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As the main economic crop cultivated in the Yellow River Delta, winter jujube contains various nutrients. However, soil salinization and fungal diseases have affected the yield and quality of winter jujube. In order to use plant growth-promoting rhizobacteria (PGPR) to reduce these damages, the antagonistic bacteria CZ-6 isolated from the rhizosphere of wheat in saline soil was selected for experiment. Gene sequencing analysis identified CZ-6 as Bacillus amyloliquefaciens. In order to understand the salt tolerant and disease-resistant effects of CZ-6 strain, determination of related indicators of salt tolerance, pathogen antagonistic tests, and anti-fungal mechanism analyses was carried out. A pot experiment was conducted to evaluate the effect of CZ-6 inoculation on the rhizosphere microbial community of winter jujube. The salt tolerance test showed that CZ-6 strain can survive in a medium with a NaCl concentration of 10% and produces indole acetic acid (IAA) and 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase. Studies on the inhibition mechanism of pathogenic fungi show that CZ-6 can secrete cellulase, protease, and xylanase. Gas chromatography-mass spectrometry (GC-MS) analysis showed that CZ-6 can release volatile organic compounds (VOCs), including 2-heptanone and 2-nonanone. In addition, the strain can colonize the rhizosphere and migrate to the roots, stems, and leaves of winter jujube, which is essential for plant growth or defense against pathogens. Illumina MiSeq sequencing data indicated that, compared to the control, the abundance of salt-tolerant bacteria Tausonia in the CZ-6 strain treatment group was significantly increased, while the richness of Chaetomium and Gibberella pathogens was significantly reduced. Our research shows that CZ-6 has the potential as a biological control agent in saline soil. Plant damage and economic losses caused by pathogenic fungi and salt stress are expected to be alleviated by the addition of salt-tolerant antagonistic bacteria.

As the main economic crop cultivated in the Yellow River Delta, winter jujube contains various nutrients. However, soil salinization and fungal diseases have affected the yield and quality of winter jujube. In order to use plant growth-promoting rhizobacteria (PGPR) to reduce these damages, the antagonistic bacteria CZ-6 isolated from the rhizosphere of wheat in saline soil was selected for experiment. Gene sequencing analysis identified CZ-6 as Bacillus amyloliquefaciens. In order to understand the salt tolerant and disease-resistant effects of CZ-6 strain, determination of related indicators of salt tolerance, pathogen antagonistic tests, and anti-fungal mechanism analyses was carried out. A pot experiment was conducted to evaluate the effect of CZ-6 inoculation on the rhizosphere microbial community of winter jujube. The salt tolerance test showed that CZ-6 strain can survive in a medium with a NaCl concentration of 10% and produces indole acetic acid (IAA) and 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase. Studies on the inhibition mechanism of pathogenic fungi show that CZ-6 can secrete cellulase, protease, and xylanase. Gas chromatography-mass spectrometry (GC-MS) analysis showed that CZ-6 can release volatile organic compounds (VOCs), including 2-heptanone and 2-nonanone. In addition, the strain can colonize the rhizosphere and migrate to the roots, stems, and leaves of winter jujube, which is essential for plant growth or defense against pathogens. Illumina MiSeq sequencing data indicated that, compared to the control, the abundance of salt-tolerant bacteria Tausonia in the CZ-6 strain treatment group was significantly increased, while the richness of Chaetomium and Gibberella pathogens was significantly reduced. Our research shows that CZ-6 has the potential as a biological control agent in saline soil. Plant damage and economic losses caused by pathogenic fungi and salt stress are expected to be alleviated by the addition of salt-tolerant antagonistic bacteria.

Biocontrol by inoculation with beneficial microbes is a proven strategy for reducing the negative effect of soil-borne pathogens. We evaluated the effects of microbial inoculants BIO-1 and BIO-2 in reducing soil-borne wheat diseases and in influencing wheat rhizosphere microbial community composition in a plot test. The experimental design consisted of three treatments: (1) Fusarium graminearum F0609 (CK), (2) F. graminearum + BIO-1 (T1), and (3) F. graminearum F0609 + BIO-2 (T2). The results of the wheat disease investigation showed that the relative efficacies of BIO-1 and BIO-2 were up to 82.5% and 83.9%, respectively. Illumina MiSeq sequencing revealed that bacterial abundance and diversity were significantly higher ( P < 0.05 ) in the treatment groups (T1 and T2) than in the control, with significantly decreased fungal diversity in the T2 group. Principal coordinates and hierarchical clustering analyses revealed that the bacterial and fungal communities were distinctly separated between the treatment and control groups. Bacterial community composition analysis demonstrated that beneficial microbes, such as Sphingomonas, Bacillus, Nocardioides, Rhizobium, Streptomyces, Pseudomonas, and Microbacterium, were more abundant in the treatment groups than in the control group. Fungal community composition analysis revealed that the relative abundance of the phytopathogenic fungi Fusarium and Gibberella decreased and that the well-known beneficial fungi Chaetomium, Penicillium, and Humicola were more abundant in the treatment groups than in the control group. Overall, these results confirm that beneficial microbes accumulate more easily in the wheat rhizosphere following application of BIO-1 and BIO-2 and that the relative abundance of phytopathogenic fungi decreased compared with that in the control group.

The present study investigated the physiological and biochemical characteristics of Enterobacter cloacae HG-1 isolated from saline-alkali soil. We further studied the effect of this strain on the salt tolerance of wheat and on the community structure of nitrogen-fixing bacteria in rhizosphere soil. We determined that the investigated strain had high nitrogen fixation activity and produced iron carriers, 1-aminocyclopropane-1-carboxylic acid deaminase, and plant hormones. The metabolites of this strain contained 2,3-butanediol, [R-(R*, R*)], 2-heptanone, and other growth-promoting and antibacterial substances. The strain was also highly salt-tolerant (10% NaCl). After the inoculation of wheat with the HG-1 strain, we recorded increases in root length, plant height, fresh weight, and dry weight of 19.15%, 18.83%, 16.67%, and 17.96%, respectively, compared with uninoculated plants (P < 0.05). Compared with the leaves of uninoculated plants, the proline concentration in the leaves of inoculated plants increased by 12.43% (P < 0.05), the malondialdehyde level decreased by 27.26% (P < 0.05), K+ increased by 20.69%, Ca2+ increased by 57.53% and Na+ decreased by 31.43% (all P