فهرست مطالب

پژوهش های کاربردی زراعی - پیاپی 124 (پاییز 1398)
  • پیاپی 124 (پاییز 1398)
  • تاریخ انتشار: 1398/07/01
  • تعداد عناوین: 6
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  • محمدرضا عباسی*، عبداناصر مهدیپور، سید علیرضا بهشتی، حمید رضا شریفی صفحات 1-17

    استفاده از تنوع ژنتیکی در منابع گیاهان زراعی یکی از راه کارهای مهم در راستای کشاورزی پایدار است. به منظور شناسایی ژرم پلاسم های علوفه ای متحمل به سرما، تعداد 124 توده در قالب 40 گونه و 9 جنس از گیاهان علوفه ای یک ساله حاصل آزمایش های قبلی از جنس های شبدر(Trifolium spp)، یونجه یک ساله (Medicago spp)، اسپرس (Onobrychis spp)، ماشک (Vicia spp)، شبدر شیرین (Melilotus spp)، لولیوم (Lolium spp)، بروموس (Bromus spp)، خلر (Lathyrus cicero) و فالاریس (Phalaris tuberosa) انتخاب شده و در مزرعه پژوهشی ایستگاه تحقیقات کشاورزی و منابع طبیعی جلگه رخ (خراسان رضوی) در قالب آزمایش مقدماتی در سال 1395 مورد ارزیابی قرار گرفتند. در طی استقرار گیاه در زمین، صفات درصد رویش بذور در کرت، درصد پوشش سبز سطح کرت در پاییز و بهار، میزان رشد در پاییز و بهار، ارتفاع گیاه در گلدهی و تحمل به سرما ارزیابی گردید. وجود 68 روز یخبندان و کمینه دمای C° 4/17- نشان از وقوع تنش سرما داشت. نتایج تجزیه واریانس یک طرفه نشان داد که تفاوت معنی داری ازنظر صفات مورد ارزیابی بین جنس ها وجود دارد. جنس های لولیوم و بروموس از متحمل ترین نمونه ها در بین باریک برگ های علوفه ای و کل ژرم پلاسم ها بودند. در لگوم های علوفه ای جنس شبدر شیرین متحمل ترین جنس به تنش سرما بود. اگرچه جنس های ماشک، خلر و شبدر ایرانی قادر به تحمل سرما نبودند، ولی با توجه به تولید پوشش سبز مناسب تا قبل از وقوع سرما و حفظ این پوشش تا بهار سال بعد روی زمین ازنظر کشاورزی حفاظتی مفید بودند.

    کلیدواژگان: تنش سرما، لگوم های علوفه ای، باریک برگیان علوفه ای
  • سیدمحمدعلی مفیدیان*، جعفر احمدی، علی مقدم صفحات 18-39

    شناسایی واکنش فیزیولوژیک اکوتیپ های یونجه می تواند به درک بهتر در انتخاب رقم مناسب در شرایط کمبود آب منجر شود. بدین منظور این آزمایش در دو محیط جداگانه، شامل محیط بدون تنش آبی و تنش قطع آب به مدت 20 روز انجام شد. این پژوهش با 10 اکوتیپ سردسیری و گرمسیری یونجه و درسه تکرار در قالب طرح بلوک های کامل تصادفی در مزرعه موسسه تحقیقات اصلاح و تهیه نهال و بذر کرج طی سال های 97-1395 اجرا شد. در سال اول و دوم کمترین مقدار شاخص حساسیت به تنش به ترتیب با 0/35 و 0/51 مربوط به اکوتیپ های گرمسیری بغدادی و بمی بود که در بین اکوتیپ های مورد بررسی بالاترین مقاومت و یا کمترین افت عملکرد در برابر بی آبی 20 روزه را از نظر میانگین تولید ماده خشک نشان داد. در مجموع این پژوهش، اکوتیپ سردسیری KFA6 با پایداری غشا سلولی بالا،کمترین نشت الکترولیت ها به میزان 13/79 درصد وکمترین مقاومت روزنه ای با 23/69 ثانیه بر سانتی متر را داشت. همچنین اکوتیپ KFA6 بیشترین مجموع رنگیزه های فتوسنتزی را با 1/623 میلی گرم بر گرم وزن تر برگ داشت که منجر به تولید حداکثر عملکرد ماده خشک با رطوبت 13 درصد به میزان 17/48 تن درهکتار و برتری 14 درصدی ماده خشک در بین اکوتیپ ها و دو محیط آبیاری کامل و قطع 20 روزه آبیاری شد. نتایج این مطالعه نشان داد با استفاده از شاخص های فیزیولوژیک که معیاری نسبتا آسان، ارزان و سریع است، بطور موثری اکوتیپ با عملکرد مطلوب انتخاب می شود.

