| چکیده انگلیسی مقاله |
Extended Abstract
Introduction and Objectives: One of the goals of the new programs for silkworm breeding is to investigate the ability to withstand environmental fluctuations. Silkworms are cold-blooded organisms, meaning that their body temperature and metabolic processes are affected by the temperature of the environment. Silkworms are sensitive to temperature changes and exposure to cold temperatures can affect their growth, development and overall health. So far, no special attention has been paid in the field of improving compatibility traits in Iranian silkworms. The requirement of this goal is to improve the traits related to resistance to stresses and adaptation to new conditions. In this regard, the country's silkworm gene bank should be expanded, especially in the field of commercial lines, and while identifying the genetic capabilities of the existing lines, new genetic resources should also be made available. In the meantime, producing eggs that are resistant to cold stress is one of the proposed solutions to deal with this stress. For this purpose, it is necessary to determine the level of resistance or susceptibility to cold stress in commercial lines used in the production of commercial eggs, and the desired lines should be rated from this aspect. With this rating, recommendations can be made to create crosses between the mentioned lines with the aim of producing commercial eggs resistant or sensitive to cold stress and distributing each batch of these eggs in different geographical areas with different climates. In the present study, the performance of commercial lines of Iranian silkworms including 31, 32, 103, 104, 151, 153, and 154 under cold stress was investigated in the form of control and challenge treatments.
Material and Methods: After the steps of preparation for breeding, the silkworm eggs were kept in the hatching room under standard temperature and humidity conditions for 12 days. For breeding, the standard conditions of 25±2 degrees Celsius, relative humidity of 75±5% and photoperiod of 16 hours of light and 8 hours of darkness were considered. Mulberry leaves of modified varieties were used to feed the larvae. To induce cold stress, 300 larvae on the third day of the fifth instar (in the form of 3 replicates of 100 larvae) were placed in an incubator at 0oC for 12 hours and then returned to the standard rearing conditions at 25 degrees. For investigation of the production traits in each of the cold stress and control treatments, the characteristics of cocoon weight, cocoon shell weight, cocoon shell percentage, number of cocoons per liter, cocoon weight per liter, the average weight of a cocoon, the average weight of a best cocoon, the average weight of a middle cocoon, the average weight of a weak cocoon and the average weight of a double cocoon and some traits related to longevity, including the percentage of live larvae, the percentage of dead larvae, the percentage of pupal losses and the percentage of produced butterflies were investigated. For statistical analysis, the generalized linear model (GLM) procedure was used in SAS software, and comparison of means was performed with Tukey's statistical test with a significant level of 0.05.
Results: In general, the highest and lowest values of traits among genotypes and under applied stress conditions were not the same, but some genotypes have higher performance for a larger number of traits. Among the studied traits, traits related to cocoon weight, cocoon shell weight and cocoon shell percentage are the most important traits for breeding purposes, which have high economic value and are used to improve cocoon performance. Meanwhile, the traits of live and dead larvae percentage along with death pupae percentage and productive moth percentage are important indicators related to viability and showed a significant difference between the studied lines. The results of comparisons of mean showed that in general, the larvae of the control group had better performance in all the examined traits compared to the larvae under cold stress and a significant difference was observed between them (P<0.001). However, two lines 153 and 154 from the cold stress group had higher performance in many production and longevity traits than other lines under cold stress and even some lines of the control group.
Conclusion:
Temperature of the breeding environment is one of the factors that, in case of fluctuation, leads to the deviation of breeding conditions from the optimal state and damage. In general, in insects, cold stress and low temperatures have different effects, considering the intensity and duration of the insect's exposure, and in addition, the stage of life and the degree of evolution of adaptation mechanisms and adaptation to the environment also have a major effect on the insect's response to cold stress. The results of the present research show that the performance of commercial lines of Iranian silkworms is affected under cold stress conditions and lines 153 and 154 have higher resistance than other lines and they can be prioritized in the production of commercial hybrids in terms of resistance to cold stress and production and survival records. For further studies, it is suggested to measure the molecular and biochemical characteristics of some proteins related to temperature stress in different treatments.
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| نویسندگان مقاله |
شیوان زمانی | Sheyvan Zamani
Department of Plant Medicine, Faculty of Agricultural Sciences, Gilan University, Rasht, Iran
دانشکده علوم کشاورزی، دانشگاه گیلان، رشت، ایران
جلال جلالی سندی | Jalal Jalali Sendi
Department of Plant Medicine, Faculty of Agricultural Sciences, Gilan University, Rasht, Iran
دانشکده علوم کشاورزی، دانشگاه گیلان، رشت، ایران
فرجاد رفیعی | Farjad Rafeie
Department of Agricultural Biotechnology, Faculty of Agricultural Sciences, Gilan University, Rasht, Iran
گروه بیوتکنولوژی کشاورزی، دانشکده علوم کشاورزی، دانشگاه گیلان، رشت، ایران
رامین عبدلی | Ramin Abdoli
Iran Silk Research Center, Agricultural Research, Education and Extension Organization, Gilan, Rasht, Iran
مرکز تحقیقات ابریشم کشور، سازمان تحقیقات، آموزش و ترویج کشاورزی، گیلان، رشت، ایران
وحید رحیمی النگی | Vahid Rahimi Alangi
Department of Plant Medicine, Faculty of Agricultural Sciences, Gilan University, Rasht, Iran
گروه گیاه پزشکی، دانشکده علوم کشاورزی، دانشگاه گیلان، رشت، ایران
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