جداسازی و غربالگری جدایه های ازتوباکتر بومی خاک های شور و سنجش صفات محرک رشدی آن ها

نوع مقاله: مقاله پژوهشی

نویسندگان

1 دانشجو/دانشگاه علوم کشاورزی ومنابع طبیعی گرگان

2 استادیار علوم خاک گرگان

3 هیات علمی گروه خاک دانشگاه کشاورزی و منابع طبیعی گرگان

4 دانشیار علوم خاک گرگان

چکیده

شوری یکی از مهم­ترین تنش­های غیرزیستی بوده که قابلیت تولید گیاه را تحت تأثیر قرار می­دهد. با توجه به روند افزایش توسعه اراضی شور و کمبود اراضی مطلوب برای کشاورزی، شناسایی راهکارهایی برای افزایش مقاومت گیاهان در برابر شرایط شوری ، اهمیت زیادی دارد. استفاده از باکتری­های محرّک رشد از جمله ازتوباکترها یکی از راهکارهای  مهم تعدیل اثرات شوری محسوب می­شود. در این راستا و برای انجام پژوهش حاضر، 15 نمونه از خاک­های شور اراضی استان گلستان به‌منظور جداسازی باکتری ازتوباکتر جمع­آوری شد. تعداد 32 جدایه باکتریایی جداسازی و خالص­سازی شد. بعد از انجام آزمایشات فیزیولوژیک و بیوشیمیایی تعداد 23 جدایه منسوب به ازتوباکتر انتخاب شد. جدایه­ها از نظر توانایی رشد در غلظت­های 2، 5 و 10 درصد نمک، توانایی تولید اگزو­پلی­ساکارید، توانایی تحمل به خشکی، برخی ویژگی­های محرّک رشدی گیاه شامل توان تثبیت نیتروژن مولکولی، انحلال پتاسیم معدنی نامحلول، انحلال فسفات­ معدنی نامحلول، تولید ایندول­استیک­اسید (IAA) و تولید هیدروژن­سیانید مورد ارزیابی قرار گرفتند.  نتایج پژوهش نشان داد که با افزایش میزان نمک رشد جدایه­ها کاهش یافت. توانایی تولید اگزوپلی‌ساکارید (4/0 تا 6/5 گرم بر لیتر) در 2/78 درصد از جدایه­ها مشاهده شد. افزایش سطح پلی­اتیلن­گلیکول باعث کاهش میزان رشد جدایه­ها شد .نتایج حاصل از آزمون­های محرّک رشد گیاه نشان داد که توان حل­کنندگی فسفات جدایه­ها (5/52 تا 1/218 میلی­گرم بر لیتر)، توان تولید ایندول استیک اسید (4/2 تا 2/60 میلی­گرم بر لیتر)، توان حل­کنندگی ­پتاسیم جدایه­ها ( 9/12 تا 3/28 میلی­گرم بر لیتر)، توان تثبیت زیستی نیتروژن ( 9/2 تا 1/5 نانومول اتیلن بر ساعت) بود. از بین 23 جدایه منسوب به ازتوباکتر بر اساس آزمون­های فیزیولوژیک باکتری در سطوح مختلف نمک و خشکی و آزمون­های محرّک رشدی، جدایه AZ13 به‎عنوان جدایه برتر انتخاب شد.

کلیدواژه‌ها


عنوان مقاله [English]

Isolation and screening of native azotobacter from salt affected soils and measurement of their growth promoting properties

نویسندگان [English]

  • Reza Khodadadi 1
  • Reza Ghorbani-Nasrabadi 2
  • mohsen olamaee 3
  • Seyed Alireza movahedi Naeini 4
1 gorgan university
2 PhD of Soil Biology & Biotechnology Dept. of Soil Science College of Soil & Water. University College of Agriculture. Gorgan University of Agricultural Sciences and Natural Resources,Gorgan, Iran
3 Ph.D) Associate Professor Dept. of Soil Science, Faculty of Water and soil Gorgan University ,Iran
4 Ph.D) Associate Professor Dept. of Soil Science, Faculty of Water and soil Gorgan University ,Iran
چکیده [English]

Salinity as one of the major abiotic stresses severely affects crop productivity. Plant growth promoting bacteria is being considered to ameliorate salinity stress. Fifteen samples of salt affected soils from Golestan province were collected to isolate Azotobacter. Thirty- two bacterial isolates were isolated and purified. Physiological and biochemical tests confirmed twenty-three isolates belongs to Genus Azotobacter. The isolates were assessed for their growth in liquid medium supplemented with 2, 5 and 10 % of salt. Exopolysaccharide production, drought stress tolerant and some selected growth promoting properties such as nitrogen fixation, solubilization insoluble potassium, tri-calcium phosphate solubilization, indole acetic acid and hydrogen cyanid production capability was evaluated. Results showed that increasing salt concentration had negative effect on bacterial growth. Exopolysaccharide production (0.4-5.6 g L-1) was positive by 78.2% of the isolates. Higher levels of polyethylene glycol reduced growth of the isolates. Plant growth promoting tests showed tri-calcium phosphate solubilization (52.5-218.1 gL-1), IAA production (2.4 - 60.2 mg L-1), potassium solubilization (12.9-28.3 mg L-1) and biological nitrogen fixation (2.9 - 5.1 nmol ethylene hr-1). Among the 23 isolates to Azotobacter, based on physiological tests of bacteria in different levels of salt and drought and PGPR tests, isolate AZ13 was selected as the superior isolate.

کلیدواژه‌ها [English]

  • "
  • salinity"
  • polysaccharide"
  • drought stress"
  • phosphate solubilization
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