    کلیدواژگان: دمای کانوپی، مقاومت روزنه ای، پایداری غشا سلول، رنگیزه های فتوسنتزی و یونجه
  • بابک پیکرستان، ثریا کرمی*، طیبه بساکی صفحات 40-53

    به منظور بر رسی تاثیر تنش قطع آبیاری بر شش رقم ذرت شیرین (Merit, Chase, KSC.403, KSC.404, (Obsession, Basin در دو مرحله 8 برگی (S1) و پرشدن دانه، (S2) در مقایسه با آبیاری کامل (S0)، آزمایش کرت های خرد شده در قالب طرح بلوک کامل تصادفی با سه تکرار در مزرعه پژوهشی دانشگاه پیام نور استان مرکزی، واقع در میلاجرد اجرا گردید و صفات شاخص سطح برگ (LAI)، سرعت رشد محصول (CGR)، سرعت رشد نسبی (RGR)، سرعت جذب خالص (NAR) و عملکرد دانه اندازه گیری شد. بر اساس نتایج بدست آمده، بیشترین تنوع مشاهده شده بین الگوهای آبیاری مربوط به شاخص سطح برگ، سرعت رشد نسبی و عملکرد دانه بود و ترتیب نزولی S0>S2>S1 برای میانگین صفات اشاره شده، مشاهده شد (P<0.05). همچنین از نظر عملکرد دانه به عنوان مهمترین صفت اقتصادی، با اعمال تنش قطع آبیاری در S1 و S2 به ترتیب کاهش 84/20 و 08/7 درصدی در مقایسه با S0 مشاهده شد. از سوی دیگر ارقام Obsession و Basin بیشرین شاخص های رشد و کمترین افت عملکرد را در تیمارهای S2, S1 و S0 در مقایسه با سایر ارقام نشان دادند. در مجموع بر اساس نتایج حاضر شاید بتوان شاخص های LAI و RGR را برای شناسایی و انتخاب ارقام ذرت شیرین مقاوم به تنش قطع آبیاری در مراحل رشد رویشی و زایشی، پیشنهاد نمود. همچنین با توجه به محدودیت منابع آبی ، استفاده از الگوی قطع آبیاری در مرحله پرشدن دانه با افت ناچیز عملکرد دانه در ارقام ذرت شیرین بخصوص ارقام فوق شیرین Obsession و Basin در استان مرکزی، قابل توصیه است.

    کلیدواژگان: تنش خشکی، پر شدن دانه، مرحله 8، برگی ذرت شیرین
  • سحر کلاه کج، مهرو مجتبایی زمانی* صفحات 54-74

    به منظورتعیین سهم صفات موثر بر عملکرد دانه و شناسایی موثرترین صفات به عنوان شاخصی برای گزینش ارقام پر محصول در منطقه رامهرمز، این پژوهش در قالب طرح بلوک های کامل تصادفی با سه تکرار و ده ژنوتیپ بهاره کلزا (هایولا 401، هایولا420، هایولا308، هایولا4815، هایولا50، هایولا60، سان37، سان34، صفی6 و دلگان) در سال زراعی 96-1395 اجرا شد. ژنوتیپ های مورد مطالعه از نظر تمامی صفات مورد بررسی به استثنای موفقیت تبدیل گل به خورجین اختلاف معنی داری داشتند. هیبرید دیررس هایولا 60 با وجود تعداد خورجین در بوته زیاد، با کمترین تعداد دانه در خورجین و وزن هزار دانه نسبتا پایین، به دلیل برخورد مرحله دانه بندی با گرمای انتهای فصل، از کمترین عملکرد دانه برخوردار بود. صفی 6 با بیشترین تعداد خورجین در بوته، هایولا 420 با بیشترین وزن هزار دانه و تعداد دانه در خورجین نسبتا بالا و سان 34 با بیشترین تعداد دانه در خورجین، از بیشترین عملکرد دانه برخوردار بودند. در تجزیه رگرسیون گام به گام صفات تعداد دانه در خورجین، تعداد خورجین در شاخه های فرعی، وزن هزار دانه و ارتفاع پایین ترین خورجین از سطح زمین 71 درصد از تغییرات عملکرد را توجیه کردند. بر اساس نتایج تجزیه علیت، صفت تعداد دانه در خورجین با بیشترین تاثیر مستقیم مثبت بر عملکرد دانه و اثرات غیر مستقیم ناچیز از طریق سایر صفات، به عنوان شاخصی برای گزینش ژنوتیپ هایی با عملکرد بالا در برنامه های اصلاحی کلزای بهاره معرفی شد.

