جستجوی مقالات مرتبط با کلیدواژه « bioassay » در نشریات گروه « زراعت »

Saffron or red gold is a strategic agricultural product with a very high non-oil export potential. Considering the ban on the use of synthetic chemical poisons against saffron pests and the growing trend of planting this product in the country, as well as the importance of producing certified seeds of agricultural products, it is inevitable to find non-chemical ways to control the pest and produce certified saffron onions. Meanwhile, the saffron mite Rhizoglyphus robini Claparède is one of the most important pests of saffron, which causes great damage to onions and saffron crops every year. In the present study, the toxicity of four plant essential oils from the Asteraceae family, including Artemisia sieberi Besser, Acroptilon repens (L.), Cichorium intybus L. and Achillea millefolium L., was evaluated on the adult female species of the saffron mite in laboratory conditions. Bioassay was performed by fumigation method inside a 5 cm petri dish in total darkness, with a relative humidity of 70% and a temperature of 26 degrees for 24 hours. For each essential oil, 6 concentrations and 3 repetitions were considered for each concentration. The results of the bioassay by fumigation method showed that the essential oil of A.sieberiwith LC50 = 160.09 ppm has the highest and C. intybus essential oil with LC50 = 440.12 ppm has the lowest toxicity on saffron bulb mite. Also, the highest concentration slope was observed in A. repens essential oil (5.801±0.719) and the lowest was observed in the essential oil of A. sieberi and A. millefolium. Based on the starting point of toxicity, the essential oil of A. sieberiwith the highest intercept (-2.177±0.323) caused the fastest initial toxicity on bulb mite at a concentration of 33.21 ppm.

One of the negative effects of herbicide residuals is their phytotoxicity on subsequent susceptible crops in rotation. In order to study the phytotoxic residue effects of triasulfuron +dicamba (Lintur® WG70%) on 12 rotational crops, four experiments were carried out at field research stations of Khorasan razavi (Mashhad), Khuzestan (Ahwaz), Fars (Darab) and Golestan (Gonbad-Kavous) provinces in Iran. Rotational crops were planted in sprayed plots (with 170 g Lintur®) or in control plots (without spraying) immediately after wheat harvesting (as second crop) or in autumn. The rotational plants were selected from the summer crops including maize, cotton, mung bean, sesame and soybean, and fall crops including sugar beet, canola, clover, wheat, barley, faba bean and green pea. Results of t-student test showed the significant negative effect of triacsulfuron+dicambba residues on maize at Mashhad, Ahwaz and Darab in terms of root and shoot dry weight and yield (14.6 to 63% yield reduction). Damage to mung bean was significant in Ahwaz and Gonbad (5.6% -29% yield loss). Sesame yield in Ahwaz decreased 46% and soybean and green pea yields in Gonbad decreased by 12% and 16%, respectively. Rapeseed yield was damaged only in Ahwaz (31%) but in Mashhad, Darab and Gonbad the herbicide damage was not significant. Autumn planted sugar beet was significantly damaged in Ahwaz (46% yield) and in Gonbad (5%). The interval between herbicide application and emergence of summer crops was 90-146 days and for autumn crops was 222-311 days, depending on the rotational plants and experimental regions. Herbicide residue of triasulfuron + dicamba did not have significant damage on cotton, clover, wheat, barley and faba beans in related experiments.

Pink stem borer, Sesamia creticaLed, is one of the most important pests of sugarcane and maize in Iran. Insecticidal properties of essential oils of four cumin ecotypes, namely Fars-Sivand (FS), North Khorasan-Shirvan (KS), Kerman-Kuhbanan (KK), and Kerman-Rafsanjan (KR), has been evaluated against 4th instar-larvae of S. cretica in a completely randomized design with four replications. Larval mortality at 27±2 °C, relative humidity of 65±5%, and 16:8 hours light: darkness period is recorded after 72 hours. Results show that all cumin ecotypes have been toxic to the pest, with the lowest LC50 value, obtained from the essential oil of KR ecotype (2725 ppm) followed by KK, FS, and KS ecotypes (2777, 3099, and 8390 ppm, respectively). The chemical analysis of essential oils tested by GC-MS shows that m-cymene in the KR ecotype has been higher than other cumin ecotypes. Therefore, the high toxicity of KS ecotype compared to other cumin ecotypes can be related to the presence of such compounds. According to the present study’s results, the essential oils of cumin ecotypes are potentially a great substitute for chemical insecticides in the integrated management of S. cretica.

