title: Soybean sudden death syndrome species diversity within north and South america revealed by multilocus genotyping.
abstract: Sudden death syndrome (SDS) of soybean has become a serious constraint to the production of this crop in North and South America. Phenotypic and multilocus molecular phylogenetic analyses, as well as pathogenicity experiments, have demonstrated that four morphologically and phylogenetically distinct fusaria can induce soybean SDS. Published molecular diagnostic assays for the detection and identification of these pathogens have reported these pathogens as F. solani, F. solani f. sp. glycines, or F. solani f. sp. phaseoli, primarily because the species limits of these four pathogens were only recently resolved. In light of the recent discovery that soybean SDS and Phaseolus and mung bean root rot (BRR) are caused by four and two distinct species, respectively, multilocus DNA sequence analyses were conducted to assess whether any of the published molecular diagnostic assays were species-specific. Comparative DNA sequence analyses of the soybean SDS and BRR pathogens revealed that highly conserved regions of three loci were used in the design of these assays, and therefore none were species-specific based on our current understanding of species limits within the SDS-BRR clade. Prompted by this finding, we developed a high-throughput multilocus genotyping (MLGT) assay which accurately differentiated the soybean SDS and two closely related Phaseolus and mung BRR pathogens based on nucleotide polymorphism within the nuclear ribosomal intergenic spacer region rDNA and two anonymous intergenic regions designated locus 51 and 96. The single-well diagnostic assay, employing flow cytometry and a novel fluorescent microsphere array, was validated by independent multilocus molecular phylogenetic analysis of a 65 isolate design panel. The MLGT assay was used to reproducibly type a total of 262 soybean SDS and 9 BRR pathogens. The validated MLGT array provides a unique molecular diagnostic for the accurate identification and molecular surveillance of these economically important plant pathogens.
authors.affiliation: Microbial Genomics Research Unit, National Center for Agricultural Utilization Research , Us Department of Agriculture, Agriculture research Service, Peoria, IL 61604, USA. kerry.odonnell@ars.usda.gov
authors.forename: Kerry
authors.initials: K
authors.lastname: O'Donnell
authors.forename: Stacy
authors.initials: S
authors.lastname: Sink
authors.forename: María Mercedes
authors.initials: MM
authors.lastname: Scandiani
authors.forename: Alicia
authors.initials: A
authors.lastname: Luque
authors.forename: Analía
authors.initials: A
authors.lastname: Colletto
authors.forename: Marisa
authors.initials: M
authors.lastname: Biasoli
authors.forename: Lisandro
authors.initials: L
authors.lastname: Lenzi
authors.forename: Graciela
authors.initials: G
authors.lastname: Salas
authors.forename: Victoria
authors.initials: V
authors.lastname: González
authors.forename: Leonardo Daniel
authors.initials: LD
authors.lastname: Ploper
authors.forename: Norma
authors.initials: N
authors.lastname: Formento
authors.forename: Rosanna N
authors.initials: RN
authors.lastname: Pioli
authors.forename: Takayuki
authors.initials: T
authors.lastname: Aoki
authors.forename: X B
authors.initials: XB
authors.lastname: Yang
authors.forename: Brice A J
authors.initials: BA
authors.lastname: Sarver
mesh_terms: D044822:Biodiversity; D004271:DNA, Fungal / Q000235:genetics*; D021903:DNA, Ribosomal Spacer / Q000235:genetics; D005670:Fusarium / Q000145:classification / Q000235:genetics*; D005838:Genotype; D009656:North America; D010802:Phylogeny; D010935:Plant Diseases / Q000382:microbiology*; D016133:Polymerase Chain Reaction; D013020:South America; D013025:Glycine max / Q000382:microbiology*
chemical_list: D004271:DNA, Fungal; D021903:DNA, Ribosomal Spacer