    کلیدواژگان: همبستگی، رگرسیون گام به گام، تجزیه علیت، تنوع ژنوتیپی
  • مجید جعفر اقایی*، امیرهوشنگ جلالی صفحات 75-88

    به منظور بررسی تاثیر سطوح مختلف شوری آب آبیاری بر تشعشع دریافتی و عملکرد برخی ژنوتیپ های پنبه، پژوهشی در سال 1392 با استفاده از آزمایش کرت های یک ‏بار خرد شده در قالب طرح بلوک های کامل تصادفی در چهار تکرار در ایستگاه تحقیقات شوری و زه کشی رودشت اصفهان انجام شد. تیمارهای آب آبیاری در سه سطح (4، 8 و 12 دسی زیمنس بر متر) کرت‏های اصلی و دو رقم تجاری ورامین و شایان به همراه 6 موتانت پنبه کرت‏های فرعی را تشکیل دادند. تاثیر تیمارهای شوری بر صفات تعداد غوزه در بوته و عملکرد وش در سطح 5 درصد از نظر آماری معنی دار بود اما تاثیر برهمکنش شوری و ژنوتیپ بر عملکرد و اجزای عملکرد از نظر آماری معنی دار نبود. بر اساس نتایج در هنگام صبح مقدار نور دریافت شده در مرکز سایه انداز در تیمارهای 12، 8 و 4 دسی زیمنس بر متر به ترتیب برابر329، 317 و 303 فوت کندل و در ظهر به ترتیب 358، 348 و 310 فوت کندل بود. عملکرد وش در تیمار 8 و 12 دسی زیمنس بر متر نسبت به تیمار 4 دسی زیمنس بر متر به ترتیب 16 و 3/20 درصد کاهش یافت. رقم شایان با عملکرد 2852 کیلوگرم وش بالاترین مقدار عملکرد را تولید کرد اما تفاوت معنی داری بین عملکرد این رقم با سایر موتانت ها وجود نداشت. با در نظر گرفتن عملکرد و درصد کیل، رقم شایان و دو موتانت LM1673 و LM1303 برای کشت در منطقه مطالعه مناسب هستند.

    کلیدواژگان: درصدکیل، تعداد غوزه در بوته، سایه انداز
  • علیرضا کوچکی، علی اشرف جعفری، هوشنگ ناصری راد*، پرویز رضوانی مقدم صفحات 89-116

    به منظور بررسی تاثیر نظام های زراعی و مدیریت بقایای گندم بر عملکرد و اجزاء عملکرد کلزای پاییزه (Brassica napus)، آزمایشی به صورت کرتهای خرد شده نواری در قالب طرح پایه بلوک های کامل تصادفی با سه تکرار در دومکان در سال زراعی 95-94 به اجرا در آمد. فاکتورهای آزمایشی شامل نظام های زراعی در سه سطح کم نهاده، متوسط نهاده و پرنهاده و مدیریت بقایای گندم در چهار سطح صفر، دو، چهار و شش تن در هکتار بود. بر اساس نتایج بالاترین میزان شاخص سطح برگ در مدیریت متوسط و پرنهاده در تیمار دو تن بقایای گیاهی در منطقه چرداول و تیمار چهار تن بقایای گیاهی در منطقه رومشگان بدست آمد. همچنین بیشترین وکمترین میزان تجمع ماده خشک به ترتیب از تیمار چهار تن بقایای گیاهی در مدیریت پر نهاده و تیمار شش تن بقایای گیاهی در مدیریت کم نهاده در هر دو منطقه بدست آمد. اثر نظام های زراعی بر عملکرد بیولوژیک، عملکرد دانه و عملکرد روغن معنی دار شد. بطور کلی مدیریت متوسط و پر نهاده باعث افزایش عملکرد بیولوژیک و عملکرد دانه شد. اثر متقابل نظام های مختلف کشت و سطوح مختلف بقایای گندم بر عملکرد دانه نشان داد که در شرایط مدیریت کم نهاده با افزودن هر یک از سطوح بقایای گندم به خاک عملکرد دانه کلزا کاهش یافت، درحالی که در نظامهای متوسط و پرنهاده افزودن دو و چهار تن بقایای گیاهی تاثیر مثبتی بر خصوصیات رشدی و عملکرد کلزا نشان داد.

