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Title: Diversity and antifungal activity of the endophytic fungi associated with the native medicinal cactus Opuntia humifusa (Cactaceae) from the United States

Author
item HUGHES, ALICE F.S. - Universidade Federal De Minas Gerais
item Wedge, David
item Cantrell, Charles
item CARVALHO, CAMILA - Universidade Federal De Minas Gerais
item Pan, Zhiqiang - Peter
item MORAES, RITA - University Of Mississippi
item MADOXX, VICTOR - Mississippi State University
item ROSA, LUIZ - Universidade Federal De Minas Gerais

Submitted to: Microbiological Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/8/2015
Publication Date: 3/21/2015
Publication URL: http://handle.nal.usda.gov/10113/62255
Citation: Hughes, A., Wedge, D.E., Cantrell, C.L., Carvalho, C.R., Pan, Z., Moraes, R.M., Madoxx, V.L., Rosa, L.H. 2015. Diversity and antifungal activity of the endophytic fungi associated with the native medicinal cactus Opuntia humifusa (Cactaceae) from the United States. Microbiological Research. 175:67-77.

Interpretive Summary: Endophytic fungi are those living inside plant tissues or organs, without causing them any harmful symptoms, including giving greater host plant resistance to biotic and/or abiotic stresses. Different studies reported that plants colonized by endophytic fungi represent an important repository of the fungal diversity and new species. The endophytic fungal community associated with the native cactus Opuntia humifusa in the United States was investigated and its potential for providing antifungal compounds. A total of 108 endophytic fungal isolates were obtained and identified by molecular methods into 17 different taxa. The most frequent species associated with O. humifusa were Alternaria sp. 3, Aureobasidium pullulans and Diaporthe sp. Six extracts of endophytes showed antifungal properties. From the extract of B. mediterranea we isolated the compound 5-methylmellein that displayed moderate antifungal activity against the phytopathogenic fungi Phomopsis obscurans. Our results suggest that native medicinal cacti of the United States can live symbiotically with rich and diverse endophytic communities and may be a source of bioactive molecules, including those able to inhibit or control plant disease pathogens.

Technical Abstract: The endophytic fungal community associated with the native cactus Opuntia humifusa in the United States was investigated and its potential for providing antifungal compounds. A total of 108 endophytic fungal isolates were obtained and identified by molecular methods into 17 different taxa of the genera Alternaria, Aureobasidium, Biscogniauxia, Cladosporium, Cryptococcus, Curvularia, Diaporthe, Epicoccum, Paraconiothyrium, Pestalotiopsis and Phoma. The most frequent species associated with O. humifusa were Alternaria sp. 3, Aureobasidium pullulans and Diaporthe sp. The fungal community had a high richness and diversity; additionally, the accumulation curves of species-rich suggest that a full inventory of endophytic species is close to being completed. Six extracts of endophytes showed antifungal properties and 1H NMR analyses of the extracts of Alternaria sp. 5 Ohu 8B2, Alternaria sp. 3 Ohu 30A, Cladosporium funiculosum Ohu 17C1 and Paraconiothyrium sp. Ohu 17A indicated the presence of functional groups associated with unsaturated fatty-acid olefinic protons and fatty acid methylene and methyl protons. GC-FID analysis of these extracts confirmed the presence of a mixture of different fatty acids. The 1H NMR analyses of the extracts of Biscogniauxia mediterranea Ohu 19B showed the presence of aromatic compounds. From the extract of B. mediterranea we isolated the compound 5-methylmellein that displayed moderate antifungal activity against the phytopathogenic fungi Phomopsis obscurans. Our results suggest that native medicinal cacti of the United States can live symbiotically with rich and diverse endophytic communities and may be a source of bioactive molecules, including those able to inhibit or control plant disease pathogens.