سهیلا میرزایی

Grape is a major horticultural crop with a high nutritional value in the world. The optimal geographic and climatic conditions in Iran have positioned it as one of the most important regions for grape cultivation in the world. Black rot, caused by Aspergillus niger, is a highly destructive fungal disease that affects the grapes by targeting wounded areas. It causes crushing of the grapes, the falling of berries, and reduces transportation and storage properties (Ponsone et al., 2011). Various methods, such as fumigating bunches with sulfur dioxide and storing them in a modified atmosphere, have been used to control fungal rot and prolong the shelf life of grapes. However, each method has its limitations. Grape fumigation with sulfur gas is harmful to human health (Duarte-Sierra et al., 2016) and the efficiency of modified atmospheric storage on rot control and maintaining the quality of grapes depends on the type of variety, storage temperature, and especially gas concentration (Himelrick, 2003).Given the lack of efficiency in traditional methods, it is imperative to introduce modern techniques that can effectively disinfect microorganisms. These advanced methods offer several advantages, including the preservation of crop quality, an increase in crop shelf life, the promotion of good health, and substantial economic benefits. A technique of this type includes using non-thermal (cold) plasma (NTP) technology to eliminate food microorganisms (Bourke et al., 2018). The effect of cold plasma at atmospheric pressure on the reduction of bacterial populations in food products such as lettuce, tomato, strawberry, and cherry tomato has been reported (Bermúdez-Aguirre et al., 2013; Pasquali et al., 2016; Ziuzina et al., 2014). Research has shown that cold plasma can effectively inactivate Aspergillus in various orchard and agricultural products (Butscher et al., 2016; Ghorashi et al., 2020; Selcuk et al., 2008). The effect of cold plasma on the quality characteristics of the product during the post-harvest period has also been investigated. Blueberries treated with cold plasma for less than 15 minutes showed remarkable results after 10 days, the fruit exhibited reduced lipid peroxidation and darkening, with no impact on the total anthocyanin content, pH, or firmness of the product (Hu et al., 2021). In a study by Rana et al. (2020), it was found that subjecting strawberries to 15 minutes of cold plasma with packaging after 5 days of storage at 25°C had no significant impact on pH, TSS, and moisture content of the fruit.The review of the literature reveals the absence of research on fungal disease control and grape quality evaluation following the use of NTP. This study aims to investigate the efficiency of plasma treatment in reducing the infection with Aspergillus fungi, along with examining the physical, chemical, and mechanical properties of Fakhri grape.

This research was conducted as a completely randomized design in a factorial experiment at four plasma levels (0, 10, 20, and 40 s) and five storage periods (1, 2, 3, 4, and 5 weeks) with three replications at 4°C.  A plasma generator was first designed and manufactured in this study. A specifically designed and fabricated plasma application probe was also developed for grape berries. The individual grape berries were then sterilized with 1% sodium hypochlorite under a laminar hood for 2 minutes. Afterward, they were rinsed three times with sterile distilled water to remove any remaining disinfectant residue from their surfaces. Sterilized berries were immersed in Aspergillus spore suspension with 105 spores.ml-1 concentration. Finally, all samples were dried on paper filters and prepared for different plasma treatment durations (0, 10, 20, and 40 s). The treated samples were stored at 4°C, and the infection percentage and microbial load were measured on a weekly basis. To assess the preservation quality, chemical parameters such as pH, TSS, and TA, physical parameters (color change and weight loss), and mechanical properties were measured every week. Additionally, thermal imaging was performed weekly.

Plasma application during storage significantly reduced the infection percentage and microbial load in Aspergillus-inoculated samples. At the end of the storage period, the infection percentage and microbial load in the 40-second plasma treatment were 5% and 2.5 CFU g-1 respectively, while in the control group, the infection percentage was 100% and the microbial load was 4 CFU g-1. At the end of the storage period, the lowest pH level in the plasma was observed for 40 s plasma. This could be attributed to effective contamination control, as fungal contamination leads to alkalization of the environment. The highest amount of TSS was also observed in control and 40 s plasma. But in the 10 and 20 s plasma treatment, the process of changes was gradual and not significant. The higher TSS level of control and 40 s plasma can be due to the weight loss caused by the spread of contamination and moisture leakage caused by damage to the tissue. This decrease in moisture leads to an apparent increase in the TSS index. Research has shown that plasma primarily affects the surface characteristics of products, and when applied with the appropriate voltage and duration, it does not alter the internal chemical properties (Hu et al., 2021). Over time, weight loss increased in all treatments. This increasing trend during the storage period is higher in control and 40 s plasma compared to 10 and 20 s plasma. Therefore, the weight loss in the control can be due to the spread of contamination and aging of the product over time. However, the weight loss in the 40-second plasma treatment can be due to the destruction of the fruit tissue caused by longer duration of the plasma application.In the current research, by increasing the duration of plasma application to 40 s, a significant decrease in L*, a*, and b* indices and an overall change in the color of the product was observed. Research shows that in blueberries, inappropriate duration of plasma treatment causes the loss of wax on the fruit surface and leads to darkening of the product (Hu et al., 2021). The highest and lowest changes in temperature drop were observed in the control treatment (5°C) and 10 and 20 s plasma (3 and 3.5°C, respectively). According to research, an increase in fungal contamination leads to a decrease in humidity, increases weight loss, and subsequently a decrease in product temperature. A decline in mechanical characteristics was noted for the control and plasma treated samples during the storage period. The lowest value for indicators was observed in the 40 s plasma treatment. However, no significant difference was observed in samples treated with plasma for less than 20 seconds compared to the control group up to the middle of the storage period. According to a report by Misra et al. (2014), plasma application can reduce tissue softness. Therefore, optimizing its plasma duration and intensity is very important (Pan et al., 2021).

