Abstract
The aim of the study was to determine the effectiveness of selected seven commercial essential oils (EsO) (grapefruit, lemongrass, tea tree (TTO), thyme, verbena, cajeput, and Litsea cubeba) on isolates of common Central European parasitic fungal species of Fusarium obtained from infected wheat kernels, and to evaluate the oils as potential natural fungicides. The study was conducted in 2 stages. At each stage, the fungicidal activity of EsO (with concentrations of 0.025; 0.05; 0.125; 0.25; 0.50; 1.0, and 2.0%) against Fusarium spp. was evaluated using the disc plate method and zones of growth inhibition were measured. At the first stage, the fungistatic activity of EsO was evaluated against four species of Fusarium from the Polish population (F. avenaceum FAPL, F. culmorum FCPL, F. graminearum FGPL and F. oxysporum FOPL). The correlation coefficient between the mycelial growth rate index (T) and the fungistatic activity (FA) was calculated. At the second stage, on the basis of the mycelium growth rate index, the effectiveness of the EsO in limiting the development of Fusarium isolates from the German population (F. culmorum FC1D, F. culmorum FC2D, F. graminearum FG1D, F. graminearum FG2D and F. poae FP0D) was assessed. The first and second stage results presented as a growth rate index were then used to indicate essential oils (as potential natural fungicides) effectively limiting the development of various common Central European parasitic species Fusarium spp. Finally, the sensitivity of four Fusarium isolates from the Polish population and five Fusarium isolates from the German population was compared. The data were compiled in STATISTICA 13.0 (StatSoft, Inc, CA, USA) at the significance level of 0.05. Fusarium isolates from the German population were generally more sensitive than those from the Polish population. The sensitivity of individual Fusarium species varied. Their vulnerability, regardless of the isolate origin, in order from the most to the least sensitive, is as follows: F. culmorum, F. graminearum, F. poae, F. avenaceum and F. oxysporum. The strongest fungicidal activity, similar to Funaben T, showed thyme oil (regardless of the concentration). Performance of citral oils (lemongrass and Litsea cubeba) was similar but at a concentration above 0.025%.
Highlights
The coefficients of fungistatic activity (FA) and mycelial growth rate index (T) were found to be highly correlated, which means that an increase in mycelial growth rate index causes a decrease in fungistatic activity
The T index was used to describe the relationship between the sensitivity of the isolates and the fungicidal activity of the essential oils (EsO)
EsO, which at low concentrations exhibit a broad spectrum of fungicidal activity against parasitic Fusarium spp. isolates, regardless of their origin
Summary
Species of Fusarium fungi are among the most diverse and widespread saprotrophs and pathogenic species in the environment Due to their ability to produce various metabolites, mainly mycotoxins, they pose a serious threat to humans and animals, and adversely affect soil fertility, biological productivity of agroecosystems, grassland, and forest ecosystems, and reduce the value of agricultural crops. The Fusarium ear blight caused by them is considered increasingly important in many parts of Europe, including Germany, Poland, France, Denmark, Italy, and Hungary. These toxigenic polyphagous pathogens occur in varying degrees on plants every growing season in all climate zones [4] as they spread and attack plants at all stages of development. In central Europe, the most dominant Fusarium ear blight-causing species are F. graminearum, F. poae, F. avenaceum, F. culmorum, F. langsethiae, and F. cerealis [5,6,7]
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