Purpose

This study aims to characterize plant growth-promoting rhizobacteria (PGPR) in sunflowers growing in different locations at North West of Iran.

Materials and methods

Sunflower plants were collected from different regions of West Azarbaijan, and rhizospheric bacterial strains were isolated and screened for PGP traits. Identification and characterization of the PGPR were conducted based on 16s rDNA sequences and phenotypic analysis, the strains clustered for genetic diversity by rep-PCR method.

Results

Among the 80 bacterial isolates, 20 showed PGP traits and were selected for other potentials. All the selected isolates produced indole-3-acetic acid at the rate of 9.2–33.7 mg/ml. In addition, 13, 15, 12, and 16 were positive for phosphate solubilization, siderephore, hydrogen cyanide, and ammonia production, respectively. The results from a subsequent pot experiment indicated that PGPRs distinctly increased sun flower shoot and root length, shoot and root fresh weight, as well as shoot and root dry weight. Based on 16S rDNA sequences and biochemical and physiological characteristics, 20 PGPRs were identified as Pseudomonas fluorescens (five isolates), Pseudomonas aeruginosa (four isolates), Pseudomonas geniculata (one isolate), Bacillus subtilis (four isolates), Bacillus pumilus (two isolates), Stenotrophomonas maltophilia (two isolates), and Brevibacterium frigoritolerans (two isolates). In rep-PCR, PGPR isolates were differentiated into seven clusters (A–G) at 65% similarity level. These results demonstrated the existence of a considerable species richness and genetic diversity among PGPRs isolated from different regions of North West of Iran.

Conclusions

To the best of our knowledge, this is first report for the identification and characterization of B. frigoritolerans as PGPR in sunflower plants.

中文翻译：

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从伊朗向日葵 (Helianthus annuus L.) 中分离出的潜在植物促生长根际细菌的表征

目的

本研究旨在表征生长在伊朗西北部不同地点的向日葵中的植物生长促进根际细菌 (PGPR)。

材料和方法

从西阿扎拜疆的不同地区收集向日葵植物，分离根际细菌菌株并筛选 PGP 性状。基于16s rDNA序列和表型分析对PGPR进行鉴定和表征，通过rep-PCR方法对菌株进行遗传多样性聚类。

结果

在 80 株细菌分离株中，20 株表现出 PGP 性状，并被选为具有其他潜力。所有选定的分离株都以 9.2–33.7 mg/ml 的速率产生吲哚-3-乙酸。此外，分别有 13、15、12 和 16 对磷酸盐增溶、铁载体、氰化氢和氨生成呈阳性。随后的盆栽实验结果表明，PGPRs 显着增加了向日葵的芽和根长度、芽和根鲜重，以及芽和根干重。根据16S rDNA序列和生化生理特征，鉴定出20株PGPRs为荧光假单胞菌（5株）、铜绿假单胞菌（4株）、膝状假单胞菌（1株）、枯草芽孢杆菌（四种分离物）、短小芽孢杆菌（两种分离物）、嗜麦芽窄食单胞菌（两种分离物）和冷热短杆菌（两种分离物）。在 rep-PCR 中，PGPR 分离株以 65% 的相似度被分化为七个簇 (A-G)。这些结果表明从伊朗西北部不同地区分离的 PGPR 之间存在相当大的物种丰富度和遗传多样性。

结论

据我们所知，这是对向日葵植物中作为 PGPR的B. frigoritolerans进行鉴定和表征的第一份报告。