نوع مقاله : مقاله پژوهشی
نویسندگان
1 استادیار، بیولوژی و بیوتکنولوژی خاک، گروه علوم و مهندسی خاک، دانشکده کشاورزی، دانشگاه مراغه
2 دانشجوی سابق کارشناسی ارشد، گروه علوم و مهندسی خاک، دانشکده کشاورزی، دانشگاه مراغه
3 استاد، فیزیولوژی گیاهان زراعی، گروه مهندسی تولید و ژنتیک گیاهی، دانشکده کشاورزی، دانشگاه مراغه
4 دانشیار، پیدایش، رده‌بندی و ارزیابی خاک، گروه علوم و مهندسی خاک، دانشکده کشاورزی، دانشگاه مراغه
چکیده
کلیدواژه‌ها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Background and Objectives: Phosphorus bioavailability in soil is a key issue in plant nutrition, especially in calcareous and acidic soils, where it rapidly forms insoluble compounds. Phosphate-solubilizing bacteria (PSB) have been used as biofertilizers to release available phosphorus from these sources. Barvar 2, a phosphate biofertilizer widely used in the country, contains two strains of phosphate-dissolving bacteria: Pantoea agglomerans P25 and Pseudomonas putida P13. These bacteria release organic acids, which lower soil pH, chelate minerals, and affect ion exchange reactions to mobilize phosphorus. However, the success of these biofertilizers depends on the bacteria’s ability to compete with native soil bacteria and colonize plant roots effectively. This aspect of the biofertilizer’s functionality is a concern and requires further study. One key factor influencing root colonization is the ability of bacteria to form biofilms in the rhizosphere. Biofilms enhance bacterial survival and colonization by providing protection against environmental stressors and improving bacterial persistence in the soil. Studies suggest that bacteria capable of forming biofilms are more efficient at colonizing roots and promoting plant growth. Biofilm formation is a desirable trait for growth-promoting bacteria, and its effectiveness varies across different bacterial strains. These bacteria typically form biofilms that help retain moisture and improve their overall survival compared to planktonic forms. Given the importance of phosphorus for cereal production, especially barley, understanding how biofilm formation by PSB bacteria affects plant growth under different phosphorus treatments in calcareous soils is crucial. This study aims to explore the ability of Barvar 2 bacteria to form biofilms and their impact on barley growth when used as a biofertilizer in varying soil conditions.
Materials and Methods: Barvar 2 biofertilizer package prepred from market. Barley seed var. Ansar was obtained from the Dryland Agricultural Research Institute. Barley seeds were disinfected with bleach and alcohol and grown under completely sterile conditions until the two-leaf stage (Zadoks Stage 12) in a minimum salt solution, for extracting root exudates. The biofilm formation by the bacterial components of the biofertilizer in the root exudates was assessed using the crystal violet staining method. In this experiment, TSB medium at a concentration of 0.5 X was used as the control. The ability to dissolve phosphate from a phosphate rock source was performed using liquid Sperber medium over a period of 7 days. To investigate the correlation between biofilm formation ability and barley growth, a pot experiment was conducted in a factorial within a completely randomized design. The treatments were including with and without biofertilizer bacteria, and using powdered phosphate rock at three levels: zero, 6 and, 12 mg/kg of soil. The research was conducted in greenhouse of the Faculty of Agriculture at University of Maragheh. At the end of the experiment, Yield and yield components, including straw weight, number of grains, plant height, leaf weight, biological yield, harvest index, 1000 seed weight, spike weight, and seed weight, were measured. The data obtained were analyzed using SAS software, and mean comparisons were made at a 5% probability level of Duncan’s test.
Results: Our results showed that biofilm-forming ability of the bacteria separately in the barley root exudate medium was higher than in the TSB medium. However, this effect was not observed when the two bacteria were mixed. The biofilm-forming ability of P. agglomerans was greater than P. putida, and the bacterial mixture affected biofilm formation. Inoculation of the Sperber medium containing phosphate rock with P. putida increased the EC of the medium to (110µS/cm), whereas inoculation with P. agglomerans increased the EC to (528µS/cm), compared to the control. However, inoculation of the Sperber medium containing phosphate rock with P. putida caused a 2.47-unit drop in pH, and a 3.86-unit drop was observed with P. agglomerans, compared to the control. Linear relationships between the traits of grain weight in the pot, thousand-grain weight, and harvest index with the biofilm formation index by the components of the biofertilizer showed a significant correlation with determination coefficients (R²) of 74%, 97%, and 97%, respectively.
Conclusion: This study sheds light on the importance of bacterial biofilm formation in the context of biofertilizers, particularly when the bacteria are involved in nutrient solubilization from sources like phosphate rocks. The significant correlations (R² of 74% for grain weight, 97% for thousand-grain weight, and 97% for harvest index) with the biofilm formation index suggest that biofilm formation by biofertilizer bacteria is closely related to crop yield parameters. This indicates that assessing biofilm formation could serve as an important criterion in evaluating the efficacy of biofertilizers. It also points to the potential for improving crop yield through the strategic use of biofilm-forming bacteria in agricultural systems.
کلیدواژه‌ها [English]
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