title: Contributions of Fusarium virguliforme and Heterodera glycines to the disease complex of sudden death syndrome of soybean.
abstract: BACKGROUND
  Sudden death syndrome (SDS) of soybean caused by Fusarium virguliforme spreads and reduces soybean yields through the North Central region of the U.S. The fungal pathogen and Heterodera glycines are difficult to manage.
  
  
  RESULTS
  The objective was to determine the contributions of H. glycines and F. virguliforme to SDS severity and effects on soybean yield. To quantify DNA of F. virguliforme in soybean roots and soil, a specific real time qPCR assay was developed. The assay was used on materials from soybean field microplots that contained in a four-factor factorial-design: (i) untreated or methyl bromide-fumigated; (ii) non-infested or infested with F. virguliforme; (iii) non-infested or infested with H. glycines; (iv) natural precipitation or additional weekly watering. In years 2 and 3 of the trial, soil and watering treatments were maintained. Roots of soybean 'Williams 82' were collected for necrosis ratings at the full seed growth stage R6. Foliar symptoms of SDS (area under the disease progress curve, AUDPC), root necrosis, and seed yield parameters were related to population densities of H. glycines and the relative DNA concentrations of F. virguliforme in the roots and soil. The specific and sensitive real time qPCR was used. Data from microplots were introduced into models of AUDPC, root necrosis, and seed yield parameters with the frequency of H. glycines and F. virguliforme, and among each other. The models confirmed the close interrelationship of H. glycines with the development of SDS, and allowed for predictions of disease risk based on populations of these two pathogens in soil.
  
  
  CONCLUSIONS
  The results modeled the synergistic interaction between H. glycines and F. virguliforme quantitatively in previously infested field plots and explained previous findings of their interaction. Under these conditions, F. virguliforme was mildly aggressive and depended on infection of H. glycines to cause highly severe SDS.
authors.affiliation: Julius Kühn-Institut, Institute for Plant Protection in Field Crops and Grassland, Braunschweig, Germany; Department of Botany and Plant Pathology, Purdue University, West Lafayette, Indiana, United States of America.
authors.forename: Andreas
authors.initials: A
authors.lastname: Westphal
authors.affiliation: Department of Botany and Plant Pathology, Purdue University, West Lafayette, Indiana, United States of America; State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China.
authors.forename: Chunge
authors.initials: C
authors.lastname: Li
authors.affiliation: Department of Botany and Plant Pathology, Purdue University, West Lafayette, Indiana, United States of America; Marrone Bio Innovations Inc., Davis, California, United States of America.
authors.forename: Lijuan
authors.initials: L
authors.lastname: Xing
authors.affiliation: South Australian Research and Development Institute, Plant Research Centre, Urrbrae, South Australia, Australia.
authors.forename: Alan
authors.initials: A
authors.lastname: McKay
authors.affiliation: Department of Plant Pathology, University of Minnesota, St. Paul, Minnesota, United States of America.
authors.forename: Dean
authors.initials: D
authors.lastname: Malvick
mesh_terms: D000818:Animals; D060085:Coinfection; D004271:DNA, Fungal / Q000032:analysis; D005670:Fusarium / Q000235:genetics / Q000302:isolation & purification / Q000472:pathogenicity*; D010575:Pesticides; D010935:Plant Diseases / Q000382:microbiology* / Q000469:parasitology*; D018515:Plant Leaves / Q000382:microbiology; D018517:Plant Roots / Q000382:microbiology / Q000469:parasitology; D060888:Real-Time Polymerase Chain Reaction; D012680:Sensitivity and Specificity; D012987:Soil / Q000469:parasitology; D012988:Soil Microbiology; D013025:Glycine max / Q000382:microbiology* / Q000469:parasitology*; D013045:Species Specificity; D014431:Tylenchoidea / Q000302:isolation & purification / Q000472:pathogenicity*
chemical_list: D004271:DNA, Fungal; D010575:Pesticides; D012987:Soil