Rhizobacteria containing 1-aminocyclopropane-1-carboxylic acid-deaminase (ACC-deaminase) and exopolysaccharides (EPS) activity are important to induce stress tolerance in plants. The present study was conducted to screen and characterize plant growth promoting rhizobacteria (PGPR) with ACC-deaminase and EPS-producing activity for improving maize growth under drought stress. Eighty-five rhizobacterial strains were isolated from the rain-fed areas, among those sixty-nine isolates were able to utilize ACC and thirty-one strains were found positive for EPS production. These strains containing ACC-deaminase and/or EPS-producing activity were subjected to drought tolerance assay by inducing water stress in media using polyethylene glycol (PEG) 6000. Based on results of the drought tolerance bioassay, twelve most prominent strains were selected to evaluate their growth promoting abilities in maize under water stressed conditions by conducting jar trial. The impact of strains on maize growth parameters was variable. Strains with co-existence of ACC-deaminase and EPS-producing activity showed comparatively better results than those with either ACC-deaminase or EPS-producing activity only. These strains were also significantly better in improving the plant physiological parameters including photosynthesis rate, stomatal conductance, vapor pressure, water use efficiency, and transpiration rate. The strain D3 with co-existence of ACC-deaminase and EPS-producing activity was significantly better in colonizing maize roots, improving plant growth, and physiological parameters. The strain was named as Bacillus velezensis strain D3 (Accession number MT367633) as confirmed through results of 16S rRNA partial gene sequencing. It is concluded that the strains with co-existence of ACC-deaminase and EPS-producing activity could be better suited for improving crop growth and physiology under drought stress. This article is protected by copyright. All rights reserved.

中文翻译：

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评估具有 ACC 脱氨酶活性的产 EPS 根际细菌在干旱胁迫下改善玉米生长和生理的潜力

含有 1-氨基环丙烷-1-羧酸脱氨酶（ACC-脱氨酶）和胞外多糖（EPS）活性的根际细菌对于诱导植物的胁迫耐受性很重要。本研究旨在筛选和表征具有 ACC 脱氨酶和 EPS 产生活性的植物生长促进根际细菌 (PGPR)，以改善干旱胁迫下的玉米生长。从雨养区分离出 85 株根际细菌菌株，其中 69 株能够利用 ACC，发现 31 株对 EPS 生产呈阳性。通过使用聚乙二醇 (PEG) 6000 在培养基中诱导水分胁迫，对这些含有 ACC 脱氨酶和/或 EPS 生产活性的菌株进行耐旱试验。 基于耐旱生物试验的结果，选择了十二个最突出的菌株，通过进行罐试验来评估它们在水分胁迫条件下在玉米中的生长促进能力。菌株对玉米生长参数的影响是可变的。与仅具有 ACC 脱氨酶或 EPS 产生活性的菌株相比，ACC 脱氨酶和 EPS 产生活性共存的菌株显示出相对更好的结果。这些菌株在改善植物生理参数方面也明显更好，包括光合作用速率、气孔导度、蒸汽压、水分利用效率和蒸腾速率。ACC-脱氨酶和EPS产生活性共存的菌株D3在定殖玉米根、改善植物生长和生理参数方面明显更好。经16S rRNA部分基因测序结果证实，该菌株命名为Bacillus velezensis D3菌株（登录号MT367633）。结论是具有ACC-脱氨酶和EPS产生活性共存的菌株可能更适合在干旱胁迫下改善作物生长和生理。本文受版权保护。版权所有。