Sudden Death Syndrome of Soybean Dr. Jason Bond, Plant Pathologist Southern Illinois University jbond@siu.edu 618-453-4309

Sudden Death Syndrome Disease and Impact Pathogen Biology Cultural Management Host Resistance

Yield Losses – Northern US Disease 3-year average (bu in millions) Soybean cyst nematode 122.4 Phytophthora rot 42.1 Seedling diseases 41.1 Sudden death syndrome 22.7 Charcoal rot 17.6 Brown spot 16.2 Brown stem rot 14.1 Anthracnose 11.3 Sclerotinia stem rot 10.0 Frogeye leaf spot 7.6 Fusarium root rot Source: Allan Wrather, UM, Portageville, MO

Fusarium virguliforme (= F. solani f. sp. glycines) Soilborne, root rotting fungus that colonizes tap root and crown Produces a toxin(s) Foliar symptoms generally start at R2 in field

Symptoms

Similar Foliar Symptoms Stem Canker Phytophthora stem rot

Similar Foliar Symptoms Brown Stem Rot SDS

Spread of SDS 1993 2002 1997 2005? 2000 1993 1999 2004 1997 1986 2000 1984 1992 1986 1984 1997 1986 1971 1984 1984 1997 1997 1986

Rating Foliar Symptoms Disease Incidence (DI) - % of plants in the plot showing leaf symptoms. Disease Severity (DS) - Severity of diseased plants scored on a 1-9 scale. Disease Index (DX) = (DI*DS)/9

DX 25 - 30

DX 50 - 60

DX 60 - 75

Impact on Yield SDS is correlated to the yield potential provided by the environment Popular misconception that SDS does not cause yield loss Yield loss occurs when infection occurs early in a high yielding environment (adequate rainfall), and symptoms are expressed at or near flowering.

Impact on Yield

Environment SDS severity is increased with: Early planted fields Compacted soil High moisture, low soil temperature during vegetative growth Cool period during flowering Presence of soybean cyst nematode Crop rotations – inconsistent

Impact of Planting Date Disease Index (DX) Date Rated

Impact of Planting Date 2009 – SDS Variety Trials Valmeyer, IL planted 4/24 Havana, IL planted 4/26 Both fields have a history of SDS.

Impact of Planting Date 2009 – SDS Variety Trials Carbondale, IL planted 5/20 Paris, IL planted 5/29 Both fields have a history of SDS, Carbondale was also infested with the pathogen.

Chemical Control Current fungicides do not limit SDS in the field Some fungicides impact severity in greenhouse trials Herbicides can reduce symptom severity in the field Lactofen (X.B. Yang, Iowa State U.) Experimental products Generally, short lived reduction Induced resistance, affecting toxin movement or expression, ?

Chemical Control Could a product provide short-term protection to mirror that observed with delayed planting? - 2010 Seed Care trials with Scott Cully, Syngenta R&D - Havana and Valmeyer - Fungicide/Nematicide trts.

Compacted Soils Vick et al. 2005. Canadian J. of Plant Path. 28:77-83. Vick et al. 2003. Plant Dis. 87:629-632.

Pathogen Research Identification of fungal genes involved in the development of SDS Karyotyping (Chromosomal organization) SDS-SCN interaction A. Fakhoury, Southern Illinois U.

Pathogen Research Generate REMI mutants ~800 mutants have been generated so far Mutants screened for conidiation and growth pattern Generate and collaborate to generate sequence material Necessary in identifying targets for disruption Expedite gene disruption Permits genomic and comparative genomic studies (complements karyotyping, population studies…)

Tools Developed Optimize transformation system Optimize site directed mutagenesis A split-maker approach is being tested to disrupt genes Several genes are being targeted at this point Snf1, grx, fsr1 and several kinases A GFP expressing strain of the pathogen was produced

Objectives Identification of fungal genes involved in the development of SDS Identification and characterization of pathways involved in virulence and pathogenesis Detection of the karyotypic variation among F. virguliforme isolates

