# Presentation: 003360

## ARS Floral & Nursery Crops Research InitiativeResearch on Phytophthora spp.in South Carolina: 2000-2003

**ARS Floral & Nursery Crops Research Initiative****Research on *****Phytophthora***** spp.****in South Carolina: 2000-2003**

**Steven N. Jeffers**
- Dept. of Plant Pathology & Physiology
- Clemson University
- Clemson, SC

## Personnel Involved

- Faculty
- Steven N. Jeffers—Assoc. Prof. & Ext. Specialist
- Melissa B. Riley—Associate Professor, Plant Path
- David P. Jacobs--Professor, Computer Science
- Technicians
- Lynn Luszcz—Research Associate
- Graduate Students
- Chun-hang Duan—Ph.D. 2002
- Jessica A. Eisenmann—M.S. 2003 (expected)

## Highlights of Accomplishments

- Potential for rapid identification of *Phytophthora* spp. by **F**atty **A**cid **M**ethyl **E**ster (FAME) profile analysis
- Characterization of a population of *Phytophthora   cinnamomi* associated with woody ornamental crops
- Characterization of populations of *P. nicotianae* & *P. palmivora *associated with herbaceous and selected woody ornamental crops
- Maintain permanent culture collection

## Floriculture Crops

- Nursery Crops

## Phytophthora spp. onOrnamental Crops

- Serious problems in USA & worldwide
- Numerous closely-related species involved
- Various sources of inoculum
- Accurate identification essential
- extension—diagnosis & management
- research—etiology, ecology, epidemiology
- Standard morphological identification
- not always effective and accurate
- time-consuming & labor-intensive

## Why FAME Analysis ??

- Proven technology—widely used for bacteria
- Utilizes commercial hardware & software
- MIDI System—Microbial Identification, Inc.
- System present and used in many diagnostic labs worldwide
- FAME profile database is electronic
- easily modified, shared, transferred
- 30 samples processed at one time
- Relatively inexpensive

## Objectives of Project

- Investigate effects of culture conditions on the production of fatty acids by selected species of *Phytophthora*
- Develop and standardize methods for generating fatty acid profiles for *Phytophthora* spp.
- Investigate variability in fatty acid profiles among these species

## Dendrogram Based 

**Dendrogram Based **
**on FAME Analysis**

## FAME Identification: Summary

- Amounts of each FA varied among species
- Factors affecting FA production determined
- Standard procedure for FAME analysis was developed
- FAME profiles appear to be effective for identification of species
- AFLP analysis supported FAME utility

## FAME Identification: Future & Value

- Future Research
- confirm utility with additional species
- construct FAME database with known isolates
- validate database with “unknown” isolates
- Value of Research to Stakeholders
- provide a rapid and inexpensive procedure for identification to diagnostic labs worldwide
- expedite studies on management of Phytophthora diseases

## Why Characterize Pathogen Populations ??

- Define morphological & physiological characters
- aid in identification
- sensitivity to mefenoxam & other fungicides
- Occurrence & distribution of mating types
- potential for genetic variation & adaptation
- Pathogenicity & virulence
- identify new hosts, expand known host range
- determine relative virulence
- Ultimately—better disease management

## Population of Phytophthora cinnamomi

- Predominant species attacking nursery crops
- 51 isolates primarily from woody plants in SC
- recovered between 1995 & 2000 by PP Clinic
- 49 isolates A2 & 2 isolates A1
- All isolates sensitive to mefenoxam
- EC50 values: 0.04-0.20 mg/L
- AFLP analyses
- isolates very similar  genetically
- implications for sources of inoculum...

## Population of Phytophthora nicotianae

- Predominant species attacking bedding plants, herbaceous perennials, *Buxus* spp.
- 108 isolates collected in SC during 1995-2000
- Both A1 & A2 mating types present
- A2 most common
- Some isolates resistant to mefenoxam
- EC50 values = 300-700 mg/L
- 29 potentially new hosts under investigation
- Virulence among isolates appears to differ

## Potential “New” Hosts for P. nicotianae

*Agapanthus*
*Aruncus*
*Ceratostigma plumbaginoides*
*Delosperma*
*Gaura*
*Hemerocallis*
*Hibiscus syriacus*
*Kniphofia*
*Lamium*

*Penstemon*
*Petunia*
*Phlox paniculata*
*Rodgersia*
*Salvia* x *superba*
*Sedum*
*Tiarella*
*Vinca minor*
*Viola* x *wittrockiana*

## New hosts for P. nicotianae

- Sedum—root rot

- Petunia—root rot

## Population of Phytophthora palmivora

- Previously not found on ornamental crops in the Southeast
- Primarily attacks *Hedera* spp. & *Fatsia japonica*
- both in the family Araliaceae
- 38 isolates collected in SC during 1995-2000
- Morphologically similar to *P. nicotianae*
- Only A1 mating type found
- All isolates very sensitive to mefenoxam
- EC50 values < 0.10 mg/L

## Pathogen Populations: Future & Value

- Future Research
- compare populations from ornamental crops to those from natural ecosystems
- determine virulence of isolates from different populations
- identify sources of primary inoculum
- Value to Stakeholders
- identify new host species
- pinpoint sources of inoculum
- more effective disease management strategies

## Phytophthora Culture Collection

- Maintain a collection of 1000+ isolates
- valuable resource
- distribute isolates to colleagues
- receive isolates from colleagues
- Constructing an ACCESS database so information is readily accessible
- in cooperation with Dept. of Computer Science
- will be posted on the web

## Questions??