Inhibitory and stimulatory effects of essential oils and individual monoterpenoids on growth and sporulation of four soil-borne fungal isolates of Aspergillus terreus, Fusarium oxysporum, Penicillium expansum, and Verticillium dahliae

Abstract

The effect of essential oils and individual monoterpenoids on soil-borne fungi, in pure and mixed cultures, in growth media and in the soil environment, was investigated. Essential oils were extracted from lavender (Lavandula stoechas), oregano (Origanum vulgare subsp. hirtum), sage (Salvia fruticosa) and spearmint (Mentha spicata). The monoterpenoids tested were fenchone, carvacrol, 1,8-cineole, carvone, α-pinene and terpinen-4-ol.Their effect was examined on growth and sporulation of Aspergillus terreus, Fusarium oxysporum, Penicillium expansum and Verticillium dahliae isolated from an organic cultivation of tomato. All tested essential oils and individual monoterpenoids inhibited mycelial growth in all fungi and conidial production in most fungi. The strongest inhibitory activity on mycelial growth was exhibited by oregano and spearmint oils and by carvacrol and carvone, respectively their main constituents. The inhibitory activity was clearly fungistatic in A. terreus and F. oxysporum but fungicidal in V. dahliae. On sporulation, clearly stimulatory effects were observed alongside inhibitory ones. Conidial production was always promoted by α-pinene in P. expansum and by sage oil in F. oxysporum. At certain dosages it was promoted by cineole and carvone in F. oxysporum, and by lavender oil in A. terreus and V. dahliae. Experiments with carvone and carvacrol against mixed fungal cultures in a soil environment showed that V. dahliae was the most sensitive and A. terreus the most tolerant of the four fungi. Our results demonstrate strong but divergent effects and selectivity of action of the lower terpenoids on fungal strains that can become serious pests of tomato. Of special importance is the complete inhibition of growth and conidial production of V. dahliae, a pathogen otherwise very resistant to chemical control.

Susceptibility toVerticillium longisporumis linked to monoterpene production byTPS23/27 in Arabidopsis

“…The modified hydrocarbons are referred to as terpenoids or terpene‐like compounds, and are primarily found in a wide variety of higher plant families. Commonly, complex blends of terpenoids, referred to as essential oils, are emitted from plants and the individual compounds may exert both inhibiting and promoting effects on microorganisms (Lucini et al ., ; Droby et al ., ; Kadoglidou et al ., ). Here, we show that plants emitting higher amounts of TPS23/27‐produced monoterpenes are significantly more susceptible to V. longisporum .…”

Edible coating composed of chitosan andSalvia fruticosaMill. extract for the control of grey mould of table grapes

“…Salvia fruticosa Mill., commonly known as Greek sage, has received attention due to its health‐promoting properties and economic importance. Research so far has emphasised the antimicrobial activity of the EOs of the species, while the in vitro activity of its polar extracts was recently screened …”

Lignocellulolytic Capability of Endophytic Phyllosticta sp.

“…On lavender flower and lavender stem biomass agar, the agar at the margin of the leading edge of most fungal strains changed to a red color during 1-3 days of incubation and turn darker after 7-20 days, except for P. citrimaxima. Most of strains could produce pycnidia and conidia on biomass residue (Figure 3 growth [43]. This result suggests that in the residual biomass after oil extraction may contain compound(s) which are stimulatory to growth and thus opens the possibility of using lavender by-products for biomass treatment processes within a bio refinery concept.…”