چكيده فارسي :
شته مومی كلم (Brevicoryne brassicae) و شته سبز گندم (Schizaphis graminum) به¬ترتیب از آفات مهم كلزا و گندم می¬باشند كه بصورت قابل توجهی زراعت این محصولات را از طریق تغذیه بصورت مستقیم و انتقال عوامل بیماریزای ویروسی بصورت غیر مستقیم كاهش می¬دهند. پیدایش مقاومت به سموم شیمیایی و اثرات حاد و مزمن ناشی از كاربرد آن¬ها باعث استفاده از تركیبات ثانویه گیاهی بصورت عصاره و اسانس به¬منظور كنترل آفات شده است. از جمله این تركیب¬ها می¬توان به عصاره میوه زیتون تلخ و پوست لیموترش اشاره كرد. در این تحقیق اثر دو عصاره اتانولی مذكور در سه غلظت متفاوت (10، 50 و 80 میكروگرم بر میلی¬لیتر) روی درصد تلفات شته مومی كلم و شته سبز گندم مورد بررسی قرار گرفت. نتایج نشان داد كاربرد عصاره اتانولی میوه زیتون تلخ در غلظت 80 میكروگرم بر میلی¬لیتر پس از 36 ساعت باعث 100 درصد مرگ و میر روی شته¬ها می¬شود كه در مقایسه با عصاره پوست لیموترش به¬طور معنی¬داری بیشتر بود. همچنین در این مطالعه، مقدار فنل كل در عصاره میوه زیتون تلخ (74/2 میلی¬گرم بر گرم وزن تر) نسبت به عصاره پوست لیموترش (79/1 میلی¬گرم بر گرم وزن تر) بیشتر بوده است كه می¬تواند با اثر كشندگی بالاتر زیتون تلخ روی این شته¬ها در ارتباط باشد. نتایج این تحقیق می¬تواند در كنترل شته¬های مذكور برای تولید محصولات سالم و ارگانیك مفید باشد.
چكيده لاتين :
Introduction: Wheat (Triticum aestivum L.) is the most principal plant food for 35 percent of the world 's population, and canola (Brassica napus L.) is one of the most important brassicaceous crops that play a major role in the development of edible oil. The greenbug, Schizaphis graminum (Rondani) and cabbage aphid, Brevicoryne brassicae (L.) are the main pests of wheat and canola, respectively, which can considerably limit profitable production of these crops either through direct feeding or via transmission of plant pathogenic viruses. Although chemical control is the most effective and easiest way to control aphids, but this method causes problems such as pesticide residues in food and environment, and development of resistance to insecticides. The utilization of plant extracts is an environmentally safe method that can be used in control of these aphids. Among these, the products of the Melia seed (Melia azedarach Linnaeus) and lemon peel (Citrus limonum Risso) can be noted. Negative associations between phenolic compounds present in plant species and aphid’s invasion have been recorded for some aphid species. In this study, our goal was to determine the amount of phenol in plant extracts of Melia seed and lemon peel and evaluate the toxicity of these compounds on the wheat aphid and cabbage aphid in various doses after different time periods.
Materials and methods: This research was conducted in a growth chamber (temperature 25 ± 1˚C, 65± 5% RH and a photoperiod of 16L: 8D). S. graminum and B. brassicae were bred on wheat (Pishtaz cultivar) and canola (Hyola401 cultivar), respectively. The extraction of Melia seed and lemon peel was carried out and then contact toxicity bioassay was done to evaluate the insecticidal effects of these extracts on nymphs of wheat and cabbage aphids using a completely randomized design. The leaves of wheat and canola plants, impregnated with three different concentrations of each extract (10, 50 and 80 g/ml) and dried. Thereafter the leaves were individually placed on agar gel 7.0% in Petri-dishes with a diameter of 6 cm. Then same age nymphs of wheat and cabbage aphids were separately released in Petri-dishes (20 aphids in each Petri-dish), and the number of dead nymphs was recorded after 12, 24 and 36 hours. This experiment was performed in three replicates for each treatment. Furthermore, the amount of phenolic compounds in two extract samples (Melia seed and lemon peel) was determined by Folin ciocalteu method, and the absorbance was measured at 725 nm using a spectrophotometer. The lethal effects of two tested extracts for each of aphid species (in each tested concentration and time period) were analyzed using T-test in SPSS v22 software. Variables of the mortality percent in three different concentrations and amount of total phenolic were evaluated using the one-way analysis of variance in SPSS. The comparison of differences between treatments means was done using Tukey’s test (P <0.05).
Results and Discussions: The results indicated that extract of Melia seed at the concentrations of 50 and 80 g/ml had a significantly higher mortality rate on both species of aphids compared with lemon peel after 12 and 24 hours. Also, Melia ethanolic extract at the concentrations of 80 g/ml after 36 hours, caused 100% mortality on two aphid species, which was significantly higher compared with extract of lemon peel. This could be due to differences in the amount of secondary compounds such as total phenolic. In the present study, the amount of total phenolic compounds was higher in extract of Melia (2.74 mg・g-1 FW) in comparison with lemon peel (1.79 mg・g-1 FW) that was associated with more lethal effects of Melia extract on the aphids. Based on the results, different concentrations of studied extracts had significant effects on the percentage of mortality of wheat and cabbage aphis. Comparison of the insecticidal effects of different concentrations showed an increase in mortality of aphids by increasing the concentration. In addition, the percentage of mortality of wheat aphids was higher than on cabbage aphids. That is probably due to the external waxy surface of the body of B. brassicae.
The research could provide valuable information for control of S. graminum in the wheat fields and B. brassicae in canola fields and thus can be useful for the production of healthy and organic crops.
