13Impact on YieldSDS is correlated to the yield potential provided by the environmentPopular misconception that SDS does not cause yield lossYield loss occurs when infection occurs early in a high yielding environment (adequate rainfall), and symptoms are expressed at or near flowering.
15Environment SDS severity is increased with: Early planted fields Compacted soilHigh moisture, low soil temperature during vegetative growthCool period during floweringPresence of soybean cyst nematodeCrop rotations – inconsistent
16Impact of Planting Date Disease Index (DX)Date Rated
17Impact of Planting Date 2009 – SDS Variety Trials Valmeyer, IL planted 4/24Havana, IL planted 4/26Both fields have a history of SDS.
18Impact of Planting Date 2009 – SDS Variety Trials Carbondale, IL planted 5/20Paris, IL planted 5/29Both fields have a history of SDS, Carbondale was also infested with the pathogen.
19Chemical Control Current fungicides do not limit SDS in the field Some fungicides impact severity in greenhouse trialsHerbicides can reduce symptom severity in the fieldLactofen (X.B. Yang, Iowa State U.)Experimental productsGenerally, short lived reductionInduced resistance, affecting toxin movement or expression, ?
20Chemical ControlCould a product provide short-term protection to mirror that observed with delayed planting?Seed Care trials withScott Cully, Syngenta R&D- Havana and Valmeyer- Fungicide/Nematicide trts.
21Compacted Soils Vick et al. 2005. Canadian J. of Plant Path. 28:77-83. Vick et al Plant Dis. 87:
22Pathogen ResearchIdentification of fungal genes involved in the development of SDSKaryotyping (Chromosomal organization)SDS-SCN interactionA. Fakhoury, Southern Illinois U.
23Pathogen Research Generate REMI mutants ~800 mutants have been generated so farMutants screened for conidiation and growth patternGenerate and collaborate to generate sequence materialNecessary in identifying targets for disruptionExpedite gene disruptionPermits genomic and comparative genomic studies (complements karyotyping, population studies…)
24Tools Developed Optimize transformation system Optimize site directed mutagenesisA split-maker approach is being tested to disrupt genesSeveral genes are being targeted at this pointSnf1, grx, fsr1 and several kinasesA GFP expressing strain of the pathogen was produced
25ObjectivesIdentification of fungal genes involved in the development of SDSIdentification and characterization of pathways involved in virulence and pathogenesisDetection of the karyotypic variation among F. virguliforme isolates
26Karyotypic Variation Among Isolates F. virguliforme has 11 chromosomesWe estimate the size of the genome at ~ 33 MbpTested isolates exhibited polymorphism (differences) in terms of the sizes of their chromosomesThis polymorphism may be linked to the varying levels of aggressiveness exhibited by different isolates of the pathogenGTBM is Germ tube burst method. It is another way to visualize chromosomesMapping in the pathogenPolymorphism? What does it meanStress the fact that this is our dataChromosomes 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 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 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 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 Mbp.Nectria 40 MbpSoybean 1.1–1.15 GbHuman 750 MbpSCN 100MbpGTBM
27SDS interactions with SCN Synergistic –Roy et al., greenhouseMcLean and Lawrence, greenhouseRupe et al., 1991, field trialsHershman et al., 1990, field trialsXing and Westphal, 2006, microplotsAdditiveGao et al., greenhouse
30SDS and SCNSCN juvenile and mycelium of F. virguliforme
31Could Other Nematodes Be Involved? SDSRoot knot nematodeM. incognita
32Greenhouse trial Soybean cultivars were selected that differed for resistance to SCN, RKN, or SDSEach cultivar was challenged with the GFP- expressing virulent Fv transformant, the GFP- expressing avirulent Fv transformant, or several nematode/fungus co-inoculationsThe experiment consisted of 36 treatments replicated 5 times
34H. glycines M. incognita F. virguliforme R S Avirulent FvAvirulent Fv + SCNCultivarH. glycinesM. incognitaF. virguliformeForrestRP94M50SSpencerGH3983LS
35H. glycines M. incognita F. virguliforme R S Avirulent FvAvirulent Fv + SCNCultivarH. glycinesM. incognitaF. virguliformeForrestRP94M50SSpencerGH3983LS
36Host Resistance Quantitative resistance Controlled by multiple genes Difficult to test in the field
37Host 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 backcrossingB. DiersB. Diers and M. SchmidtB. Diers
38Evaluating Resistance to SDS Illinois Soybean AssociationSDS Commercial Variety TrialUSDA Uniform and Regional TrialsNorth Central Soybean Research ProgramNC Regional Trial
39Success equals ?A successful trial has a mean DX of at least 15 – 20 in susceptible check varieties.
40Factors That Insure Success Field with history of SDS and/or inoculation when neededEarly plantingIrrigationDisease evaluation at R6Appropriate check varietiesfor the maturity groupA good rating scale
41SDS Variety Trials Over 1,800 varieties (includes Public Lines) MG 1-5 Six locations overall3-4 for each MGOver 16,000 plotsResults distributed via , Websites, Mail, Popular press, Companies
42Variety Performance in 2009 Relative DXRatingPercentage of EntriesMGMG0-20Res.6521-40Mod. Res.1741-60Mod. Susc.233261+Susc.5446
43Greenhouse Assays Benefits/Limitations More art than science Agreement with known field reactionsHashmi obtained correlation of .80Collaborative university trials – Several blind trial competitions yielded correlationsHashmi et al Plant Health Progress doi: /PHP RS.
48Wish List Resistant commercial varieties and public germplasm Chemical treatments – seed, foliar, in-furrowFactors that contribute to severe diseaseIncreased resolution and consistency in field trialsMore efficient greenhouse/laboratory screening assays