چکیده:
با توجه به ضرورت ذخیره سازی کارآمد زنبور پارازیتویید Bracon hebetor Say در انسکتاریوم ها، این پژوهش با هدف ارزیابی تاثیر تعداد دفعات تغذیه از مادهی قندی (در سه سطح بدون تغذیه، یک نوبت تغذیه پیش از ذخیرهسازی در یخچال و دو نوبت تغذیه پیش و در حین ذخیرهسازی) و وضعیت جفتگیری (در دو سطح جفتگیری کرده و بدون جفتگیری) بر مقاومت حشرات کامل مادری و نتاج نسل بعد این زنبور به سرما (دمای 1±5 درجهی سلسیوس) انجام گردید. تغذیه ی حشرات کامل زنبور از مادهی قندی و جفتگیری آنها پیش از ذخیرهسازی در یخچال موجب کاهش تلفات ناشی از سرما و افرایش تخمگذاری در مقایسه با زنبورهای گرسنه و جفتگیری نکرده شد. بیشترین تلفات ناشی از سرما در زنبورهای ماده (2/33 درصد) در جمعیت هایی مشاهده شد که بدون انجام تغذیه و جفتگیری به مدت دو هفته درون یخچال ذخیره شدند و در مقابل، کمترین تلفات (71/7 درصد) در زنبورهای مادهی جفتگیری کرده ای مشاهده شد که با دو نوبت تغذیه به مدت یک هفته ذخیرهسازی شدند.تغذیه زنبورهای مادری از مادهی قندی همچنین موجب کاهش تلفات مراحل نارس زنبور و کوتاه تر شدن طول دورهی نشوونمای آنها در نسل بعد شد.میانگین تلفات و طول دورهی نشوونمای مراحل نارس در زنبورهای تغذیه شده از ماده قندی (به ترتیب، 82/22 درصد و 17/11 روز) به طور معنی داری از زنبورهای تغذیه نشده (به ترتیب، 64/30 درصد و 77/11 روز) کمتر بود (آنالیز اُرتوگنال). به طور کلی، با توجه به اثرات مثبت تغذیه و جفتگیری، توصیه میشود برای ذخیرهسازی موثر این زنبور در دمای یخچال از زنبورهای جفتگیری کرده ای استفاده شود که پیش از ذخیرهسازی حداقل یک نوبت با آب عسل تغذیه شده باشند.
چکیده انگلیسی:
Background and Objectives Bracon hebetor Say is a well-known cosmopolitan ectoparasitoid that attacks the larvae of various lepidopteran pests, especially cotton boll worm, Helicoverpa armigera. Cold storage is a general technique for long-term preservation of this parasitoid in insectaries. Most parasitoids require sugar supplemental sources as a source of energy in adult stage. Because of the need to enhance cold storage efficacy in commercial insectaries, this study was carried out to assess effects of feeding frequencies and mating status on biological and reproductive characteristics of maternal wasps and their progeny (F1) stored in refrigerator (5±1˚C) for two durations of 7 and 14 days. Materials and Methods B. hebetor reared on the 4-5 instars larvae of Anagasta kuehniella in a climate-controlled room, at 26 ± 2˚C, 50±5% RH, and a 16:8 (L:D)h. photoperiod. The effect of feeding frequency was studied in three levels of "without feeding" (starved wasps), "one-time feeding" before cold storage, and "two-time feedings" (before and during cold storage). Mating status was investigated in two "mated" and "unmated" levels. After each treatment, adult parasitoids were stored inside a refrigerator (5±1˚C) for two periods of 7 and 14 days, and mortality, longevity and fecundity of maternal parasitoids were subsequently assessed. Immature’s developmental time and mortality, percentage of adult emergence and sex ratio were also investigated for progenies in next generation. The experiment was carried out using a factorial experimental design and obtained data were analyzed using SAS software, and LSD mean comparison test. Results Results showed that sugar feeding and mating of parasitoid before beginning of cold storage decreased mortality during storage and increased fecundity compared to starved and unmated wasps. The highest mortality of females (33.2%) was observed in starved and unmated wasps that were stored in refrigerator for 14 days. In contrast, the lowest mortality of females (7.71%) belonged to mated parasitoids that fed twice (before and during cold storage) on honey solution and stored for 7 days. Feeding on honey solution by maternal adult parasitoids reduced immature’s mortality and their developmental time in progenies of next generation. Means of immature’s mortality and developmental time in fed wasps (22.82 percent and 11.17 days, respectively) were significantly lower than starved ones (30.64 percent and 11.77 days, respectively). Discussion According to our results, feeding on honey solution increased cold-tolerance of both male and female B. hebetor adults. So that, honey-fed adult parasitoids had lower mortality and higher fecundity than starved ones. Similar to feeding, our results showed that mated parasitoids had higher survival and fecundity than unmated ones. Also, feeding and mating of cold-stored maternal parasitoids had a positive effect on the survival and development of progenies in next generation. In conclusion, spraying honey solution on the rearing cages of B. hebetor and providing sufficient time for mating before storing in refrigerator, are recommended to improved cold-storage efficacy of this parasitoid in insectaries.
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