VIEW ARTICLE

Infection of Ectomycorrhizal and Nonmycorrhizal Roots of Shortleaf Pine by Nematodes and Phytophthora cinnamomi. Richard O. Barham, Formerly Graduate Assistant, Department of Plant Pathology and Plant Genetics, University of Georgia, Athens 30602, Present address: Forester, Weyerhaeuser Company, Philadelphia, Mississippi 39350; Donald H. Marx(2), and John L. Ruehle(3). (2)(3)Principal Plant Pathologists, U.S. Department of Agriculture, Forest Service, Southeastern Forest Experiment Station, Forestry Sciences Laboratory, Athens, Georgia 30602. Phytopathology 64:1260-1264. Accepted for publication 6 May 1974. DOI: 10.1094/Phyto-64-1260.

Ectomycorrhizae aseptically synthesized by Pisolithus tinctorius and Thelephora terrestris and nonmycorrhizal feeder roots on intact seedlings of Pinus echinata were placed in individual glass cylinders and inoculated with Tylenchorhynchus claytoni or Helicotylenchus dihystera and zoospores of Phytophthora cinnamomi. After 8 days of incubation, both T. claytoni and H. dihystera penetrated and migrated through the fungus mantle and Hartig net of ectomycorrhizae formed by each symbiont. Vascular tissues of ectomycorrhizae formed by both fungal symbionts were invaded by T. claytoni. H. dihystera disrupted the structural integrity of the fungus mantles of ectomycorrhizae, thereby creating infection courts for P. cinnamomi. Intracellular hyphae and vesicles of P. cinnamomi were found in cortex cells surrounded by the Hartig net of ectomycorrhizae parasitized by H. dihystera, P. cinnamomi did not infect ectomycorrhizae penetrated by T. claytoni. Results indicate that nematodes are able to modify resistance afforded pine hosts by fungus symbionts against P. cinnamomi attack.