Abstract
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 degrees C. 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 wall 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 cell 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.
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Claims 9
Claim · model-written summary
Cladosporium suspensions reduced rust aeciospore germination on agar at 12, 18, and 24 hours.
- Taxon
- Two-Needle Pinet0
- Treatment
- conidial suspension (1.5 x 10(7) conidia per ml) of the Cladosporium tenuissimum isolatese0
- Interactor
- Cladosporium tenuissimumCladosporium tenuissimume0biocontrol_agent
- Outcome
- Aeciospore germinatione0
- Direction
- reducede0
- Value
- 12, 18, and 24 he0
Not reportedComparator
Verbatim
t0“Two-Needle Pine”
e0“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.”
Claim · model-written summary
Conidial suspensions reduced aeciospore viability after incubation at 20 and 4 degrees C.
- Taxon
- Two-Needle Pinet0
- Treatment
- same-strength conidial suspensionse0
- Outcome
- viabilitye0
- Direction
- reducede0
- Qualifier
- 20 and 4 degrees Ce0
Not reportedComparator
Verbatim
t0“Two-Needle Pine”
e0“When the aeciospores were incubated in same-strength conidial suspensions for 1, 11, 21, and 31 days, viability was reduced at 20 and 4 degrees C.”
Claim · model-written summary
Microscopy showed direct parasitism of rust spores by Cladosporium tenuissimum.
- Taxon
- Two-Needle Pinet0
- Interactor
- rust sporese0pathogen
- Second interactor
- Cladosporium tenuissimumCladosporium tenuissimume0biocontrol_agent
- Outcome
- rust spores were directly parasitizede0
Verbatim
t0“Two-Needle Pine”
e0“rust spores were directly parasitized by Cladosporium tenuissimum”
Claim · model-written summary
Cladosporium penetrated aeciospores with or without appressoria and proliferated within them.
Verbatim
t0“Two-Needle Pine”
e0“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.”
Claim · model-written summary
Cell wall dissolution suggested possible enzymatic activity in mycoparasitism.
Verbatim
t0“Two-Needle Pine”
e0“an enzymatic action could also be involved. This was shown by the dissolution of the host cell wall that comes in contact with the mycelium of the mycoparasite”
Claim · model-written summary
Culture filtrates inhibited rust propagule germination.
- Taxon
- Two-Needle Pinet0
- Treatment
- Culture filtrates of the hyperparasitee0
- Outcome
- germination of rust propagulese0
- Direction
- inhibitede0
Not reportedComparator
Verbatim
t0“Two-Needle Pine”
e0“Culture filtrates of the hyperparasite inhibited germination of rust propagules.”
Claim · model-written summary
A purified filtrate compound was identified as cladosporol.
Verbatim
t0“Two-Needle Pine”
e0“A compound purified from the filtrates was characterized by chemical and spectroscopic analysis as cladosporol, a known beta-1,3-glucan biosynthesis inhibitor.”
Claim · model-written summary
Cladosporium conidia reduced rust development on infected pine seedlings over two years.
- Treatment
- Conidia of Cladosporium tenuissimume0
- Interactor
- ruste0pathogen
- Second interactor
- Cladosporium tenuissimumCladosporium tenuissimume0biocontrol_agent
- Outcome
- rust developmente0
- Direction
- reducede0
- Qualifier
- over 2 yearse0
- Setting
- greenhouse conditionse0
PinusNot reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Conidia of Cladosporium tenuissimum reduced rust development on new infected pine seedlings over 2 years under greenhouse conditions.”
Claim · model-written summary
The authors consider Cladosporium a promising biological control agent for pine stem rusts in Europe.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“it seems a promising agent for the biological control of pine stem rusts in Europe.”