Identification of antifungal compound isolated from Cercospora sp. ME202 and evaluation of the inhibitory activity against Colletotrichum orbiculare

Abstract

Abstract Cucumber anthracnose, an important disease caused by Colletotrichum orbiculare, is controlled using fungicides. However, this can lead to the development of fungicide resistance. We have previously shown that an ethyl acetate extract of the culture filtrate of Cercospora sp. ME202 (ME202-ECF) exhibits fungicidal activity and inhibits the formation of anthracnose lesions caused by C. orbiculare. However, studies on the control of plant diseases using the antimicrobial compounds produced by Cercospora have not been conducted. Here, we aimed to isolate and identify antifungal compounds produced by Cercospora sp. ME202 and evaluate their antifungal activity against C. orbiculare. We identified traversianal, a tricyclic diterpenoid aldehyde with a molecular weight of 316.4 from ME202-ECF. The traversianal structure was determined by liquid chromatography-mass spectrometry using electrospray ionization and nuclear magnetic resonance spectroscopy after purification by column chromatography and high-performance liquid chromatography. The inhibitory activity of isolated traversianal was detected as a mycelial growth inhibition zone at Rf 0.92 by thin layer chromatography bio-assay. Traversianal also inhibited the conidial germination of C. orbiculare at 2–10 ppm and exhibited fungicidal activity at 5–10 ppm. Furthermore, pretreatment of cucumber leaves with 10, 20, and 30 ppm traversianal significantly suppressed lesion formation in C. orbiculare without phytotoxicity. These results indicate that the traversianal produced from Cercospora sp. ME202 is a potential candidate as a new fungicide against C. orbiculare.