    کلیدواژگان: کلزا، نظام های زراعی، مدیریت بقایای گیاهی، شاخص های رشد و عملکرد و اجزاء عملکرد دانه
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  • Mohammad Reza Abbasi *, Abdonaser Mahdipour, S. Alireza Beheshti, Hamid Reza Sharifi Pages 1-17

    IEvaluation of cold-tolerance in genetic resources of some annual forage crops under cold climatic conditions Introduction Temperature influences plant physiological processes, cellular structure and development. Habitat from which plants originate has undeniable effects on plant tolerance to cold temperatures. Plants from higher latitudes exhibit more tolerance to cold stress than plants from lower latitudes. When plants are exposed to cold stress, a sequence of events is triggered inside them, leading to an improved tolerance to the environmental condition. This phenomenon is known as plant hardening. Having access to winter-hardened species and cultivars is one of the important necessities for the development of crop production systems in local microclimates of cold regions. Utilizing genetic diversity in crop plant resources is an important approach towards achieving sustainable agriculture. Diversity in Iran`s forage germplasm for traits such as early maturity, high ratio of leaf to stem, dense ground cover and high yield has been shown in temperate regions such as Karaj and Mashhad (Abbasi, 2009, Abbasi et al., 2017). Testing a selection of these germplasm accessions can determine their potential for growing under water-limited conditions in cold regions. Hence, different genera and species of legumes in national plant gene bank of Iran originated from high latitudes were used to be evaluated under cold growing conditions. Materials and Methods A total of 124 annual-forage accessions from 40 species and 10 genera were selected based on the previous research works and were planted in an experimental filed at Jolge-Rokh agricultural research station. The number of accessions in each genus included Trifolium (36 accessions), annual medics (28 accessions), Onobrychis (9 accessions), Vicia (21 accessions), Melilotus (17 accessions), Lolium (6 accessions), Bromus (5 accessions), and Phalaris (1 accession), Lathyrus (1 accession) and barley (1 accession). Each accession was planted in two 2-meter long rows spaced 50 cm apart using an augmented experimental design. Some of the traits characterized in this study from autumn to spring included growth rate in spring and autumn, cold-tolerance score, plant height etc (IPIGRI, 1984). Statistical descriptive parameters were determined for the evaluated traits. One-way ANOVA (analysis of variance) and Duncan's multiple tests were performed on data of each trait. The analyses were carried out by SPSS 15. Results and Discussion Meteorological data showed that there were a total of 68 days of freezing temperatures in the region from November till March. The lowest absolute temperature recorded was - 17.4 °C in December. Also, the mean of daily minimum temperature for December, January, February and March was below zero and the mean of daily maximum temperature for December, January and February was -10 °C, indicating the occurrence of cold stress in the region. The results of one-way ANOVA analysis for the investigated genera and species showed that there were significant differences among their traits at 1 % probability level, particularly prior to cold stress. Lolium and Bromus were the most tolerant species among the narrow-leaved forages and the tested germplasm. Among forage legumes, sweet clover exhibited the highest tolerance to cold temperatures. Although the species vicia, Lathyrus and Iranian clover were not tolerant to cold, they were found to be beneficial in terms of soil conservation and sustainability due to the production of proper vegetative cover prior to the cold spell, which lasted till the spring of the next year. Based on the results of this investigation, the studied species and genera can be classified into the following groups: 1- Cold-tolerant forage grasses including accessions of Lolium: 14TN00072, 14TN00038, 14TN00052, 14TN00054 and accessions of Bromus: 10TN00049, 10TN00012, 10TN00036, 10TN00039, and 10TN00026. 2- Cold-susceptible forage grasses such as accessions: KC126013 (L. temelentum) and barley. Although this group was sensitive to cold, they produced good vegetative cover on ground before the occurrence of cold, which can be used as mulch for soil protection throughout the year. 3- Cold-tolerant legumes, such as accessions of Melilotus: 58TN00025, 58TN00047, MahNo313, 58TN00182, 58TN00223, 58TN00140, 58TN00181, 58TN00080, and 58TN00190 4- Cold-susceptible forage legumes: they were categorized into two groups, one group produced good vegetative cover on ground before the cold spell such as accessions 44TN00047, 44TN00041, and 44TN00005, and the other group failed to produce enough vegetative cover on ground such as some accessions of annual medics, Onobrychis, and Trifolium.

