Leonardo José Silva,
Eduardo José Crevelin,
Wallace Rafael Souza,
Luiz Alberto Beraldo Moraes,
Itamar Soares Melo, and
Tiago Domingues Zucchi
First, third, fifth, and sixth authors: Laboratório de Microbiologia Ambiental, EMBRAPA, Jaguariúna, Brazil; and second and fourth authors: Laboratório de Espectrometria de Massa Aplicado à Química de Produtos Naturais, FFCLRP/USP, Ribeirão Preto, Brazil.
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Accepted for publication 7 June 2014.
A recently described actinomycete species (Streptomyces araujoniae ASBV-1T) is effective against many phytopathogenic fungi. In this study, we evaluated the capacity of this species to inhibit Botrytis cinerea development in strawberry pseudofruit, and we identified the chemical structures of its bioactive compounds. An ethyl acetate crude extract (0.1 mg ml−1) of ASBV-1T fermentation broth completely inhibited fungus growth in strawberry pseudofruit under storage conditions. The crude extract was fractionated by preparative high-performance liquid chromatography; the active fraction was further evaluated by tandem mass spectrometry. ASBV-1T produced a multiantibiotic complex with ionophoric properties. This complex contained members of the macrotetralides class (including monactin, dinactin, trinactin, and tetranactin) and the cyclodepsipeptide valinomycin, all of which were active against B. cinerea. Furthermore, the addition of 2 mM MgSO4 and 1 mM ZnSO4 enhanced macrotetralide and valinomycin production, respectively, in the culture broth. These compounds are considered to be the main active molecules that S. araujoniae produces to control B. cinerea. Their low to moderate toxicity to humans and the environment justifies the application of ASBV-1T in biological control programs that aim to mitigate the damage caused by this phytopathogen.
© 2014 The American Phytopathological Society