Antifungal activity of the lemongrass and clove oil encapsulated in mesoporous silica nanoparticles against wheat's take-all disease.

Combined application of plant essential oils (EOs) with known antimicrobial effects and silica nanocapsules with high loading capacity and protection capability of the EOs make them proper candidates for creating environmentally friendly fungicides. In this study, EOs of the Lemongrass (LGO) and Clove (CO) were used against Gaeumannomyces graminis var. tritici (Ggt), a causal agent of take-all disease of wheat. To provide controlled delivery of the EOs, they were encapsulated into mesoporous silica nanoparticles (MSNPs) and then compared to the effects of pure EOs both in- vitro and in- vivo. MSNPs were synthesized via the sol-gel process. Various techniques such as Fourier transform infrared spectroscopy (FTIR), the Brunauer-Emmett-Teller (BET), thermogravimetric analysis (TGA), and UV-Vis spectroscopy were used to evaluate the successful loading of the EOs into the pore of MSNPs. The encapsulation efficiency (EE) was calculated as high as 84.24% for LGO and 80.69% for CO, while loading efficiency (LE) was determined 36% and 29% for LGO and CO, respectively. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) displayed spherical shapes and porous structures with average diameters of 50-70 nm. Recognition of the main components of the EOs via gas chromatographic-mass spectrometry (GC-MS) before and after the EO loading, detected eugenol and citral as the most frequent compounds in LGO and CO, respectively. For antifungal test in- vitro, selected concentrations of the pure EOs, EOs loaded in MSNPs (EOs- MSNPs) and Mancozeb ® fungicide based on pre-tests were mixed using potato dextrose agar (PDA). The inhibition percentage (IP) of fungal growth at each concentration, as well as minimum inhibition concentration (MIC) and minimum fungicidal concentrations (MFC) were obtained. The results indicated that antifungal effects in the encapsulated form increased by up to three times. In- vivo, the sterile wheat seeds were treated with pure EOs, EOs-MSNPs, and mancozeb at MFC concentration. Also, in order to keep on the EOs-MSNPs around the seeds, sodium alginate was used. The consequences of in- vivo experiments indicated that rate of disease control in presence of EOs-MSNPs and mancozeb was the same (~70%) and higher than pure EOs (LGO: 57.44%, CO: 49%). Also, improving the growth parameters in wheat plant, the covering of the EOs-MSNPs in alginate, had better control (84%) than that of EOs-MSNPs alone. Further, the release kinetics studies showed a gradual release of LGO and CO from MSNPs for four weeks in water and for five weeks in the soil-plant system. To the best of our knowledge, this is the first report of the control effect of LGO, CO, and their nanocapsule in MSNPs against the take-all disease of wheat. These results showed that the EOs-MSNPs can be a safe product for the efficient control of take-all disease in wheat crop.

Management of Strawberry Anthracnose Using Plant Essential Oils as Bio-fungicides, and Evaluation of Their Effects on Quality of Strawberry Fruit.

Colletotrichum nymphaeae is the causal agent of strawberry anthracnose, which is one of the most important disease affecting strawberry plant in Iran. This research aimed to apply the selected plant essential oils (EOs) such as Achillea millefolium, Mentha longifolia, and Ferula kuma to the management of strawberry anthracnose disease under in vitro, in vivo, and greenhouse conditions. In vitro tests indicated that all the EOs and fungicide were able to inhibit mycelial growth and conidial germination of the pathogen. Scanning electron microscopy (SEM) revealed that EOs significantly suppressed the mycelia growth and caused a change in morphology of fungal mycelia. The severity of strawberry anthracnose disease was significantly (p ≤ 0.05) reduced by all EOs under in vivo and greenhouse conditions. Results of all experiments showed that M. longifolia EO was the best EO to control C. nymphaeae. Also, EOs almost reduced weight loss and preserved firmness, ascorbic acid, total phenol, antioxidant activity (DPPH), and enzyme peroxidase activity in treated fruit. Moreover, EOs preserved the sensory quality of strawberry fruit during the storage period so that there were no significant differences between treatments (EOs) in their appearance, flavor, odor attributes, and overall evaluation compared to the control. Our results indicate that EOs are excellent bio-fungicides for the management of strawberry anthracnose.

Bioconversion of isoeugenol to vanillin and vanillic acid using the resting cells of Trichosporon asahii.

40 isoeugenol-tolerant yeasts were isolated from the rhizosphere soil samples which in turn were collected from aromatic plants in different regions of Iran, and further tested for their ability to grow on a minimal medium containing isoeugenol as the sole carbon and energy source. Nine isolates which were able to grow on isoeugenol were examined for their ability to convert isoeugenol into vanillin under growing cell experiments. Of the tested yeasts, the highest conversion efficiency was observed in isolate MP24. The isolate was identified as Trichosporon asahii based on morphological, biochemical and molecular (ITS region) characters and tested to effectively convert isoeugenol into vanillin under resting cell system. A comparative analysis of thin layer chromatography (TLC), UV-Vis spectrometry, and high-performance liquid chromatography (HPLC) verified that vanillin and vanillic acid are accumulated as two major metabolites using T. asahii strain MP24 resting cells. In the presence of 7.5 g/l of wet weight cells of the strain MP24 pre-grown on isoeugenol and harvested at the end of the exponential growth phase, the optimal concentration of vanillin reached 2.4 g/l with a molar conversion of 52.5% in the potassium phosphate buffer (100 mM, pH 5.8) supplemented with 5 g/l of isoeugenol and 2% (v/v) N,N-dimethylformamide (DMF). The total concentration of vanillin and vanillic acid obtained from the bioconversion process was 4.2 g/l (total molar yield of 88.3%). Until now, no data has been published on the conversion of isoeugenol into vanillin by the strains of the genus Trichosporon.