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Infection and development of Phoma medicaginis on moderately rersistant and susceptible alfalfa genotypes

Permanent URL:
http://handle.nal.usda.gov/10113/16140
File:
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Abstract:
In North America, spring black stem and leaf spot, caused by Phoma medicaginis, is one of the most important diseases of alfalfa (Medicago sativa). Symptoms appear initially as small, dark brown to black spots that eventually enlarge and on leaves the spots are associated with chlorosis and defoliation. The infection process of P. medicaginis was previously investigated on susceptible alfalfa genotypes, but little is known about this process with alfalfa plants with differing degrees of resistance. We used light and scanning electron microscopy to follow infection and development of P. medicaginis from pycnidiospore deposition on leaf surfaces through pycnidia formation on selected susceptible and resistant alfalfa genotypes from the USDA core collection. In both old and young leaves, spore germination, penetration, development of mycelium, and pycnidia formation were delayed by approximately 24 h on moderately resistant alfalfa genotypes compared with susceptible genotypes. A similar delay in visible symptom development occurred until about 192 h after inoculation, after which the amount of chlorosis in all genotypes was similar.
Author(s):
Castell-Miller, C.V. , Zeyen, R.J. , Samac, D.A.
Subject(s):
Phoma medicaginis , plant pathogenic fungi , fungal spores , spore germination , pathogenicity , mycelium , disease resistance , Medicago sativa , alfalfa , genetic variation
Format:
p. 290-298.
Note:
Includes references
Source:
Canadian journal of plant pathology = Revue Canadienne de phytopathologie 2007 July-Sept., v. 29, no. 3
Language:
English
Year:
2007
Collection:
Journal Articles, USDA Authors, Peer-Reviewed
Rights:
Works produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted.