جداسازی، غربالگری و شناسایی ریزوباکتری‌های محرک رشد مقاوم به تنش‌های غیرزیستی از میکروبیوم گیاه یونجه (Medicago sativa) در خاک‌های خشک و شور استان کرمان

نوع مقاله : مقاله پژوهشی

نویسندگان

1 گروه علوم و مهندسی خاک، دانشکده کشاورزی، دانشگاه شهید باهنر کرمان، کرمان، ایران.

2 علوم و مهندسی خاک، دانشکده کشاورزی، دانشگاه ولی عصر (عج) رفسنجان، کرمان، ایران.

چکیده

این مطالعه با هدف بررسی خصوصیات ریزوباکتری‌های بومی محرک رشد از قبیل تثبیت بیولوژیکی نیتروژن، انحلال فسفات، تولید سیانید هیدروژن و اگزوپلی ‌ساکارید در راستای تهیه کود زیستی مناسب و کارآمد منطقه انجام شد. در این مطالعه، 135 باکتری از ریشه گیاه یونجه در خاک‌های شور و خشک استان کرمان جداسازی، غربالگری و شناسایی شد و برخی از ویژگی‌های محرک رشد بودن این ریزوباکتری‌ها هم مورد بررسی قرار گرفت. بدین منظور ریزوباکتری‌ها از نظر توانایی تثبیت نیتروژن، انحلال فسفات‌های آلی و معدنی نامحلول در محیط کشت جامد و مایع، تولید سیانید هیدروژن و اگزوپلی ساکارید مورد بررسی قرار گرفتند. رشد ریزوباکتری‌ها در غلظت‌های مختلف کلرید سدیم (0، 1، 3 و 5 درصد) و غلظت‌های مختلف پلی اتیلن گلیکول 6000 (پتانسیل آبی 0، 1-، 2- و 5/3- مگاپاسکال) نیز مورد بررسی قرار گرفت. این بررسی‌ها نشان داد که 72 درصد ریزوباکتری‌ها در سطح 5 درصد نمک کلرید سدیم و 76 درصد در سطح پتانسیل آبی 5/3- مگاپاسکال تقریبا هیچ رشدی نداشتند. از طرفی 50 درصد ریزوباکتری‌ها توانایی تولید سیانید هیدروژن در شرایط شور را داشتند. سه باکتری SM16، SM65 و SM89 از کارآمدترین ریزوباکتری‌های تولیدکننده اگزوپلی ساکارید و دارای قدرت حل کنندگی فسفات بالا به ترتیب به میزان 102، 5/98 و 7/121 میلی‌گرم بر لیتر بودند و از طرفی جزء ریزوباکتری‌های مقاوم به تنش‌های غیرزیستی نیز قرار داشتند. بنابراین این سه سویه‌ باکتریایی ایمن و کارآمد ممکن است پتانسیل خوبی برای تبدیل شدن به یک کود زیستی با کیفیت بالا جهت بهبود رشد محصولات زراعی در منطقه را داشته باشند.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Isolation, screening and identification of growth-promoting rhizobacteria resistant to abiotic stresses from the microbiome of Alfalfa (Medicago sativa) in saline and arid soils in Kerman province

نویسندگان [English]

  • Mahboobeh Abolhasani Zeraatkar 1
  • Ahmad Tajabadi Pour 2
1 Department of Soil Science, Agriculture Faculty, Shahid Bahonar University of Kerman, Kerman, Iran.
2 Department of Soil Science, Faculty of Agriculture, Vali-e-asr University of Rafsanjan, Kerman, Iran.
چکیده [English]

