Enzymatic activity of the mycelium compared with oospore development during infection of pea roots by Aphanomyces euteiches

• Published in: Phytopathology Vol. 88; no. 9; pp. 992 - 996
• Main Authors: KJØLLER, R, ROSENDAHL, S
• Format: Journal Article
• Language: English
• Published: St. Paul, MN American Phytopathological Society 01-09-1998
• Subjects: Biological and medical sciences; Fundamental and applied biological sciences. Psychology; Fungal plant pathogens; Microbiology; Mycology; Pathogenicity, host-agent relations, miscellaneous strains, epidemiology; Pathology, epidemiology, host-fungus relationships. Damages, economic importance; Phytopathology. Animal pests. Plant and forest protection; Aphanomyces euteiches; Disease development; Plant pathogen; Mycosis; Root; Phycomycetes; Spores; Fungi; Infection; Pathogenicity; Grain legume; Life cycle; Symptomatology; Leguminosae; Enzymatic activity; Investigation method; Dicotyledones; Pisum sativum; Angiospermae; Spermatophyta; Mycelium; Thallophyta
• ISSN: 0031-949X; 1943-7684
• DOI: 10.1094/phyto.1998.88.9.992

ABSTRACT To describe the disease cycle of the root pathogen Aphanomyces euteiches, enzymatic activity in the mycelium was compared with the development of oospores in pea roots. Plants were inoculated with two zoospore concentrations to achieve different disease levels. Hyphae were stained for fungal alkaline phosphatase activity in the roots. Additionally, enzyme activity was measured after electrophoresis of an A. euteiches-specific glucose-6-phosphate isozyme. Development of oospores in the roots was measured after staining the oospores with trypan blue. In plants inoculated with the higher zoospore concentration, the enzymatic activity of the pathogen mycelium peaked 10 to 14 days after inoculation, when oospore formation was initiated. Oospore formation was associated with a gradual increase in disease symptoms. At the last harvest, plants inoculated with the higher zoospore concentration had died. In these plants, oospores were found in 90% of the root length, while the enzymatic activity of the mycelium was low. This suggests that the pathogen mycelium is only active on living plants and does not grow saprophytically on dead plant material.