Dataset Information

The Soil Nutrient Environment Determines the Strategy by Which Bacillus velezensis HN03 Suppresses Fusarium wilt in Banana Plants.

ABSTRACT: Biological control agents (BCAs) are considered as one of the most important strategies for controlling Fusarium wilt, and bioorganic fertilizer, in particular, has been extensively investigated. However, little is known regarding how a biocontrol microorganism affects the suppression mechanisms when combined with different amendments. In this study, a pot experiment was performed using banana plants to investigate the different mechanisms by which the biocontrol bacterium Bacillus velezensis HN03 (isolated from our laboratory) and amendments suppress Fusarium wilt. The incidence of banana wilt was decreased under HN03 and was reduced further when HN03 was combined with compost, particularly wormcast. In the suppression of Fusarium wilt, HN03 was found to influence the soil environment in various ways. HN03 increased the peroxidase level, which improves plant defense, and was highest when combined with wormcast, being 69 times higher than when combined with cow dung compost. The high accumulation of Mg and P in the "HN03 + wormcast" and Zn and Mn in the "HN03 + cow dung" treatments was negatively correlated with disease incidence. Furthermore, HN03 re-established the microbial community destroyed by the pathogen and further increased the level of suppression in the wormcast. HN03 also enhanced the functional traits of the soil, including defensive mechanism-related traits, and these traits were further enhanced by the combination of HN03 + wormcast.

SUBMITTER: Wu X

PROVIDER: S-EPMC7701294 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature

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The Soil Nutrient Environment Determines the Strategy by Which Bacillus velezensis HN03 Suppresses Fusarium wilt in Banana Plants.

Wu Xiaoyan X Shan Ying Y Li Yi Y Li Qinfen Q Wu Chunyuan C

Frontiers in plant science 20201116

Biological control agents (BCAs) are considered as one of the most important strategies for controlling Fusarium wilt, and bioorganic fertilizer, in particular, has been extensively investigated. However, little is known regarding how a biocontrol microorganism affects the suppression mechanisms when combined with different amendments. In this study, a pot experiment was performed using banana plants to investigate the different mechanisms by which the biocontrol bacterium Bacillus vel ...[more]

PMID: 33304372

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Project description:Cucumber Fusarium wilt, caused by Fusarium oxysporum, is a devastating disease of cucumber and leads to enormous economic losses worldwide. The antagonistic bacterium Bacillus velezensis NH-1 suppresses F. oxysporum For a higher biological control effect, control-released microcapsules of NH-1 were prepared using cell immobilization technology. NH-1 cells were embedded in combinations of the biodegradable wall materials sodium alginate, chitosan, and cassava-modified starch to prepare control-released microbiological microcapsules. For the preparation of alginate single-layer microcapsules, the highest embedding rate of 72.60% was obtained by applying 3% sodium alginate and 2% calcium chloride. After the application of monolayer alginate microcapsules in soil, the number of bacterial cells corresponded to a sustained release curve, and the survival rate of NH-1 was higher than the control in which soil was directly irrigated with NH-1 broth. The use of 0.8% chitosan (pH 3.0) and 0.5% cassava-modified starch in the preparation of double-layer and triple-layer microcapsules changed the performance of the microcapsules and increased the embedding rate. After dry storage for 65 days, the number of NH-1 cells was at the highest level in the monolayer microcapsules. In the field experiment, the control efficiency of alginate-coated monolayer microcapsules on Fusarium wilt was 100%, which was significantly higher than for the NH-1 culture and double-layer and triple-layer microcapsules. Collectively, sodium alginate is an ideal wall material for preparing slow-release bacterial microcapsules to control cucumber Fusarium wilt. Monolayer alginate microcapsules retard the release of B. velezensis NH-1 in soils and significantly improve its biocontrol efficiency on cucumber Fusarium wilt.IMPORTANCEBacillus species are often used for the biocontrol of various plant pathogens, but the control efficiency of Bacillus is usually unstable in field experiments. To improve the control efficiency of Bacillus, in this study, microcapsules of Bacillus velezensis strain NH-1 were prepared using different wall materials (sodium alginate, chitosan, and cassava-modified starch). It was found that the control efficiency of alginate-coated monolayer microcapsules on Fusarium wilt was 100% in field experiments, which was higher than for NH-1 culture and double-layer and triple-layer microcapsules. This study provides a new approach for preparing a biocontrol agent against Fusarium wilt with high biocontrol efficiency.

