Busqueda de endófitos aislados de la familia Burseraceae con actividad antifúngica
Screening for antifungal activity of endophytes isolated from Burseraceae
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Abstract
El control de fitopatógenos es normalmente basado en fungicidas sintéticos que pueden acarrear consecuencias desfavorables en los ecosistemas circundantes y generar resistencia en las poblaciones de microorganismos. La búsqueda de alternativas al control con fungicidas sintéticos a identificado a los endófitos como posibles biocontroladores de fitopatógenos y como una potencial fuente de metabolitos antifúngicos. En el presente estudio se aislaron endofitos fúngicos y bacterianos de tres especies de la familia Burseraceae y se enfrentaron con F. oxysporum y B. cinerea en condiciones in vitro. Extractos los endófitos con mayor actividad antifúngica fueron caracterizados por RP-HPLC-DAD-ESI-MS y algunos compuestos con posible actividad antifúngica fueron tentativamente identificados por sus valores de masas
Control of fungal pathogens is mainly addressed by chemically synthesized fungicides which, after a prolonged use, produce environment pollution and develop resistance. In this context, endophytes have been recognized as potential biocontrolers and also potential source of antifungal metabolites. Therefore, as part of our research on phytopathogen controllers, 355 fungal endophytes were isolated from Protium heptaphyllum and Trattinnickia rhoifolia (Burseraceae), both important etnobotanical tree species that produce secondary metabolites of agronomic and industrial interest. Endophytes were tested by in vitro dual culture against Fusarium oxysporum, an important phytopathogen of agronomic importance. Five endophytes exerted at least 40 % of inhibition on F. oxysporum growth. Ethyl acetate (EtOAc) extracts were obtained from the most-antagonistic fungi growth in three different liquid media. The extracts were tested against a conidial suspension of F. oxysporum by direct bioautography. Two extracts derived from fungi identified as Chaetomium globosum, F211_UMNG and Meyerozima sp. F281_UMNG exhibited inhibition of the pathogen growth. The isolate Chaetomium globosum, F211_UMNG was selected for a chemical profiling by RP-HPLC-DAD-ESI-MS and antifungal molecules such as cladosporin, chaetoatrosin A and chaetoviridin A were tentatively identified by their MS data. ------------------------------------------------------------
Phytopathogenic fungi Botrytis cinerea and Fusarium oxysporum are mayor threats in several crops. These pathogens are predominantly controlled by chemically synthesized fungicides whose constant use could result in environment detriment, and increased genetic resistance to these molecules, preventing an effective control of these organisms in field. Then, alternative methods for controlling pathogenic fungi rare being sought, resulting endophytes as a viable alternative to chemically synthesized fungicides due their interactions with others microorganisms and the reported roles in plant defense. In this work bacterial endophytes were isolated form Bursera simaruba, a tree that has been related to endophytes of remarkable potential in agriculture as Muscodor yucatensis. Five endophytes were isolated from leaves: four were identified as Bacillus sp. and one as Pseudomonas geniculata. Effects of these endophytes on B. cinerea and F. oxysporum were tested in vitro by using dual culture technique. Isolate B3_UMNG, identified as Bacillus sp., was the most effective isolate for inhibiting the colonial growth of both pathogens (61% for F. oxysporum and 79% for B. cinerea). The ethyl acetate extract from a B3_UMNG culture was therefore characterize by LC-MS. Multivariate analysis of the results along with literature comparison led to the tentative identification of lichenysin, a surfactin produced by Bacillus, as the main compound responsible of the antifungal activity.
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