Antifungal Activities of Volatile Secondary Metabolites of Four Diaporthe Strains Isolated from Catharanthus roseus

Abstract

Four endophytic fungi were isolated from the medicinal plant, Catharanthus roseus, and were identified as Diaporthe spp. with partial translation elongation factor 1-alpha (TEF1), beta-tubulin (TUB), histone H3 (HIS), calmodulin (CAL) genes, and rDNA internal transcribed spacer (ITS) region (TEF1-TUB-HIS--CAL-ITS) multigene phylogeny suggested for species delimitation in the Diaporthe genus. Each fungus produces a unique mixture of volatile organic compounds (VOCs) with an abundant mixture of terpenoids analyzed by headspace solid-phase microextraction (SPME) fiber-GC/MS. These tentatively-detected terpenes included α-muurolene, β-phellandrene, γ-terpinene, and α-thujene, as well as other minor terpenoids, including caryophyllene, patchoulene, cedrene, 2-carene, and thujone. The volatile metabolites of each isolate showed antifungal properties against a wide range of plant pathogenic test fungi and oomycetes, including Alternaria alternata, Botrytis cinerea, Colletotrichum gloeosporioides, Fusarium graminearum, and Phytophthora cinnamomi. The growth inhibition of the pathogens varied between 10% and 60% within 72 h of exposure. To our knowledge, the endophytic Diaporthe-like strains are first reported from Catharanthus roseus. VOCs produced by each strain of the endophytic Diaporthe fungi were unique components with dominant monoterpenes comparing to known Diaporthe fungal VOCs. A discussion is presented on the inhibitive bioactivities of secondary metabolites among endophytic Diaporthe fungi and this medicinal plant.

An Endophytic Diaporthe apiculatum Produces Monoterpenes with Inhibitory Activity against Phytopathogenic Fungi

“…This investigation showed that VOCs produced by the endophytic D apiculatum FPYF 3052 were able to inhibit the growth of fungal pathogens (Table 2). This result was consistent with evidence on the VOCs of some endophytic fungi of Diaporthe previously reported [7,14,15,17]. These fungi were recorded as Diaporthe sp.…”

“…The roots and leaf extracts of L. leucocephala have also demonstrated antimicrobial and antifungal activities [5]. At present, there is some evidence to show that endophytes could have a potential function in inhibiting harmful pests, like Aspergillus fumigatus, Botrytis cinerea, and Mycobacterium tuberculosis [6][7][8]. However, more endophytes of L. leucocephala need to be isolated and studied for their diversity and function in disease protection since only the ones studied so far are linked to nitrogen fixation, mycorrhizal associations, along with some seed-associated fungi [9,10].…”

“…In addition, volatile organic compounds (VOCs) of endophytic fungi are being prospected to become a unique venue of non-toxic or less harmful applications for the biocontrol of pests. The VOCs are also being examined as to their roles in the defense and inhibitive effects against pathogens and insects in plants [6,7]. Those endophytic strains of Diaporthe genus isolated from some plants or trees, such as Picrorhiza kurro [14], Odontoglossum sp.…”

“…Those endophytic strains of Diaporthe genus isolated from some plants or trees, such as Picrorhiza kurro [14], Odontoglossum sp. [15], and Catharanthus roseus [7,16], are able to produce a unique mixture of inhibitive bioactive VOCs against many important fungal pathogens associated with crops and trees. The alcohols and terpenes are dominant components of VOCs in some fungal strains from the genus [15,17].…”

“…Especially terpenoids are reported as major components in Diaporthe spp. [7,17]. Some terpenoids produced by Diaporthe spp.…”