Abstract

Competition is one of the potential mechanisms of the antagonistic action of Trichoderma harzianumagainst Fusarium oxysporum. The competitive capability of the T. harzianum isolate ITEM 908 (Th908)vs. an isolate of F. oxysporum f. sp. lycopersici was improved via enhancement of the tolerance togrowth-inhibitory metabolites produced by F. oxysporum. HPTLC and HPLC analyses led to the identificationof fusaric acid (FA) as the major metabolite in culture filtrate of the phytopathogenic F. oxysporumstrain ITEM 2797 (Fo2797). FA, a phytotoxin which has also been reported to be released in soil, totallyinhibited the growth of Th908 on PDA containing 120 lg of FA per gram in 3-day trials. Through UV-Cirradiation and subsequent selection of mutants able to grow on PDA supplemented with culture extractsof Fo2797 or FA, one stable tolerant mutant (Th908-5) with unaltered physiological features and rhizospherecompetence was isolated. The biocontrol capability of the UV-mutant Th908-5 was compared tothat of the wild-type strain Th908 on tomato plants grown in a substrate heavily infested with Fo2797 intwo separate trials. The reduction of the disease by Th908-5 was highly (P < 0.01) to extremely (P < 0.001)significant, while only marginally significant (P < 0.05) and inconsistent biocontrol was achieved byTh908. In addition, in non-inoculated vermiculite, Th908-5 increased the emergence and growth oftomato plants compared to the control. Th908 and Th908-5 were investigated for the expression of fivegenes (MDR ProB, MDR BrefA, MDR Protein2, Hydro II, ThPTR2) encoding proteins putatively associatedwith T. harzianum biocontrol function and involved in the mechanisms of multidrug resistance (MDR)or competition for space and nutrients. When the mutant strain was exposed to FA, the expression ofthe gene MDR ProB, encoding a protein associated with MDR was suppressed, suggesting a role for thegene in response to FA. Since UV-mutants are not regarded as genetically modified organisms (GMO)and their circulation and use is not subjected to restrictions that apply to strains derived by genetic transformation,the improved strain Th908-5 could be readily available for application in the field.

Autore Pugliese

• Altomare Claudio , Gallo Antonia

Tutti gli autori

• Marzano M.; Gallo A.; Altomare C.

Titolo volume/Rivista

Biological control

Anno di pubblicazione

2013

ISSN

1090-2112

ISBN

Non Disponibile

Numero di citazioni Wos

Nessuna citazione

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Numero di citazioni Scopus

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Settori ERC

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Codici ASJC

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