The Effect of Salt-Tolerant Antagonistic Bacteria CZ-6 on the Rhizosphere Microbial Community of Winter Jujube (Ziziphus jujuba Mill. “Dongzao”) in Saline-Alkali Land

Abstract

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.

Effect of Zinc Oxide Nanoparticles on the Growth of Malus hupehensis Rehd. Seedlings

“…It has been reported that the addition of biochar to the soil had a mitigating effect on eggplant Verticillium wilt, among which Tausonia, Chaetomium, Mortierella, and Humicola were the dominant fungi, indicating that they may play a positive role in disease suppression (Ogundeji et al, 2021). After Zhou et al (2021) added antagonistic bacteria to the soil of winter jujube (Ziziphus jujuba Mill. "Dongzao") with Botrytis cinerea, Botryosphaeria dothidea, and Colletotrichum gloeosporioides, the relative abundance of Tausonia also increased significantly.…”

Plant growth-promoting rhizobacteria (PGPR) and its mechanisms against plant diseases for sustainable agriculture and better productivity

“…These bioactive secondary metabolites are encoded by biosynthetic gene clusters (BGCs) and classified as ribosomally synthesized peptides, non-ribosomally synthesized peptides and polyketide synthases (Kenawy et al, 2019). PGPR strains such as Bacillus and Paenibacillus isolated from rhizosphere of tomato plants showed strong antagonistic activity against tomato bacterial, fungal and oomycetal pathogens and the compounds were found to be surfactin, fengycin, bacillibactin, petrobactin, lichenysin and bacillaene (Zhou et al, 2021). Wang et al (2021) suggested that PGPR consortium proved to protect the crops from various diseases rather individual strains of PGPR.…”

Enhancing Resistance to Salinity in Wheat by Using Streptomyces sp. HU2014

“…Many studies have shown that Trichoderma spp., Bacillus spp., Pseudomonas spp., and Streptomyces spp. can protect plants against salt stress and promote plant growth [21][22][23][24]. The mechanisms of these microbes enhancing salt tolerance include producing bioactive metabolites, inducing plant system resistance, and enhancing microbial community structure in the plant rhizosphere.…”

“…Berg et al proposed that the pathogenic and beneficial microbes in the microbial community were interdependent and dynamically changing [29]. Bacillus amyloliquefaciens CZ-6 inoculation remarkably increased salt-tolerant Tausonia while decreasing Chaetomium and Gibberella pathogens in winter jujube rhizosphere soil [23]. The structural adjustment of rhizospheric microorganisms coexists harmoniously with the plants in salt conditions.…”