    Keywords: Cold stress, forage legumes, forage grasses
  • SEYED MOHAMMAD ALI MOFIDIAN *, JAFAR AHMADI, ALI MOGHADDAM Pages 18-39
    Introduction

    Water scarcity is one of the major limiting factors to agricultural production across the globe and it is predicted that drought spells will occur more frequently in the future due to the long-term effects of global warming (Rivero et al., 2007). This has led to a decrease in canopy size, loss in photosynthesis and consequently reduced crop yields. Alfalfa, being perennial and multi cut, as well as having an efficient root system, can tolerate water limited conditions by dormancy and is able to restart its biological activities after irrigating (Mc Williams, 2002). The mechanisms of response to water stress are complex and include activation of growth regulators in molecular and physiological levels. In addition, the yield potential and stability of some Iranian alfalfa ecotypes in different locations have been investigated previously (Mofidian & Moghaddam, 2013).

    Material and Methods

    The experiment was carried out with 10 warm and cold region alfalfa ecotypes in two distinct environments at Seed and Plant Improvement Institute (SPII), Karaj, Iran, over the years 2016-2018. The environments included full irrigation and no watering for 20 days from 22th of June. To conduct a preliminary evaluation of the ecotypes response to water stress, stress susceptibility index (SSI) based on fresh forage yield was calculated. The most important physiological traits measured in this study were as follows: relative water content (RWC), chlorophyll content index (CCI), canopy temperature depression (CTD), and stomatal resistance (SR), Chlorophyll a and b contents and carotenoids. Combined analysis of variance and mean comparisons were done by SPSS Ver.22 and Excel 2016.

    Results and Discussion

    The effect of no watering stress on all of the physiological traits was significant (P<0.01). The ecotypes showed a significant difference in dry matter yield and all physiological measurements except for electrolyte leakage and chlorophyll b content. The year effect indicated a significant difference for chlorophyll b (P<0.05); carotenoids and dry matter yield (P<0.01) but it was not found to be significant for the rest of traits. Among the interactions, environment × year interaction showed no significant effect for all the studied traits. Although, ecotype × environment interaction was significant just for carotenoids (P<0.01), ecotype × year interaction was significant for Dry matter yield, RWC, CTD and SR (P<0.01); and CCI, chlorophyll a (P<0.05), as well. Under full irrigation regime and cut-off irrigation treatment, RWC was respectively 66.26 and 44.06 percent, which indicated that water stress decrease RWC by 32 percent. Electrolyte leakage averaged 26.51 percent under the stress environment, exhibiting a 72 percent decrease in cell membrane stability relative to full irrigation scenario. The chlorophyll content index in non-stress condition was 38 percent greater than that of under stress condition. The canopy temperature depression decreased by 43 percent during water stress imposition. No water shortage treatment led to the least stomatal resistance of 22.22 s/cm; however, this value was 37.87 s/cm under water-limited conditions, which showed a difference of 70 percent.

    Conclusion

    The minimum stress susceptibility index at the first and second year, 0.35 and 0.51, were observed in BAGHDADI and BAMI ecotype respectively, which, among the investigated alfalfa ecotypes, were found to be the most resistance to no watering for 20 days. Overall, KFA6 ecotype showed the minimum electrolyte leakage (13.79 s/cm) and stomatal resistance (23.69 s/cm), respectively. Moreover, KFA6 ecotype had the maximum photosynthetic pigments of 1.623 mg in fresh leaf (gr) that led to the production of 17.48 t/ha dry matter yield and superiority of 14 percent as compared to the two-year mean of all ecotypes under full irrigation and no watering conditions. Keywords: Canopy temperature, stomatal resistance, cell membrane stability, photosynthetic pigments, and alfalfa. References: Mc Williams, D. 2002. Drought strategies for alfalfa. Extension handbook, Department of Extension Plant Sciences, New Mexico State University, Las Cruces, New Mexico. P-1-5. Rivero, R.M., Kojima, M., Gepstein, A., Sakakibara, H., Mittler, R., Gepstein, S., and Blumwald, E.2007. Delayed leaf senescence induces extreme drought tolerance in a flowering plant. Proceeding of National Academic Science, USA 104:19631–19636. Mofidian, S.M.A., and Moghaddam, A. 2013. Analysis of ecotype location interaction in cold-region alfalfa ecotypes. Iranian Journal of Crop Sciences, 15(2): 71-85.

