Antagonism of the two-needle pine stem rust fungi Cronartium flaccidum and Peridermium pini by Cladosporium tenuissimum in vitro and in planta

Moricca, S, Ragazzi, A, Mitchelson, KR and Assante, G (2001) Antagonism of the two-needle pine stem rust fungi Cronartium flaccidum and Peridermium pini by Cladosporium tenuissimum in vitro and in planta. Phytopathology, 91 5: 457-468. doi:10.1094/PHYTO.2001.91.5.457


Author Moricca, S
Ragazzi, A
Mitchelson, KR
Assante, G
Title Antagonism of the two-needle pine stem rust fungi Cronartium flaccidum and Peridermium pini by Cladosporium tenuissimum in vitro and in planta
Journal name Phytopathology   Check publisher's open access policy
ISSN 0031-949X
Publication date 2001
Sub-type Article (original research)
DOI 10.1094/PHYTO.2001.91.5.457
Volume 91
Issue 5
Start page 457
End page 468
Total pages 12
Place of publication St Paul. Minn. USA
Publisher The American Phytopathological Society
Collection year 2001
Language eng
Subject C1
270403 Plant Pathology
780105 Biological sciences
Abstract Selected isolates of Cladosporium tenuissimum were tested for their ability to inhibit in vitro aeciospore germination of the two-needle pine stem rusts Cronartium flaccidum and Peridermium pini and to suppress disease development in planta. The antagonistic fungus displayed a number of disease-suppressive mechanisms. Aeciospore germination on water agar slides was reduced at 12, 18, and 24 h when a conidial suspension (1.5 x 10(7) conidia per ml) of the Cladosporium tenuissimum isolates was added. When the aeciospores were incubated in same-strength conidial suspensions for 1, 11, 21, and 31 days, viability was reduced at 20 and 4 degreesC. Light and scanning electron microscopy showed that rust spores were directly parasitized by Cladosporium tenuissimum and that the antagonist had evolved several strategies to breach the spore wail and gain access to the underlying tissues. Penetration occurred with or without appressoria. The hyperparasite exerted a mechanical force to destroy the spore structures (spinules, cell wall) by direct contact, penetrated the aeciospores and subsequently proliferated within them. However, an enzymatic action could also be involved. This was shown by the dissolution of the host tell wall that comes in contact with the mycelium of the mycoparasite, by the lack of indentation in the host wall at the contact site, and by the minimal swelling at the infecting hyphal tip. Culture filtrates of the hyperparasite inhibited germination of rust propagules. A compound purified from the filtrates was characterized by chemical and spectroscopic analysis as cladosporol, a known beta -1,3-glucan biosynthesis inhibitor. Conidia of Cladosporium tenuissimum reduced rust development on new infected pine seedlings over 2 years under greenhouse conditions. Because the fungus is an aggressive mycoparasite, produces fungicidal metabolites, and can survive and multiply in forest ecosystems without rusts, it seems a promising agent for the biological control of pine stem rusts in Europe.
Keyword Plant Sciences
Uredinicola
Adhesion
Q-Index Code C1

Document type: Journal Article
Sub-type: Article (original research)
Collection: School of Information Technology and Electrical Engineering Publications
 
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Created: Tue, 14 Aug 2007, 16:55:05 EST