Plant growth-promoting rhizobacteria (PGPR) have important roles in improving plant growth and alleviating stress induced damage under drought stress conditions. The aims of this study are: 1) to isolate and identify drought-tolerant PGPR from rhizosphere soil of jujube, a drought-tolerant plant grown in semi-arid and arid regions; and 2) to evaluate the effects of inoculation with the isolated strains on the growth and physiological responses of jujube seedlings under drought stress conditions. Rhizosphere bacteria with 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity were isolated from the rhizosphere of jujube and were identified by 16S rDNA sequencing analysis. Then, the isolates were screened for drought tolerance and plant growth promoting activities. The growth and physiological changes of jujube under drought stress, including the plant height, shoot and root dry matter, malondialdehyde (MDA), indoleacetic acid (IAA), abscisic acid (ABA) content, superoxide dismutase (SOD), and peroxidase (POD) activity, were also detected. Eight ACC deaminase-producing bacterial strains were isolated and identified as Pseudomonas, Bacillus, and Serratia. Under drought stress conditions, Pseudomonas lini and Serratia plymuthica significantly increased plant height, shoot and root dry matter, and relative water content. Moreover, malondialdehyde and ABA levels were decreased, and antioxidant enzyme activities were increased. In addition, they also enhanced soil aggregate stability. The best effect was observed with mixed inoculation. Strains of Pseudomonas lini and Serratia plymuthica played an important role in enhancing tolerance of jujube seedling and can be considered as promising bioinoculants of jujube.

中文翻译：

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从枣（Ziziphus jujuba）中分离的耐旱植物促生长根际细菌及其增强耐旱性的潜力

植物生长促进根际细菌（PGPR）在改善植物生长和减轻干旱胁迫条件下胁迫诱导的损害方面具有重要作用。本研究的目的是：1）从半干旱和干旱地区生长的耐旱植物枣根际土壤中分离和鉴定耐旱PGPR；2) 评价在干旱胁迫条件下接种分离株对枣幼苗生长和生理反应的影响。从枣的根际中分离出具有 1-氨基环丙烷-1-羧酸 (ACC) 脱氨酶活性的根际细菌，并通过 16S rDNA 测序分析进行鉴定。然后，筛选分离株的耐旱性和植物生长促进活性。干旱胁迫下枣树的生长及生理变化，还检测了包括株高、地上部和根部干物质、丙二醛（MDA）、吲哚乙酸（IAA）、脱落酸（ABA）含量、超氧化物歧化酶（SOD）和过氧化物酶（POD）活性。八株产 ACC 脱氨酶的菌株被分离并鉴定为假单胞菌、芽孢杆菌和沙雷氏菌。在干旱胁迫条件下，Pseudomonas lini 和 Serratia plymuthica 显着增加了植物高度、芽和根干物质以及相对含水量。此外，丙二醛和ABA水平降低，抗氧化酶活性增加。此外，它们还增强了土壤团聚体的稳定性。混合接种观察到最佳效果。