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

Citation
S. Moricca et al., Antagonism of the two-needle pine stem rust fungi Cronartium flaccidum andPeridermium pini by Cladosporium tenuissimum in vitro and in planta, PHYTOPATHOL, 91(5), 2001, pp. 457-468
Citations number
59
Categorie Soggetti
Plant Sciences
Journal title
PHYTOPATHOLOGY
ISSN journal
0031949X → ACNP
Volume
91
Issue
5
Year of publication
2001
Pages
457 - 468
Database
ISI
SICI code
0031-949X(200105)91:5<457:AOTTPS>2.0.ZU;2-Q
Abstract
Selected isolates of Cladosporium tenuissimum were tested for their ability to inhibit in vitro aeciospore germination of the two-needle pine stem rus ts Cronartium flaccidum and Peridermium pini and to suppress disease develo pment in planta. The antagonistic fungus displayed a number of disease-supp ressive 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 electr on microscopy showed that rust spores were directly parasitized by Cladospo rium tenuissimum and that the antagonist had evolved several strategies to breach the spore wail and gain access to the underlying tissues. Penetratio n occurred with or without appressoria. The hyperparasite exerted a mechani cal force to destroy the spore structures (spinules, cell wall) by direct c ontact, penetrated the aeciospores and subsequently proliferated within the m. However, an enzymatic action could also be involved. This was shown by t he dissolution of the host tell wall that comes in contact with the myceliu m of the mycoparasite, by the lack of indentation in the host wall at the c ontact site, and by the minimal swelling at the infecting hyphal tip. Cultu re filtrates of the hyperparasite inhibited germination of rust propagules. A compound purified from the filtrates was characterized by chemical and s pectroscopic 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. Beca use the fungus is an aggressive mycoparasite, produces fungicidal metabolit es, and can survive and multiply in forest ecosystems without rusts, it see ms a promising agent for the biological control of pine stem rusts in Europ e.