چكيده فارسي :
شته مومي كلم (Brevicoryne brassicae) و شته سبز گندم (Schizaphis graminum) به ترتيب از آفات مهم كلزا و گندم مي باشند كه بصورت قابل توجهي زراعت اين محصولات را از طريق تغذيه بصورت مستقيم و انتقال عوامل بيماريزاي ويروسي بصورت غير مستقيم كاهش مي دهند. پيدايش مقاومت به سموم شيميايي و اثرات حاد و مزمن ناشي از كاربرد آن ها باعث استفاده از تركيبات ثانويه گياهي بصورت عصاره و اسانس به منظور كنترل آفات شده است. از جمله اين تركيب ها مي توان به عصاره ميوه زيتون تلخ و پوست ليموترش اشاره كرد. در اين تحقيق اثر دو عصاره اتانولي مذكور در سه غلظت متفاوت (۱۰، ۵۰ و ۸۰ ميكروگرم بر ميلي ليتر) روي درصد تلفات شته مومي كلم و شته سبز گندم مورد بررسي قرار گرفت. نتايج نشان داد كاربرد عصاره اتانولي ميوه زيتون تلخ در غلظت ۸۰ ميكروگرم بر ميلي ليتر پس از ۳۶ ساعت باعث ۱۰۰ درصد مرگ و مير روي شته ها مي شود كه در مقايسه با عصاره پوست ليموترش به طور معني داري بيشتر بود. همچنين در اين مطالعه، مقدار فنل كل در عصاره ميوه زيتون تلخ (۲/۷۴ ميلي گرم بر گرم وزن تر) نسبت به عصاره پوست ليموترش (۱/۷۹ ميلي گرم بر گرم وزن تر) بيشتر بوده است كه مي تواند با اثر كشندگي بالاتر زيتون تلخ روي اين شته ها در ارتباط باشد. نتايج اين تحقيق مي تواند در كنترل شته هاي مذكور براي توليد محصولات سالم و ارگانيك مفيد باشد.
چكيده لاتين :
Introduction: Canola (Brassica napus L.) and wheat (Triticum aestivum L.) are the most principal crops that
play a major role in the development of edible oil and world's population food, respectively. The greenbug,
Schizaphis graminum and cabbage aphid, Brevicoryne brassicae, are the main aphid pests of wheat and canola,
respectively. They can restrict considerably the production of these crops 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 makes problems such as pesticide residues in food and the environment and
increase insecticide - resistance in aphid populations to. The utilization of plant extracts is an environmentally
safe method that is used in the control of these aphids. Among these, the products of Melia fruit (Melia
azedarach Linnaeus) and lemon peel (Citrus limonum Risso) can be noted. The negative relevance between
phenolic compounds present in plant species and aphid invasion has been recorded in some aphid species. Our
goal in this study was to assess the toxicity effects of Melia fruit and lemon peel extracts on wheat and cabbage
aphids and the determination of the amount of total phenol in these plant extracts.
Materials and Methods: This research was conducted in a growth chamber (temperature 25 ± I'C, 65± 5%
RH and a photoperiod of 16L: 80). Schizaphis graminum and B. brassicae were reared on wheat (Pishtaz
cultivar) and canol a (Hyola40 1 cultivar), respectively. The extraction of Melia fruit and lemon peel was
prepared. Then the contact toxicity bioassay was done to evaluate the insecticidal effects of these extracts on
wheat and cabbage aphids based on completely randomized design. The leaves of wheat and canola plants was
treated by one microliter sampler using topical method. In this study, three different concentrations of each
extract ( 10, 50 and 80 ~g/ml) was applied. Thereafter the leaves individually were placed on agar gel 0. 7% in
Petri-dishes with 6 centimeter diameter. After that, the same instars of S. graminum and B. brassicae were
released in Petri-dishes (20 aphids in each Petri-dish) separately. The number of dead nymphs was recorded after
12, 24 and 36 hours after releasing. This experiment was performed for each treatment in three replications.
Furthermore, the amount of phenolic compounds in two extract samples (Melia fruit and lemon peel) was
determined by Folin Ciocalteu method, and the absorbance was measured at 725 nm by Spectrophotometer. So
that the amount of !50 g of each plant powder was mixed in an Erlen which contained 500 ml of ethanol 90%.
The lid of Erlen was sealed with parafilm and after 5 minutes mixing, the contents of the Erlen were kept in the
refrigerator inside an aluminum foil for 24 hours to avoid them from exposure to light. After the time, the plant
extract was separated by filter paper and after several hours, evaporation of the solvent was performed under
laboratory hood to provide pure extract. The solid extract was stored in a refrigerator for a short time at 4 o C.
For each test, the extract was diluted with distilled water and the concentrations were prepared. The lethal effects
of two tested extracts for each of aphid species (in each tested concentration and time period) were analyzed
using T-test using S·PSS v22 software. Variables of the mortality percent in three different concentrations and
amount of total phenolic compound were evaluated by one-way analysis of variance. The comparison of
differences between treatments means was performed using Tukey's test (P<0.05).
Results and Discussions: The results indicated that the extract of Melia fruit in 50 and 80 ~g/ml
concentrations had significantly higher mortality rate on both the species of aphid compared with that in the
lemon peel, after 12 and 24 h. Also, ethanolic Meliae extract in 80 ~g/ml concentration after 36 h, caused I 00%
mortality on two aphid species, which was significantly higher than that in the lemon peel extract. This could be
due to differences in the amount of secondary compounds such as total phenol content. In the present study, the
amount of total phenolic compounds was higher in Melia extract (2.74 mg · g-1 FW) in comparison with lemon
peel (1.79 mg • g-1 FW), indicatingmore sustainable of the aphids to the lethal effects of Melia extract. Based on
the results, the different concentrations of the extracts had significant effects on mortality percentage of the
wheat and the cabbage aphids. Comparison of the effect of the different concentrations of the insecticides
showed that mortality of the aphids were dose- related. In addition, the mortality percentage of the wheat aphids
was higher than the cabbage aphids, probably due to the presence of wax on the surface of B. brassicae body.
This research could provide valuable information for the production of healthy and organic crops using nonchemical
control of S. graminum in wheat fields and B. brassicae in canola fields.