    Keywords: Canopy temperature, stomatal resistance, cell membrane stability, photosynthetic pigments, and alfalfa
  • Babak paykarestan, Soraya Karami *, Tayebeh Basaki Pages 40-53
    Introduction

    Sweet corn (Zea mays L. var. Saccharata) is one of the important and strategic crops, not only due to the short growing season for summer planting (Ti-da et al., 2006; MokhtarPour et al. 2008), but also, for the accumulation of higher quantities of sugars and the soluble polysaccharides in the grain of the endosperm, which can be consumed as a freshly, canned or frozen food. However, the occurrence of drought stress during vegetative and reproductive growth stages is one of the most important challenges to the summer planting of crops such as sweet corn (Ahmadi et al., 2013). Therefore, due to the limited water resources in agriculture, adopting any strategy to conserve water is very important. One of these strategies is irrigation cut-off. Therefore, the aim of the present study was i) to evaluate irrigation cut-off effects on growth indices and conservable grain yield; ii) to identify sweet corn varieties that could be tolerant to irrigation cut-off with slight loss in grain yield under Markazi Province climatic conditions.

    Materials and Methods

    In order to study the effects of irrigation cut-off stress on growth indices (leaf area index: LAI; relative growth rate: RGR; crop growth rate: CGR; net assimilation rate: NAR) and conservable grain yield of three sweet corn varieties (Merit, Chase, KSC.403) and two super sweet corn varieties (Obsession, Basin), a split-plot experiment was conducted in a randomized complete block design with three replications at Millajerd research farm of Payame Noor university of Markazi province in 2016. There were three levels of irrigation regimes assigned to the main-plots; (S0: no irrigation cut-off, S1: irrigation cut-off at the 8- leaf stage and S2: irrigation cut-off at the grain filling stage) and six corn varieties assigned to the sub-plots, respectively. All data were subjected to analysis of variance (ANOVA) using the GLM procedure of SAS statistical program. Also, significant differences among the means were measured using the least significant difference (LSD) test by pairwise comparisons (P < 0.05).

    Results and Discussion

    The results showed that the differences among irrigation patterns and varieties were significant in terms of the measured traits (P<0.01). In addition, the interaction effect of irrigation × varieties was significant for all of the measured traits. The results of present study showed that irrigation cut-off stress had a negative effect on growth indices and conserable grain yield; however, irrigation cut-off at the 8-leaf stage had more negative effects on the varieties and traits as compared to the grain filling stage. Based on the results, the greatest variation observed among irrigation patterns was related to LAI, RGR and conservable grain yield traits, which were affected in the descending order of the irrigation patterns (S0>S2>S1) (P<0.05). Also, the conservable grain yield as the most important economic trait, under the irrigation cut-off stress at the 8- leaf stage and grain filling stage, showed a decrease of 20.87 % (7136.18 kg.ha-1) and 7.96 % (8300.25 kg.ha-1), respectively, as compared to full irrigation (S0) (9018.42 kg.ha-1) (P<0.01). On the other hand, varieties of "Obsession" and "Basin" exhibited higher growth indicies and the least yield loss as compared with the other varieties under irrigation cut-off treatments (S2, S1) and S0 (P<0.05).

    Conclusion

    Our findings indicated that the growth indices including LAI and RGR might be suitable for the identification and selection of sweet varieties that are tolerant to irrigation cut-off. In addition, due to the limited water resources in agriculture, using irrigation cut-off pattern at grain filling stage with non-significant loss of grain yield in sweet corn varieties, especially "Obsession" and "Basin" varieties can be recommended to the farmers in the Markazi province.

    Keywords: Drought stress, Grain filling, 8-leaf Stage, Sweet Corn
  • Sahar Kolahkaj, mahroo Mojtabaie Zamani * Pages 54-74
    Introduction

    Rapeseed cultivation as an important oil seed crop for edible oil supply in Iran and therefore, the identification of cultivars adapted to the particular environmental condition of each region have a particular importance in terms of attaining higher yield in the current state of the country (Hasan et al., 2014). On the other hand, recognizing the relationships between agronomic traits and determining the contribution of each of these traits to yield production provides the necessary information for the breeders to select the most suitable genotype for each region (Basalma, 2008; Marjanovic-Jeromela et al., 2008). Therefore, the purpose of this study was to determine the contribution of effective traits to grain yield and identify the most effective traits as criteria for selecting high yielding cultivars in Ramhormoz region.

