ARS Floral & Nursery Crops Research Initiative Research on Phytophthora spp. in South Carolina: Steven N. Jeffers Dept. of Plant Pathology & Physiology Clemson University Clemson, SC

Personnel Involved FFaculty VSteven N. Jeffers—Assoc. Prof. & Ext. Specialist VMelissa B. Riley—Associate Professor, Plant Path VDavid P. Jacobs--Professor, Computer Science FTechnicians VLynn Luszcz—Research Associate FGraduate Students VChun-hang Duan—Ph.D VJessica A. Eisenmann—M.S (expected)

Highlights of Accomplishments FPotential for rapid identification of Phytophthora spp. by Fatty Acid Methyl Ester (FAME) profile analysis FCharacterization of a population of Phytophthora cinnamomi associated with woody ornamental crops FCharacterization of populations of P. nicotianae & P. palmivora associated with herbaceous and selected woody ornamental crops FMaintain permanent culture collection

Peony—aerial blight Phlox—root rot Azalea—root rot Shore Juniper—root rot Floriculture CropsNursery Crops

Phytophthora spp. on Ornamental Crops FSerious problems in USA & worldwide FNumerous closely-related species involved FVarious sources of inoculum FAccurate identification essential Vextension—diagnosis & management Vresearch—etiology, ecology, epidemiology FStandard morphological identification Vnot always effective and accurate Vtime-consuming & labor-intensive

Why FAME Analysis ?? FProven technology—widely used for bacteria FUtilizes commercial hardware & software VMIDI System—Microbial Identification, Inc. FSystem present and used in many diagnostic labs worldwide FFAME profile database is electronic Veasily modified, shared, transferred F30 samples processed at one time FRelatively inexpensive

Objectives of Project FInvestigate effects of culture conditions on the production of fatty acids by selected species of Phytophthora FDevelop and standardize methods for generating fatty acid profiles for Phytophthora spp. FInvestigate variability in fatty acid profiles among these species

Dendrogram Based on FAME Analysis

FAME Identification: Summary FAmounts of each FA varied among species FFactors affecting FA production determined FStandard procedure for FAME analysis was developed FFAME profiles appear to be effective for identification of species FAFLP analysis supported FAME utility

FAME Identification: Future & Value FFuture Research Vconfirm utility with additional species Vconstruct FAME database with known isolates Vvalidate database with “unknown” isolates FValue of Research to Stakeholders Vprovide a rapid and inexpensive procedure for identification to diagnostic labs worldwide Vexpedite studies on management of Phytophthora diseases

Why Characterize Pathogen Populations ?? FDefine morphological & physiological characters Vaid in identification Vsensitivity to mefenoxam & other fungicides FOccurrence & distribution of mating types Vpotential for genetic variation & adaptation FPathogenicity & virulence Videntify new hosts, expand known host range Vdetermine relative virulence FUltimately—better disease management

Population of Phytophthora cinnamomi FPredominant species attacking nursery crops F51 isolates primarily from woody plants in SC Vrecovered between 1995 & 2000 by PP Clinic F49 isolates A2 & 2 isolates A1 FAll isolates sensitive to mefenoxam VEC 50 values: mg/L FAFLP analyses Visolates very similar genetically Vimplications for sources of inoculum…

Population of Phytophthora nicotianae FPredominant species attacking bedding plants, herbaceous perennials, Buxus spp. F108 isolates collected in SC during FBoth A1 & A2 mating types present VA2 most common FSome isolates resistant to mefenoxam VEC 50 values = mg/L F29 potentially new hosts under investigation FVirulence among isolates appears to differ

Potential “New” Hosts for P. nicotianae FAgapanthus FAruncus FCeratostigma plumbaginoides FDelosperma FGaura FHemerocallis FHibiscus syriacus FKniphofia FLamium FPenstemon FPetunia FPhlox paniculata FRodgersia FSalvia x superba FSedum FTiarella FVinca minor FViola x wittrockiana

New hosts for P. nicotianae Sedum—root rot Petunia—root rot

Population of Phytophthora palmivora FPreviously not found on ornamental crops in the Southeast FPrimarily attacks Hedera spp. & Fatsia japonica Vboth in the family Araliaceae F38 isolates collected in SC during FMorphologically similar to P. nicotianae FOnly A1 mating type found FAll isolates very sensitive to mefenoxam VEC 50 values < 0.10 mg/L

Pathogen Populations: Future & Value FFuture Research Vcompare populations from ornamental crops to those from natural ecosystems Vdetermine virulence of isolates from different populations Videntify sources of primary inoculum FValue to Stakeholders Videntify new host species Vpinpoint sources of inoculum Vmore effective disease management strategies

Phytophthora Culture Collection FMaintain a collection of isolates Vvaluable resource Vdistribute isolates to colleagues Vreceive isolates from colleagues FConstructing an ACCESS database so information is readily accessible Vin cooperation with Dept. of Computer Science Vwill be posted on the web