تعیین مشخصات باکتری‌های ریزوبیا جدا شده از خاک‌های آلوده به آرسنیک در مناطق جنوب شرقی استان کردستان و تأثیر آنها بر روی رشد گیاه

نویسندگان

1 دانشجوی سابق کارشناسی ارشد دانشگاه کردستان

2 دانشیار دانشگاه کردستان

چکیده

باکتری­های همزیست با ریشه بقولات از ریشه گیاهان یونجه (Medicago sativa L.)، نخود (Cicer arietinum L.) و یونجه زرد (Melilotus officinalis L.) رشد کرده در خاک­های آلوده به آرسنیک در جنوب شرقی استان کردستان جداسازی گردید. جدایه­ها براساس خصوصیات فیزیولوژیکی و بیوشیمیایی متعلق به جنس Rhizobium و Ensifer تشخیص داده شد. وجود سیستم مقاومتی به آرسنیک، سیستم ars، با استفاده از آغازگرهای اختصاصی ژن arsC بررسی و به اثبات رسید. نرخ رشد جدایه­ها در محیط کشت YEMB به اضافه غلظت­های 400 – 100 میلی مولار آرسنات بررسی گردید. سویه­های جدا شده از یونجه (AB1، AB3)، نخود (PA2، PC2) و یونجه زرد (YA1) توانائی تحمل 350 میلی مولار آرسنات را داشتند. همچنین سویه­های AB1، PA2 و YA1 توانائی تحمل غلظت 400 میلی مولار آرسنات را داشتند. به منظور بررسی تأثیر آلودگی به آرسنیک بر روی رابطه همزیستی یونجه و نخود با باکتری­های ریزوبیا و میزان رشد گیاهان، آزمونی در قالب بلوک­های کاملاً تصادفی در سه تکرار و در پنج غلظت آرسنیک (100، 75، 50، 10 و صفر میلیگرم بر کیلوگرم خاک) و با تلقیح یا بدون تلقیح دو سویه باکتری، AB1 و PA2 انجام گردید. وزن خشک و وزن تر ریشه و اندام­های هوائی یونجه و نخود با افزایش غلظت آرسنیک در خاک کاهش یافت. نتایج نشان داد که وزن خشک و وزن تر ریشه و اندام­های هوائی هر دو گیاه در بوته­های تیمار شده توسط سویه­های باکتری بصورت معناداری بالاتر از فاکتورهای مشابه در گیاهان تلقیح نشده با باکتری بود. براساس نتایج بدست آمده سویه­های AB1 و PA2 با توانائی مقاومت به غلظت­های بالای آرسنیک به همراه گیاهان همزیست می­توانند جهت پالایش خاک­های آلوده به آرسنیک مورد استفاده قرار گیرند. 

کلیدواژه‌ها


عنوان مقاله [English]

Characterization of rhizobial bacteria isolated from arsenic-contaminated site in south-eastern Kurdistan province and their influence on plant growth

نویسندگان [English]

  • R. Saadati 1
  • B. Bahramnejad 2
  • B. Harighi 2
1 Former MSc. Student of University of Kurdistan
2 Associate professor, University of Kurdistan
چکیده [English]

Symbiotic bacteria associated with the root of legume plants were isolated from soil and the root nodules of alfalfa (Medicago sativaL.), chickpea (Cicer arietinum L.) and yellows alfalfa (Melilotus officinalis L.) grown in arsenic-contaminated areas in south eastern part of Kurdistan province, Iran. According to physiological and biochemical  properties, isolates were identified as the members of Rhizobium and Ensifer genus. The presence of arsenic resistant system known as ars system was confirmed by amplification using primers corresponding to arsC gene. Growth rate of strains in different concentrations of arsenate was investigated in YEMB medium supplemented with 100-400 mM arsenate. Alfalfa,s isolates (AB1, AB3), chickpea,s isolates (PA2, PC2), yellow alfalfa,s isolate (YA1) and standard strain (Sinorhizobium meliloti SM117) were tolerant to 350 mM arsenate and (AB1, PA2 and YA1) isolates were moderately capable to grow at 400 mM arsenate. Among the identified strains, AB1 and PA2, were selected for greenhouse experiments. In order to evaluate the effect of arsenic contamination on legume-rhizobia symbiosis and biomass production of alfalfa and chickpea plants, an experiment was carried out based on a completely randomized design with a factorial arrangement in three replications. Experiment factors consisted of, three levels of rhizobia inoculation (with and without inoculation of AB1 and PA2) and five levels of arsenic concentrations (0. 10, 50, 75 and 100 mgkg-1 soil) under greenhouse conditions for 8 weeks. Results obtained in this study indicated that the fresh weight and dry weight of alfalfa and chickpea (shoot and root) were decreased as the arsenic concentration of the soil was increased. The results also showed that fresh and dry shoot and root weight of alfalfa and chickpea were significantly higher in rhizobia-inoculated treatments compared to non-inoculated plants.

کلیدواژه‌ها [English]

  • Arsenic resistance
  • legumes
  • Rhizobia
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