Abstract

Competition has been reported as one of the mechanisms of the antagonistic action of Trichoderma harzianum against F. oxysporum. Competition between microorganisms occurs when a vital factor, such as nutrients or space, is available in limited quantity. Under these limiting conditions, production of inhibitory compounds able to stop or slow down the growth of other microorganisms confers on the producing microbe an ecological advantage over the competitor(s). The competitive capability of the T. harzianum isolate ITEM 908 (Th908) vs. F. oxysporum f. sp. lycopersici was improved via enhancement of the tolerance to growth-inhibitory metabolites produced by F. oxysporum. HPTLC and HPLC analyses led to the identification of fusaric acid (FA) as the major metabolite in culture filtrate of the phytopathogenic F. oxysporum strain ITEM 2797 (Fo2797). FA, a phytotoxin which has also been reported to be released in soil, was strongly inhibitory to T. harzianum as well to isolates of other Trichoderma species. Through UV-C irradiation and subsequent selection of mutants able to grow on PDA supplemented with culture extracts of Fo2797 or FA, two stable FA-tolerant mutants were isolated. The biocontrol capability of one selected UV-mutant with unaltered physiological features and rhizosphere competence was compared to that of the wild strain Th908 on tomato plants grown in a substrate heavily infested with Fo2797 in two separate trials. The reduction of the disease by the mutant strain was significantly (P < 0.01) higher than that achieved with the wild strain Th908. Based on the above results, the combined use of certain biocontrol strains of F. oxysporum and T. harzianum might be problematic, because of the production of FA by the biocontrol strains of F. oxysporum. Therefore, we investigated the compatibility of the FA-tolerant mutant strain of T. harzianum with biocontrol strains of F. oxysporum in microcosms wherein the two biocontrol agents were co-inoculated. Since UV-mutants are not regarded as GMO, their circulation and use is not subjected to restrictions and the improved strain could get the registration for field use in some countries more easily than strains derived by genetic transformation.

Autore Pugliese

• Altomare Claudio

Tutti gli autori

• Marzano M.; Branà M. T.; Altomare C.

Titolo volume/Rivista

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Anno di pubblicazione

2014

ISSN

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ISBN

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Numero di citazioni Wos

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Settori ERC

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Codici ASJC

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