VIEW ARTICLE

Light and Transmission Electron Microscopy of White Pine Blister Rust Canker. Bruce L. Welch, Biological Laboratory Technician, U.S. Department of Agriculture, Forest Service, Intermountain Forest and Range Experiment Station, Ogden, Utah 84401; Neil E. Martin, Forestry Sciences Laboratory, Logan, Utah, and Plant Pathologist, Intermountain Forest and Range Experiment Station, stationed at Forestry Sciences Laboratory, Moscow, Idaho. Phytopathology 65:681-685. Accepted for publication 20 January 1975. DOI: 10.1094/Phyto-65-681.

This report describes some reactions that occur between Pinus monticola bark cells and hyphal cells of Cronartium ribicola. A striking reaction is the affixation of hyphal cells to host cell walls. This is not a randomly occurring phenomenon, and it is an important host-pathogen relationship. Host cell walls beneath affixed hyphal cells stained lighter than the wall material on either side of this zone of affixation. Evidence is given for the possible presence of cellulase and pectinase activity in the zone of affixation. Described for the first time is an extracellular gel-like material that differs in electron density from the sheathing layer surrounding hyphal cells. In cross section, this material occurred on both sides of hyphal cells affixed to host cell walls. Strands of this gel-like material connected several hyphae that were near each other but not otherwise in contact. Also, this material was observed bridging spaces between host cell walls and unaffixed hyphal cells.