Skip to page content
USDA Forest Service
  
Treesearch

Research & Development Treesearch

 
Treesearch Home
About Treesearch
Contact Us
Research & Development
Forest Products Lab
International Institute of Tropical Forestry
Northern
Pacific Northwest
Pacific Southwest
Rocky Mountain
Southern Research Station
Help
 

Science.gov - We Participate


USA.gov  Government Made Easy


Global Forest Information Service

US Forest Service
P.O. Box 96090
Washington, D.C.
20090-6090

(202) 205-8333

You are here: Home / Search / Publication Information
Bookmark and Share

Publication Information

View PDF (126 KB bytes)

Title: Spatial and temporal aspects of tylosis formation in tanoak inoculated with Phytophthora ramorum

Author: Collins, Brad; Parke, Jennifer;

Date: 2008

Source: In: Frankel, Susan J.; Kliejunas, John T.; Palmieri, Katharine M., tech. coords. 2008. Proceedings of the sudden oak death third science symposium. Gen. Tech. Rep. PSW-GTR-214. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. p. 335

Publication Series: General Technical Report (GTR)

   Note: This article is part of a larger document. View the larger document

Description: Phytophthora ramorum is an oomycete pathogen that causes sudden oak death in several species of Fagaceae including tanoak (Lithocarpus densiflorus). Symptoms on tanoak include stem cankers and crown death. Stem infection was thought to be restricted to bark and cambium, but has recently been shown to include sapwood.

Woody tissue colonized by fungal pathogens often has a greater abundance of tyloses than non-infected tissue, and tyloses have been interpreted as a host defense response to infection. In this study, we are investigating the spatial and temporal development of tyloses in tanoak logs and living trees inoculated with P. ramorum.

In a preliminary study, 30 logs were freshly cut from disease-free tanoak trees in southern Oregon. Half the logs were inoculated at cambium depth with P. ramorum, and half were inoculated with a sterile agar plug (wounded controls). At 2, 4, and 7 weeks, sapwood tissue samples were fixed FAA and hand-sectioned for microscopy. Vessel diameters, the frequency of tylosis occurrence, the presence of hyphae, and the total vessel area occluded by tyloses were recorded. P. ramorum appeared to induce tylosis formation in tanoak sapwood by four weeks after inoculation. The spread of hyphae was more rapid than the formation of tyloses, indicating that tyloses may not be an effective defense response in limiting the growth of the pathogen. The relatively slow tylosis formation within tanoak sapwood in response to P. ramorum infection may provide insight as to why tanoak is so susceptible to this pathogen.

An unexpected finding was the reduction in the frequency of tylosis occurrence in inoculated logs from four to seven weeks. As the lesions developed, tylosis frequency increased in the xylem vessels. However, tyloses seem to become less frequent within the lesion near the point of inoculation and more frequent near the margin of the lesion. The reduction in tyloses may be due to hyphae within the lesion secreting enzymes that degrade the tylosis cell wall or elicitins that induce a hypersensitive response.

A field study is underway to examine spatial and temporal aspects of P. ramorum infection in relation to tylosis formation and specific conductivity of sapwood in living trees. Tanoak trees in California were inoculated with the pathogen in May 2006 and tissue samples were collected in September 2006. Additional samples will be collected in 2007 to track development of the infection and host response.

Keywords: Sudden oak death, xylem, host response, stem canker

Publication Notes:

  • We recommend that you also print this page and attach it to the printout of the article, to retain the full citation information.
  • This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.

XML: View XML

Citation:


Collins, Brad; Parke, Jennifer 2008. Spatial and temporal aspects of tylosis formation in tanoak inoculated with Phytophthora ramorum. In: Frankel, Susan J.; Kliejunas, John T.; Palmieri, Katharine M., tech. coords. 2008. Proceedings of the sudden oak death third science symposium. Gen. Tech. Rep. PSW-GTR-214. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. p. 335

 


 [ Get Acrobat ]  Get the latest version of the Adobe Acrobat reader or Acrobat Reader for Windows with Search and Accessibility

USDA logo which links to the department's national site. Forest Service logo which links to the agency's national site.