مهار زیستی

Nowadays, medicinal plants have been expanded in the biological control of many plant pathogens. It is also widely recognized that tomato is an essential product in the food industry worldwide. The root-knot nematode (Meloidogyne spp.), a hazardous parasite in tomato plants, produces gall by feeding and reproducing in the root and consequently causes biochemical and physiological changes. It also provides a suitable environment for the activity of saprophytic fungi and other soil parasites, which indirectly results in serious damage to the plant. Therefore, this study aimed to examine the effect of fenugreek, lavender, borage and purslane plant extracts on controlling the root-knot nematode. Separate experiments in laboratory and greenhouse conditions were conducted as a factorial experiment in the form of a completely randomized design to investigate the effect of natural compounds of fenugreek, lavender, borage and purslane on the control of root-knot nematode in tomato. Nematode-infected tomato roots were collected, and after that, a single suitable egg mass was taken and placed near the tomato Falat cultivar root system; using the single egg mass method for nematode purification, nematode was identified and then propagated at the same tomato seedlings. After 70 days, the infected roots were cut into two-centimetre pieces and exposed to 10% sodium hypochlorite solution. After that, it was passed through a 400-mesh sieve. Eventually, the obtained egg suspension was used in the laboratory and greenhouse trials. First, water, ethanol, and acetone extracts were prepared from the mentioned plants to experiment. The laboratory section assessed the effect of extracts on larval mortality and the number of egg hatching after 24, 48, and 72 hours of exposure to 0, 250, 500, 750, and 1000 ppm extracts. Afterwards, these compounds' anti-nematode activity was investigated at the greenhouse condition by adding 0, 250, 500, 750, and 1000 ppm of the water extract to the pots containing tomato seedlings and nematode-infected soil. Finally, the obtained average data were compared based on the LSD test. The results revealed that water, ethanol, and acetone extracts of fenugreek, lavender, borage, and purslane had the highest inhibition properties in hatching nematode eggs, respectively. The highest inhibition rate was dedicated to 1000 ppm of the extract. Also, the greatest inhibition of egg hatching was observed in fenugreek water extract and 1000 ppm of the extracts, respectively. The highest number of unhatched eggs was perceived in 1000 ppm of fenugreek extract and 72 h after starting the experiment. According to the results, water extract was the most effective in destroying nematode larvae, followed by ethanol and acetone extracts. Fenugreek, lavender, borage, and purslane had the highest impacts on the mortality of second-instar larvae, respectively. Also, among different extracts, the concentration of 1000 ppm had the greatest effect compared to the control. The fenugreek extract application caused gall formation at the lowest level in the experiment. After fenugreek, the lavender, borage, and purslane extracts showed the highest inhibition of gall formation on tomato roots. Regarding reducing nematode numbers in the soil, the greatest effect was related to 1000 ppm water extract of fenugreek and purslane. However, they did not significantly differ significantly from other plants using the same concentration. The results of the laboratory studies showed the positive effects of water, ethanol, and acetone extracts of four medicinal plants, including fenugreek, lavender, borage, and purslane, on the prevention of egg hatching and the mortality of instar larvae of root-knot nematodes. The evaluation of the growth and development indicators showed that in fenugreek extract, a few galls were observed on roots, and the formation of galls was greatly reduced. After fenugreek, the lavender, borage, and purslane extracts showed the highest gall formation inhibition on tomato roots, respectively. The obtained data showed that fenugreek extract positively affected root-knot nematode decrease, and lavender, borage, and purslane extracts were in the next ranks, respectively.

Gray mold is one of the most important pathogens of cherry fruit. In the present study, the ability of bioinhibition of Botrytis cinerea by antagonist bacteria and the effects of adding marjoram essential oil  on the growth of pathogenic fungi was evaluated. According to the results, with increasing in the concentration of essential oil, the growth rate of fungi decreased. In vivo, cherry fruits were infected with a suspension of 105 hg/ml of pathogenic fungus, then separately treated with a suspension of 108 cells/ml of selected strains of antagonist bacteria and marjoram essential oil at 5 levels. The qualitative parameters were examined at three times of zero, 15 and 30 days. The results showed that the treatment of Bacillus bacterium and marjoram essential oil at a concentration of 750 μl/l were the most effective treatment to increase the level of antioxidant activity and phenylalanine-ammonialyase enzyme activity. Total phenol content and anthocyanin content at the concentration of 1000 μl/l  were the highest after 30 days. The highest amount of polyphenol oxidase enzyme was recorded after 15 days at the concentration of 750 μl/l. According to the results of this study, the mechanism of B. subtilis and marjoram essential oil in the control of gray mold of cherries is probably due to the induction of resistance in cherry fruit and increased antioxidant activity.

The objective of this study was to investigate the antifungal effects of liquid smoke from tobacco waste on three plant pathogenic fungi and identification and measurement of compounds effective on the antifungal properties of liquid smoke. The waste was pyrolyzed in furnace in the absence of oxygen, and smoke was converted to liquid smoke by refrigerant. Antifungal effects of liquid smoke were tested against Sclerotinia sclerotiorum, Rhizoctonia solani and Phytophthora nicotianae causing tobacco sore shin, collar rot and black shank disease agents, respectively. Six concentrations of the liquid smoke 0, 250, 500, 1000, 2000 and 4000 ppm were prepared and mixed with culture medium. The results of variance analysis showed that the effect of liquid smoke, concentration and the interaction of liquid smoke on concentration in limiting the fungal growth were significant at 1% probability level. Mean comparison of the effect of liquid smoke on these fungi showed that liquid smoke of 25% midrib + 75% scrap pyrolysis in 4000 ppm concentration had 100 percent mycelial growth control on the above fungi. In addition, the liquid smoke pyrolysis of above treatment in low concentrations caused 100 percent mycelia growth control of Rhizoctonia and Sclerotinia. According to research reports, the presence of phenolic compounds, organic acids and alkaloids constituents in liquid smoke is an agent of antifungal effects. Therefore, extraction of these constituents from liquid smoke was carried out and qualitative analysis was done by gas chromatography and mass spectrometry (GC/MS) and quantitative analysis of total phenol and alkaloids was done by spectrophotometer method. The results of this research showed that the effects of alkaloids constituents on the control of fungi were more than phenolic and organic acids constituents in liquid smoke from tobacco waste. The results showed the high potential of the liquid smoke of pyrolysis to be used as a biological control of pathogenic fungi.

Root-knot nematodes are one of the most important plant parasitic nematodes. The damage of these nematodes on tomatoes is estimated about 20-30%. One of the latest methods for controlling pests and plant diseases is application of organic products and use of natural ingredients with microbial and herbal origin. In order to reduce the damage of root-knot nematode in tomato plants, the nematicidal effects of aqueous extract of oak (Quercus branti L.) were evaluated on root-knot nematode, Meloidogyne javanica in vitro as well as in greenhouse conditions. An experiment was conducted in a completely randomized design. The treatments consisted of 1- plant parts (leaf and fruit) 2- plant extracts (at five concentrations, 1%, 2%, 3%, 5% and 7% for laboratory tests, and 0.05%, 0.1%, 0.15%, 0.25% and 0.35% (g dry powder in 100 grams of soil) for greenhouse experiments). Extracts of different parts of both tested plants caused maximum mortality of the second stage larvae, at the rates of 5% and 7%. Leaf and fruit extract at the rate of 7% caused 100% larval mortality. In case of reproduction factor, none of treatments had hazardous effect on plant growth including root and shoot length, fresh and dry weight. Between all treatments, the best treatment was identified at the rate of 0.35%, which was effective enough against nematode and also had no harmful effect on the tested plant.