    Materials and Methods

    This research was carried out in a randomized complete block design with three replications and ten spring rapeseed genotypes in the cropping year of 2016-2017 in Ramhormoz. The quantitative traits in this study included the number of flowers on the main raceme, siliques on the main raceme, ratio of siliques produced per flowers produced, number of lateral branches, siliques on the lateral branches, grain per silique, 1000-grain weight, silique length, plant height and height of the lowest silique from the soil surface, grain yield, biological yield, number of days to flowering and days to end of flowering, number of days to silique formation and days to maturity, duration of flowering and duration of silique formation to maturity.

    Results and Discussion

    The studied rapeseed genotypes showed a significant difference in the all investigated traits except for success ratio for flower development into silique (%). The Safi6 with the highest number of siliques per plant, Hyola420 with the relatively high number of grain per silique and the highest grain weight and SAN34 with the highest number of grain per silique produced the highest grain yield. These three genotypes also had longer flowering duration. Despite the high number of siliques per plant, the late maturity genotype of Hyola60 with the lowest number of grain per silique and the relatively low grain weight had the least grain yield, due to its grain-filling coinciding with the end of the growing season and heat stress. Among the studied traits, the number of grains per silique had the most positive and significant correlation with grain yield and in stepwise regression analysis, it was the first trait which was entered to the model and explained 71% of the variation of yield along with the number of siliques on the lateral branches, 1000-grain weight and the height of the lowest siliques from the soil surface. According to the results of path analysis, the number of grain per silique had the most positive direct effect on grain yield. The indirect effects of this trait via the number of siliques on the lateral branches, 1000-grain weight and height of the lowest silique from the soil surface were negligible. In spite of the relatively high direct effect of the number of siliques in the lateral branches on grain yield, there was no significant correlation between the number of siliques on the lateral branches and grain yield, due to the negative indirect effect via 1000-grain weight and height of the lowest silique from the soil surface

    Conclusion

    The results of this study showed that Safi6, Hyola420 and SAN34 were the most suitable genotypes to achieve the highest yield in Ramhormoz region (with consideration of the recommended planting date). Grain number per siliques with the highest positive direct effect on grain yield and negligible indirect effects via other traits was introduced as criteria for selection of high yielding genotypes in spring rapeseed breeding programs.

    Keywords: Correlation, genetic diversity, path analysis, stepwise regression
  • Majid Jafaraghaei*, Amir hooshang Jalali Pages 75-88
    Introduction

    Cotton (Gossypium hirsutum L.) is an indeterminate plant that growth and harvesting of multistage fibers along with the seed is possible in one crop season. Cotton, however, is a salt tolerant plant, but salinity, especially in dry and semi-arid regions of the world, can lead to a loss of production of this plant. Reduction of cotton yield due to use of saline irrigation water in surface irrigation methods was reported at 0, 10, 25 and 50% in salinity levels of 5.1, 6.4 and 8.4 and 12 dS m-1 respectively. Salinity stress can affect the growth of germination and plant growth, and reduce the amount of photosynthetic active radiation absorbed by the plant and consequently photosynthesis and yield. The purpose of this study was to evaluate the effect of irrigation water salinity on vegetative growth and yield of two cultivars and six cotton mutants produced in the nuclear power research institute.

    Materials and Methods

    This research was carried out in 2013 using split plot experiment in randomized complete block design with four replications at Rudasht salinity and drainage research station in Isfahan. Irrigation water treatments at three levels (4, 8 and 12 dS m-1) consisted of main plots and two varieties of Varamin and Shayan along with six mutants of cotton were sub plots. Saline water is supplied from drainage water with a salinity of 25 dS m-1 from the Rodasht saline research station, which was mixed at the site of the project with river water (maximum 2 dS m-1) in the place of special reservoirs and transferred to the sweets after delivery. It has been transmitted to the experimental plots by pipelines. The measured traits during the study were: the amount of light received in the middle and the bottom of the plant's canopy using a light meter at 7 am and 13 pm, the number of bolls per plant, lint percentage (fiber weight to seed weight ratio), harvest index and yield. All statistical analysis was performed using SAS software and means were compared by Duncan's multiple range test.

