Volume 15, Issue 3 (10-2012)
Abstract
Objective: Aflatoxin is important in the food industry, in animal husbandry and the medical area; there are enormous negative economic impacts due to this toxin. Numerous studies have researched extracts and plant compounds with the intent to reduce the growth of aflatoxin-producing organisms, inhibit toxin production and suppress the major toxin encoded genes (i.e., aflR) in these organisms. Licorice is an important plant in traditional medicine that possesses numerous antimicrobial activities. There is no report regarding the effects of licorice or its mechanism of action on the aflatoxin-producing Aspergillus species. The present study focuses on the inhibitory effects of licorice extract on aflR gene expression and the growth and survival of Aspergillus parasiticus (A. parasiticus). Methods: After the culture of A. parasiticus in toxin-inducer medium, we measured the minimal inhibitory concentration (MIC) for licorice extract. The aflatoxin concentration in the control and treated media was determined by HPLC. After harvesting the fungi from the toxin-inducing medium, its mRNA was extracted and cDNA synthesized by universal primers. The quantitative change in the aflR expression was analyzed via real-time PCR. Statistical analysis was performed by SPSS (v16). Results: The production of fungal mycelium decreased with increasing concentrations of licorice extract. The highest inhibitory concentration observed was 500 mg/ml of the extract. HPLC analyses revealed that the 10 mg/ml concentration of licorice extract inhibited toxin production by 99.9%. At this concentration, aflR gene expression was suppressed up to 40% as documented by quantitative RT-PCR analysis. Conclusion: Overall we concluded that the Licorice extract could inhibit the aflR gene expression and consequently the aflatoxin production efficiently in the A. parasiticus.
Volume 22, Issue 1 (1-2020)
Abstract
The bird cherry-oat aphid, Rhopalosiphum padi (L.) (Hemiptera: Aphididae), is a serious pest of Poaceae plants, especially wheat and corn, in the world and in Iran. In this study, the demographic parameters of R. padi were determined at seven constant temperatures (8.5, 15, 20, 25, 27.5, 29 and 31±0.5 °C), 65±5% RH, and 14:10 (L: D) photoperiods on Zea mays L., KSC704 cultivar. The total lifespan, from birth to death, decreased with increasing the temperature from 8.5 to 29 °C, but the nymphal stage duration increased a little at 29 °C. The highest value of life expectancy (ex) was observed at 8.5 °C and at 31 °C, the nymphs died before reaching the adult phase. The percentage of survival for nymphal stages was highest at 15 and 25 °C, and the net reproductive rate (R0=23.671 female/generation) had the highest value at 15 °C. The intrinsic rate of increase (rm) and the finite rates of increase (λ) increased at the temperature interval of 8.5 to 25 °C. At this range, the doubling time (DT) and the mean generation time (T) decreased as the temperature increased. According to the highest value of rm (0.22 day-1) and λ (1.134day-1) and also the lower value of T (9.095 d) and DT (2.16 d), the temperature of 25 °C was determined as the optimal temperature and the data showed that the proper temperature range for growth and reproduction of this aphid was between 15-25 °C. The effect of temperature on reproduction, especially the intrinsic rate of increase (rm), of R. padi would be useful for predicting its long-term population fluctuation over several generations and establishing integrated pest management (IPM) strategies against this pest.