Karyotypic Variation Among Isolates F. virguliforme has 11 chromosomes We estimate the size of the genome at ~ 33 Mbp Tested isolates exhibited polymorphism (differences) in terms of the sizes of their chromosomes This polymorphism may be linked to the varying levels of aggressiveness exhibited by different isolates of the pathogen GTBM is Germ tube burst method. It is another way to visualize chromosomes Mapping in the pathogen Polymorphism? What does it mean Stress the fact that this is our data Chromosomes of each of the F. virguliforme isolates, Iowa07, Carmi07, Mont-1, ARC07, AF06 and Vick07 were separated by PFGE. A combination of two different electrophoresis conditions were optimized and used to separate and resolve fungal chromosomes. The size and number of the separated chromosomes were determined based on the assumption that there is a linear relationship between chromosome size and migration distance on the gel. PFGE performed under conditions optimized for the separation of small to medium size chromosomes revealed five bands for each isolate ranging in size between 0.8-2.2 Mbp. Two of these bands, with estimated sizes of 1.6 and 2.2 Mbp, were present in all the isolates included in this study (FIG. 1). One band, with an estimated size of 0.8Mbp and two bands with estimated sizes of 1.2 and 1.3 Mbp were resolved in isolates Vick07, Carmi07, ARC07 and AF06. Three bands ranging in size between 1.1-1.4 Mbp were resolved exclusively in the isolates Mont1 and Iowa07. Under conditions optimized for the separation of large chromosomes, four chromosomes in the size range 3.2-5.7 Mbp were observed for all isolates in this study (FIG. 2). PFGE data for all chromosomes identified is compiled in FIG 3. PFGE revealed that F. virguliforme isolates have nine chromosomes and an estimated genome size of 24.6-25.2 Mbp. Nectria 40 Mbp Soybean 1.1–1.15 Gb Human 750 Mbp SCN 100Mbp GTBM

SDS interactions with SCN Synergistic – Roy et al., 1989- greenhouse McLean and Lawrence, 1993 - greenhouse Rupe et al., 1991, field trials Hershman et al., 1990, field trials Xing and Westphal, 2006, microplots Additive Gao et al., 2006 - greenhouse

Distribution of SCN Source: G. Tylka, ISU

SDS and SCN

SDS and SCN SCN juvenile and mycelium of F. virguliforme

Could Other Nematodes Be Involved? SDS Root knot nematode M. incognita

Greenhouse trial  Soybean cultivars were selected that differed for resistance to SCN, RKN, or SDS Each cultivar was challenged with the GFP- expressing virulent Fv transformant, the GFP- expressing avirulent Fv transformant, or several nematode/fungus co-inoculations The experiment consisted of 36 treatments replicated 5 times

Cultivar H. glycines M. incognita F. virguliforme Forrest R P94M50 S Spencer GH3983 LS97-1610

H. glycines M. incognita F. virguliforme R S Avirulent Fv Avirulent Fv + SCN Cultivar H. glycines M. incognita F. virguliforme Forrest R P94M50 S Spencer GH3983 LS97-1610

H. glycines M. incognita F. virguliforme R S Avirulent Fv Avirulent Fv + SCN Cultivar H. glycines M. incognita F. virguliforme Forrest R P94M50 S Spencer GH3983 LS97-1610

Host Resistance Quantitative resistance Controlled by multiple genes Difficult to test in the field

Host Resistance Mapped genes from PI 567374 in greenhouse. Genes on linkage group D2 and I. Mapped genes from Ripley in field with SSR markers using field data. Genes on linkage group D2 and L. Genes have been confirmed and are conducting marker-assisted backcrossing B. Diers B. Diers and M. Schmidt B. Diers

Evaluating Resistance to SDS Illinois Soybean Association SDS Commercial Variety Trial USDA Uniform and Regional Trials North Central Soybean Research Program NC Regional Trial

Success equals ? A successful trial has a mean DX of at least 15 – 20 in susceptible check varieties.

Factors That Insure Success Field with history of SDS and/or inoculation when needed Early planting Irrigation Disease evaluation at R6 Appropriate check varieties for the maturity group A good rating scale

SDS Variety Trials Over 1,800 varieties (includes Public Lines) MG 1-5 Six locations overall 3-4 for each MG Over 16,000 plots Results distributed via Email, Websites, Mail, Popular press, Companies www.soybeandiseases.info www.vipsoybeans.org www.soybean.siu.edu

Variety Performance in 2009 Relative DX Rating Percentage of Entries MG 1 - 3.4 MG 3.5 - 5.0 0-20 Res. 6 5 21-40 Mod. Res. 17 41-60 Mod. Susc. 23 32 61+ Susc. 54 46

Greenhouse Assays Benefits/Limitations More art than science Agreement with known field reactions Hashmi obtained correlation of .80 Collaborative university trials – Several blind trial competitions yielded correlations 0 - .59 Hashmi et al. 2005. Plant Health Progress doi:10.1094/PHP-2005-0906-01-RS.

Waterbath Method

Tray Method Pictures – R. Bowen, UIUC

Pictures – R. Bowen, Univ. of Illinois 1 –Typical plant, showing no symptoms. 3 – Leaf with obvious, inter-veinal chlorosis Pictures – R. Bowen, Univ. of Illinois

Pictures – R. Bowen, UIUC

Wish List Resistant commercial varieties and public germplasm Chemical treatments – seed, foliar, in-furrow Factors that contribute to severe disease Increased resolution and consistency in field trials More efficient greenhouse/laboratory screening assays

Summary

Questions? Jason P. Bond jbond@siu.edu 618-453-4309