Antagonistic activity of fungi of Olea europaea L. against Colletotrichum acutatum

Abstract

Fungi naturally present in olive trees were identified and tested for their antagonistic potential against Colletotrichum acutatum. A total of 14 isolates were identified, 12 belonged to genera Alternaria, Epicoccum, Fusarium, Aspergillus, Anthrinium, Chaetomium, Diaporthe, Nigrospora, one to family Xylariaceae and one was unclassified. All fungal isolates showed some inhibitory action over the growth of C. acutatum during dual culture growth, however, when agar-diffusible tests were performed only five fungal isolates caused C. acutatum growth inhibition: Alternaria sp. isolate 2 (26.8%), the fungus from Xylariaceae family (14.3%), Alternaria sp. isolate 1 (10.7%); Diaporthe sp. (10.7%), Nigrospora oryzae (3.5%). Volatile substances produced by these isolates were identified through gas-chromatography techniques, as phenylethyl alcohol, 4-methylquinazoline, benzothiazole, benzyl alcohol, lilial, galaxolide, among others. These inhibitory volatiles could play a significant role in reduction of C. acutatum expansion in olive and their study as potential biocontrol agents should be further explored.

Fungal endophytic communities associated to the phyllosphere of grapevine cultivars under different types of management

“…Within Ascomycota, the Dothideomycetes were the most representative (71 % of total isolates) and within those, the Pleosporales (66 %), which have shown to be one of the main components of the endophytic mycota of many woody plants including grapevine (Gonzalez & Tello 2011;Pancher et al 2012). This is mainly due to Alternaria and Epicoccum species that are the most frequent among fungal endophytes in grapevine, as well as in other plants (Gonzalez & Tello 2011;Grisan et al 2011;Pancher et al 2012;Landum et al 2016) and have been studied as promising biocontrol agents. Alternaria species are usually the principal fungal component of endophytic communities in phyllospheres, mostly due to their particular life style, producing highly melanised hyphae capable to resist and grow under intense UV radiations.…”

Antifungal activity of native yeasts from different microenvironments against Colletotrichum gloeosporioides on ripe olive fruits

“…Most of the selection techniques of biocontrol agents are based on detection of antifungal diffusible metabolites (antibiosis) in dual culture, determining inhibition of vegetative fungal growth (Balouiri et al, 2016;Capdeville et al, 2007;Chanchaichaovivat et al, 2007;El-Tarabily and Sivasithamparam, 2006;Landum et al, 2016;Lima et al, 2012;Nally et al, 2012;Rosa-Magri et al, 2011). However, other researchers consider competition for nutrients and space the most important mode of action of antagonistic yeasts against fungal pathogens (Droby et al, 1989;Spadaro and Droby, 2016).…”

“…Yeasts that showed different in vitro inhibition strategies were assessed for their efficacy to reduce the incidence and severity of anthracnose in vivo. Although Landum et al (2016) conducted an in vitro screening of microorganisms against C. acutatum, causal agent of anthracnose in olive fruits, the authors only evaluated the production of volatile and nonvolatile compounds by phyllosphere filamentous fungi and they did not verify their antifungal activity in vivo. Hence, the present study is the first that reports on the antagonistic activity of indigenous yeasts against C. gloeosporioides assayed in wounded ripe olive fruits.…”

“…Colletotrichum genus includes a large number of fungal species that cause high yield losses in numerous crops (Landum et al, 2016;Olivieria et al, 2005).…”

“…There exists only one study that has reported biocontrol characteristics of yeastlike fungi belonging to Aureobasidium pullulans against C. acutatum in olive fruits (Segura Pérez, 2003). Landum et al (2016) showed that filamentous fungi isolated from olive leaves in vitro inhibited fungal growth of C. acutatum. To our knowledge, the contribution of yeasts to biocontrol C. gloeosporioides in olive fruits has not been examined yet.…”