Nowadays, herbicides are crucial for modern agricultural systems. Yet, improper application of herbicides will have dangerous consequences. For example, there will be crop damage due to long lasting herbicide residue or herbicide drift on neighbor crops if applied on non-target species. The purpose of this experiment was to determine the sensitivity of wheat and barley to pendimethalin residue by using bioassay.

In order to evaluate soil residue of pendimethalin, experiments with completely randomized designs were carried out in the greenhouse at Faculty of Agricluture and Natural Resources of Gonbad Kavous University. In this experiments, different doses of pendimethalin (0, 1, 5, 10, 15, 20, 30, 40, 50, 75 and 100 % of recommended dose) were applied on wheat and barley in order to measure the dry weight of root and shoot of crops. The concentration of herbicides was made by dilution of stock solvent. Three/four-parameter log-logistic curves were used for fitness of the data.

Results indicated that almost all data followed the three-parameter logarithm logistic curve. Results of separate fitness of data showed that the residue of pendimethalin always caused reduction of dry weight of the evaluated crops. Fifty percent reduction of shoot dry weight of wheat and barley was obtained from 400.5 and 623.05 g.a.i.ha-1 of pendimethalin and the ED50 values of root dry weight of wheat and barley were 65.88 and 269.66 g.a.i.ha-1 of pendimethalin, respectively.

Generally, the results of simultaneously fitted data shows that wheat is always more sensitive to pendimethalin rather than barley. Based on results, even the very little portion of herbicides can cause damage to crops, thus, considering the sensitive crop in rotation is so important since this residue can stay active even in two-season crops and make crop injuries. The selection between 3 and 4 Logarithm logistic model was based on: 1. Lack of fit test significance 2. Significance of estimated parameters, especially the parameters and the way of distribution of data around the curve (graphical observation).

Interference includes competition for environmental potentials and allelopathy. By releasing chemical compounds, usually of secondary metabolites, in various ways such as root exudation, decomposition, leaching and volatilization, allelopathic weeds may have positive, negative or even neutral effects on crops. Therefore, the purpose of this experiment was to evaluate the hetrotoxic potential of Sorghum halepense, Portulaca oleracea and Centurea depressa in characteristics of germination, chlorophyll content and carotenoid pigments of cress under laboratory conditions.

For bioassay experiments, various concentrations of 0, 20, 40, 60, 80 and 100% of the weeds such as S. halepense, P. oleracea and C. depressa were prepared with the help of distilled water and were subsequently separately applied on 50 certified seeds of cress. In this experiment, characteristics such as rate and germination percentage, content of chlorophyll a, b, total chlorophyll content and carotenoids were measured based on the chilled acetone method.

Regression model showed that rate and germination percentage of cress significantly decreased at concentrations higher than 80% of S.halepense only. For every unit increase in the concentration, radicle length, seed vigor, content of total chlorophyll and carotenoids of cress decreased about 0.08 cm, 8.68, 0.007 mg/g and 0.007 mg/g, respectively. According to the results, there was an exponential relationship between different concentrations of the P. leracea extract with germination characteristics and photosynthesis pigments of cress so that in most cases, these characteristics up to concentration of 40% had moderate decline, but beyond this concentration, they showed a steep decline. In case of C. depressa, rate and germination percentage, as well as the shoot length of cress decreased about 14.67, 14.67 and 29.81% respectively, using only a concentration of 100%. However, radicle length and seed vigor of cress decreased with increased concentrations of aqueous extract of C. depressa. The most reductive effects were obtained in the treatment of 100%, which were about 52.38 and 55.44% respectively. Amount of total chlorophyll of cress decreased about 14.37, 27.59 and 25.29% respectively in concentrations of 60, 80 and 100% of C. depressa extract, as compared with the control. On the other hand, concentrations of 20 and 40% of C. depressa had no significant effect on the pigment studied. The result of carotenoids content was the same as total chlorophyll.

Based on the results, the weeds studied, especially P. oleracea, with high concentrations, had strong hetrotoxic effect on germination characteristics and photosynthesis pigments. This requires further investigation in a natural environment where targeted plants grow in close proximity.

Hetrotoxic compounds of Portulaca oleracea, especially in high concentrations significantly decrease seed germination and photosynthetic pigments of cress as compared with Sorghum halepense and Centurea depressa. Given the evidence for the hetrotoxic effect of aqueous extract of the weeds studied, they could be introduced as candidates for production of bio-herbicides.