action: Triazoles• FRAC group 3• DMI (demethylation) inhibitors; biosynthesis of sterols in

fungal cell membrane; spore penetration and mycelial growth

• Provides 14-21 days of protection• Medium risk of resistance development• Greater mobility in plant than strobilurin fungicides• Most widely used class of fungicide in the world• Control a wide array of fungal diseases• Protective and curative effects (if applied early in disease

development)

Fungicide movement in the plant

From: Tenuta, A., D. Hershman, M. Draper and A. Dorrence. 2007. Using foliar fungicides to manage soybean rust.. Land-Grant Universities Cooperating NCERA-208 and OMAF. Available online at http://www.oardc.ohio-state.edu/SoyRust/

Fungicide modes of action: Strobilurins

• FRAC group 11• QoI (quinone outside) inhibitors (respiration); spore germination,

penetration, and mycelial growth• Provides 14-21 days of protection• High risk of resistance development because it has a very

specific mode of action (they block electron transfer at the site of quinol oxidation (the Qo site) in the cytochrome bc1 complex, thus preventing ATP formation)

• Originally isolated from wood-rotting fungi Strobilurus tenacellus• ‘Reduced-risk’ pesticide (pose less risk to human health than

other chemical options at the time of registration by EPA)• Control a wide array of fungal diseases• Excellent preventative fungicides, but limited curative effects• “Plant health benefit” independent of disease control?

Figure 1. Mobility of trifloxystrobin, an example of a QoI fungicide. http://www.apsnet.org/education/AdvancedPlantPath/Topics/Strobilurin/top.htm

Preventing fungicide resistance

• Limit the number of applications of a single FRAC group per season

• Limit the number of consecutive applications of a single FRAC group

• Mix fungicides with different modes of action (FRAC groups)

• Use early in disease development

Stem rust fungicide trial

Rate Active Ingredient Company1.Control2.Proline 480 SC 5.3 oz Prothioconazole Bayer3. Prosaro 421 SC 7.5 oz Tebuconazole + Prothioconazole Bayer4. Quilt 14 oz Azoxystrobin + Propiconazole Syngenta5. A15590C 14 oz Azoxystrobin + Propiconazole Syngenta6. Alto 100SL 4 oz Cyproconazole Syngenta7. Caramba 13.5 oz Metconazole BASF8. Twinline 9 oz Pyraclostrobin +Metconazole BASF9. Headline 2.09EC 7.5 oz Pyraclostrobin BASF10. Gem 500 SC 2.4 oz Trifloxystrobin Bayer

Control (no fungicide), 14 daa

Strobilurin fungicides, 14 daa

Headline

Gem 500 SC

Strobiliurin + Trizole, 14 daa

QuiltQuilt Xcel

Strobiliurin + Trizole, 14 daa

Prosaro

Twinline

Trizole fungicides, 14 daa

Alto

Proline

Caramba

Compare sprayed and unsprayed plots

Yield, stem rust fungicide trial2009, Bozeman

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