Our experiments aimed to investigate the effect of NTP treatment on controlling Aspergillus infections while preserving the quality properties of Fakhri grapes. The obtained results are important for two main reasons. Firstly, an innovative probe was designed for plasma applications, specifically tailored to the shape and size of individual grapes in order to thoroughly cover them with plasma. Secondly, application of plasma was carried out for the first time and yielded valuable results, indicating that this technique can control fungal infections and preserve the chemical, physical, and mechanical properties of grapes.

In this study, the antagonistic activities of eleven isolates belonging to 10 species of Trichoderma fungi including Trichoderma harzianum, T. atroviride (two isolates), T. viride, T. orientalis, T. citrinoviride, T. asperellum, T. spirale, T. crassum, T. pseudokoningi and T. ceramicum against rhizoctonia solani AG2-2, the causal agent of sugar beet root rot, were evaluated in a completely randomized design with four replications. Results showed that all Trichoderma isolates reduced the growth of pathogen significantly and the highest antagonistic effects were observed in dual culturing test in T. harzianum Z1 isolate, which caused 76.57% inhibition of pathogen mycelial growth. In greenhouse experiments, the efficacy of four selected Trichoderma isolates on sugar beet root rot control in Shirin cultivar was evaluated. Results showed that T. harzianum Z1, T. atroviride Z2, and T. orientalis Z4 caused 71.1, 66.6, and 58.3% decrease in root rot severity, respectively. In field experiments (2013-14) conducted in Hamedan Agricultural and Natural Resources Research Center, the effect of selected Trichoderma isolates in comparison with fungal treatment (carboxin-thiram) and control treatment on the occurrence and severity of root rot was evaluated through artificial contamination by Rhizoctonia solani. Results showed that selected Trichoderma isolates were significantly different in terms of disease control and T. harzianum Z1 isolate caused 66.4% reduction in the incidence of infection and 56% reduction in root rot severity compared with control. Therefore, this isolate is considered as the most effective antagonist in decreasing of Rhizoctonia root rot disease of sugar beet root.

Taxol is a diterpenoid compound that was first isolated from yew tree (Taxus brevifolia) and later from other plants such as Corylus avellana. Studies have shown that some of the endophytic fungi isolated from these plants are also capable of producing taxol. DBAT gene is one of the key genes in taxol biosynthesis pathway that catalyzes the synthesis of Baccatin III، one of the main precursors in taxol biosynthesis. The aim of this study was to investigate taxol production by endophytic fungi isolated from Corylus avellana.

In this case-control study، endophytic fungi were isolated from hazelnut trees in the Fandoghlo area، Ardabil province، and purified through hyphal tip method. Genomic DNA was extracted using CTAB method. The presence of DBAT gene was examined by polymerase chain reaction (PCR). Taxol production in fungal media was investigated via TLC (Thin Layer Chromatography) method.

After purification، 60 fungi were isolated from different organs of hazelnut trees and the presence of DBAT genes in 12 isolates was proved by PCR with specific primers. Investigation of taxol production in culture of these isolates showed that 7 isolates were capable of producing taxol in laboratory conditions.

A group of endophytic fungi isolated from hazelnut، grown in the North West of Iran، had DBAT gene، encoding a key enzyme in the taxol biosynthesis pathway، and some were able to produce taxol in vitro.

Progression of Fusarium head blight on six wheat cultivar Falat, Tajan, Zagross, Millan, Frontana, Sumai#3 and one resistant line ( SHA3/ SERI/NANJING 833//Lira) was evaluated by various epidemiological models including Monomolecular, Logistic, Gompertz, Log-Logistic and Weibull, under controlled conditions in the greenhouse. In Falat and Tajan cultivars, there was no difference between various models' coefficient of determination (R2), and efficiency for all of them were the same. For Zagross, Monomolecular model with highest R2 and lowest MSe (R2=0.9834, MSe=0.00011), and in Millan, Monomolecular (R2=0.9741, MSe=0.00035) and Weibull models (c=2) (R2=0.9744, MSe=0.00045) were considered to be the best fitted models. In Frontana, Weibull model (c=2) with highest R2 and lowest MSe (R2=0.9918, MSe= 0.000076) was preferred to the others. For resistant line also the Weibull model (c=2) (R2=0.9901, MSe= 0.000089) was accepted as the best fitted model. Sumai#3 cultivar showed little infection and naturally, none of these models were fitted to its data. The nature of monocyclic or polycyclic of the disease was also studied in the present investigation in Falat cultivar. The results showed that spores produced on inoculated spikes could not infect intact spikes.