    Results and Discussion

    The effect of salinity treatments on number of bolls per plant and yield was significant at 5% level, but the effect of salinity interaction and genotype on yield and yield components were not statistically significant. Based on the results obtained in the morning, the amount of light received in the floor of canopy in treatments of 12, 8 and 4 dS m-1 were 329, 317 and 303 foot candle and at noon were 358, 348 and 310 foot candle, respectively. Shayan cultivar with the yield of 2852 kg ha-1 had the highest yield, but there was no significant difference between the yield of this cultivar and the other mutants used. One of the negative effects of salinity stress is the reduction of plant leaf area due to the reduction of plant cell pressure potential and the result of this process is the reduction of absorption of active photosynthesis radiation. In this case, the amount of light received to the canopy cover of the plant increases. Therefore, measurements of light in the floor of canopy can be considered as a measure of vegetation growth. In general, Varamin varieties and mutants such as LM1676 and LM1321 are among the genotypes with higher foliage than the other genotypes with less light in the center and floor of canopy. Therefore, less light in the floor of canopy (more foliage) does not necessarily mean more economic yield. The number of bolls per plant in salinity treatments of 4, 8 and 12 dS m-1 was 6.92, 6.75 and 4.49, respectively.

    Conclusions

    According to the results, most cotton mutants used in this study have good potential and can be considered as promising mutants to introduce new cultivars, especially in cases where available water sources are not of appropriate quality. Given that these mutants are produced by gamma rays, it seems that the use of this method can be considered as an appropriate approach in expediting the introduction of new cultivars of cottons. Key words: Bolls per plant, Canopy, Lint percent

    Keywords: Bolls per plant, Canopy, Lint percent
  • Alireza Koochaki, Ali Ashraf Jafari, Houshang Naseri rad*, Parviz Rezvani Moghadam Pages 89-116

    Common tillage practices are known to accelerate soil erosion and reduce the carbon and organic contents of soils, leading to the destruction of the soil structure. Nowadays, soil erosion is considered to be a major challenge to agricultural production. Maintaining adequate quantities of crop residues in the soils is an effective way to overcome the decline in soil quality (Kazemi & Zakeri, 2006). Research conducted in different canola producing regions of the world indicates that the effect of various tillage systems on seedbed preparation for canola has been different, depending on soil type and climate condition. So that some studies recommend the direct seeding using minimum tillage and the others recommend deep soil plowing by moldboard for increasing canola yield.(Reshad Sadeghi et al., 2006). This research was aimed to investigate the effects of different farming systems and wheat residue management on yield and yield components in autumn canola.Materials and MethodsA strip plot design was adopted in a randomized complete block layout with three replications in 2015 and 2016 cropping seasons in two locations (Sarableh, and Roumeshgan) in the southern west of Iran. The first experimental factor consisted of three farming systems: low input (one-time disk plowing + 25% of the crop nutrient requirement as chemical fertilizer + two times weed manual control), medium input (one-time moldboard plowing, one-time disk plowing 50% of the crop nutrient requirement as chemical fertilizer+ once weed manual control+ one-time weed control by herbicide) and high input (two times moldboard plowing +two times disk plowing + 100% of the cop nutrient requirement as chemical fertilizer+ two times weed control by herbicide). The second experimental factor was wheat residues management at four levels of 0 as control, 2, 4 and 6 tons/h. The first and second factors were considered as vertical and horizontal factors.Result and Discussion The results showed that the highest leaf area indices were obtained with high input farming system under 2 and 4 t/ha of wheat residues in Sarableh and Roumeshgan,regions, respectively. The highest and lowest accumulation of dry matters were obtained in high input farming system under 4 t/ha of wheat residues and, low input farming system under 6 t/h of wheat residues at both locations, respectively. The interaction effect of farming systems and wheat residues was significant on number of silique per plant and grain yield. This results showed that in low-input management conditions, by adding each level of wheat residue to soil, seed yield decreased, while in medium and inward systems, adding two and Four tons of plant remains showed a positive effect on the growth characteristics and yield of rapeseed. The results showed that the application of wheat residues due to its high carbon content may increase the soil microbial activity and in such condition, nitrogen stored in microorganisms bodies and then is absorbed by plant, especially in the early stages where plant is faced with nitrogen deficiency (Turmel et al., 2015). Autumn plants, including canola, in the absence of nitrogen, cannot complete rosette growth in the early stages of growth, and hence they will be less developed during the growing season. Therefore, in low-input systems, application of high levels of wheat residues resulted in the reduced biological and grain yield in canola as a result of nitrogen organification.

    Keywords: Canola, farming systems, management of plant residue, growth indices, grain yield, yield components