The purpose of this study is to investigate the characteristics of plant growth promoting rhizobacteria that stimulate plant growth, such as biological nitrogen fixation, phosphate solubilization, and produce hydrogen cyanide and exopolysaccharides, to prepare suitable and efficient biofertilizers. In this research, 135 Rhizobacteria strains were isolated, screened and identified from saline and arid soils in Kerman Province, and some of their growth-promoting characteristics were studied. The Rhizobacteria strains were studied with respect to their ability to fix nitrogen, solubilize insoluble organic and inorganic phosphates in solid and liquid culture media, and produce hydrogen cyanide and exopolysaccharides. Their growth at various sodium chloride concentrations (0, 1, 3, and 5%) and at different polyethylene glycol 6000 concentrations (water potential 0, -1, -2, and -3.5 MPa) was also investigated. According to the results, 72% and 76% of the Rhizobacteria strains exhibited almost no growth at 5% sodium chloride concentration and at water potential -3.5 MPa, respectively. In addition, 50% of them were able to produce hydrogen cyanide under saline conditions. Three of the strains (SM16, SM65, and SM89) were the most efficient producers of exopolysaccharides and had high phosphate solubilization ability (102, 98.5 and 121.7 mL/L, respectively) and were also among Rhizobacteria strains resistant to abiotic stresses. Three strain safe and efficient strains can have great potential to be used as a high quality biofertilizer for improving growth of crop plants in the region.

کلیدواژه‌ها [English]

  • Abiotic stress
  • Biofertilizer
  • Exopolysaccharide
  • Hydrogen cyanide
  • Phosphate solubilization

EXTENDED ABSTRACT

Introduction:

Microorganisms are often exposed to environmental stresses such as limited nutrient availability, salinity and sudden changes in osmolarity, drought stress, and temperature rise or fall. Proper responses of bacteria under these conditions are necessary for them to adapt effectively to environmental stresses and changes. Sinorhizobium bacteria inside alfalfa roots can be used for various purposes in agriculture. Some of these bacteria are also among plant growth-promoting Rhizobacteria that stimulate and promote plant growth often via one or more mechanisms, such as biological nitrogen fixation, phosphate solubilization, siderophore and the exopolysaccharide production, and increased availability of nutrients required by plants.  

 

Materials and methods:

In this research, 135 Rhizobacteria strains were isolated, screened and identified from saline and arid soils in Kerman Province, and some of their growth-promoting characteristics were studied. The Rhizobacteria strains were studied with respect to their ability to fix nitrogen, solubilize insoluble organic and inorganic phosphates in solid and liquid culture media, and produce hydrogen cyanide and exopolysaccharides. Their growth at various sodium chloride concentrations (0, 1, 3, and 5%) and at different polyethylene glycol 6000 concentrations (water potential 0, -1, -2, and -3.5 MPa) was also investigated.  

 

Results and discussion:

 According to the results, 72% and 76% of the Rhizobacteria strains exhibited almost no growth at 5% sodium chloride concentration and at water potential -3.5 MPa, respectively. In addition, 50% of them were able to produce hydrogen cyanide under saline conditions. Three of the strains (SM16, SM65, and SM89) were the most efficient producers of exopolysaccharides (364, 318.7 and 198.3 µg/mL, respectively) at 3% sodium chloride stress level, had high phosphate solubilization ability (102, 98,5 and 121.7 mL/L, respectively) and were also among Rhizobacteria strains resistant to abiotic stresses.  

 

Conclusions:

The viability and effectiveness of native Sinorhizobium bacteria are reduced due to salt and osmotic stress, water scarcity, high soil temperature, and soil acidity and alkalinity. Sinorhizobium strains differ in their tolerance to environmental factors. Inoculation of alfalfa with native strains of Sinorhizobium adapted to specific environments and resistant to abiotic stresses, on the one hand, can increase nodulation and nitrogen fixation under stress conditions, on the other hand, to improve plant growth and yield through their potential to stimulate plant growth. Inoculating alfalfa with effective strains of Sinorhizobium has significant economic and environmental benefits. The main purpose of this study was to select native Sinorhizobium strains isolated from saline and dry regions in Kerman Province that were tolerant to unfavorable environmental conditions and were also able to stimulate plant growth. These safe and efficient strains can have great potential to be used as a high quality biofertilizer for improving growth of crop plants in the region.

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