VIEW ARTICLE

Cytology and Histology

Ultrastructure of Heterodera glycines Parasitized by Arkansas Fungus 18. D. G. Kim, Research associate (former graduate assistant) Department of Plant Pathology, University of Arkansas, Fayetteville, AR 72701; R. D. Riggs, and K. S. Kim. Professors, Department of Plant Pathology, University of Arkansas, Fayetteville, AR 72701. Phytopathology 82:429-433. Accepted for publication 10 October 1991. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/Phyto-82-429.

Ultrastructure of Heterodera glycines cysts, eggs, and juveniles parasitized by Arkansas fungus 18 (ARF18) was studied with transmission and scanning electron microscopy. Transmission electron microscopy revealed that parasitized cysts, eggs, and first-stage juveniles in eggs were filled with ARF18 fungal hyphae. Numerous pores, apparently caused by fungal penetration, were found below the sclerotiumlike structures on the cyst cuticles. The cyst cuticles at the site of the sclerotiumlike structures appeared to have been dissolved. These results suggest that ARF18 penetrates the cyst cuticle enzymatically. The surface of diseased eggs was heavily furrowed. Hyphae of ARF18 have electron-transparent septa that contain simple pores associated with Woronin bodies. These characteristics suggest that ARF18 is an ascomycete fungus. This is the first descriptive report of direct penetration of a nematode cyst wall by a fungal biological control agent.