Project description:BackgroundPlant microbiome highlights the importance of endosphere microbiome for growth and health of the host plant. Microbial community analysis represents an elegant way to identify keystone microbial species that have a more central position in the community. The aim of this study was to access the interactions between the keystone bacterial species and plants during banana Fusarium wilt process, by comparing the endophytic bacterial and fungal community in banana roots and shoot tips during growth and wilting processes. The keystone bacterial species were isolated and further engineered to improve banana wilt resistance.ResultsBanana endosphere microbiome structure varied during plant growth and wilting processes. Bacterial and fungal diversity in the shoot tips and roots increased with the development of the banana plantlets. The bacterial groups belonging to the Enterobacteriaceae family with different relative abundances were detected in all the samples. The Klebsiella spp. might be the keystone bacteria during the growth of banana plantlets. The relative abundance of Fusarium associated with the wilt disease did not increase during the wilting process. The endophytic Enterobacteriaceae strains Enterobacter sp. E5, Kosakonia sp. S1, and Klebsiella sp. Kb were isolated on Enterobacteriaceae selective medium and further engineered by expressing 1-aminocyclopropane-1-carboxylate (ACC) deaminase on the bacterial cell walls (designated as E5P, S1P, and KbP, respectively). Pot experiments suggested that plants inoculated with strains E5, E5P, S1, and S1P increased resistance to the Fusarium wilt disease compared with the controls without inoculation, whereas the Klebsiella inoculation (Kb and KbP) did not increase the wilt resistance. Compared with the inoculation with the wild strains E5 and S1, the inoculation with engineered strains E5P and S1P significantly increased wilt resistance and promoted plant growth, respectively. The results illustrated that the keystone species in the banana microbiome may not be dominant in numbers and the functional role of keystone species should be involved in the wilt resistance.ConclusionThe ACC deaminase activity of engineered bacteria was essential to the Fusarium wilt resistance and growth promotion of banana plants. Engineering keystone bacteria in plant microbiome with ACC deaminase on the cell walls should be a promising method to improve plant growth and disease resistance.

Project description:In the last century, the banana crop and industry experienced dramatic losses due to an epidemic of Fusarium wilt of banana (FWB), caused by Fusarium oxysporum f.sp. cubense (Foc) race 1. An even more dramatic menace is now feared due to the spread of Foc tropical race 4. Plant genetic resistance is generally considered as the most plausible strategy for controlling effectively such a devastating disease, as occurred for the first round of FWB epidemic. Nevertheless, with at least 182 articles published since 1970, biological control represents a large body of knowledge on FWB. Remarkably, many studies deal with biological control agents (BCAs) that reached the field-testing stage and even refer to high effectiveness. Some selected BCAs have been repeatedly assayed in independent trials, suggesting their promising value. Overall under field conditions, FWB has been controlled up to 79% by using Pseudomonas spp. strains, and up to 70% by several endophytes and Trichoderma spp. strains. Lower biocontrol efficacy (42-55%) has been obtained with arbuscular mycorrhizal fungi, Bacillus spp., and non-pathogenic Fusarium strains. Studies on Streptomyces spp. have been mostly limited to in vitro conditions so far, with very few pot-experiments, and none conducted in the field. The BCAs have been applied with diverse procedures (e.g., spore suspension, organic amendments, bioformulations, etc.) and at different stages of plant development (i.e., in vitro, nursery, at transplanting, post-transplanting), but there has been no evidence for a protocol better than another. Nonetheless, new bioformulation technologies (e.g., nanotechnology, formulation of microbial consortia and/or their metabolites, etc.) and tailor-made consortia of microbial strains should be encouraged. In conclusion, the literature offers many examples of promising BCAs, suggesting that biocontrol can greatly contribute to limit the damage caused by FWB. More efforts should be done to further validate the currently available outcomes, to deepen the knowledge on the most valuable BCAs, and to improve their efficacy by setting up effective formulations, application protocols, and integrated strategies.

Project description:One major issue in reducing cucumber yield is the destructive disease Cucumber (Cucumis sativus L.) wilt disease caused by Fusarium oxysporum f. sp. cucumerinum (Foc). When using the isolate VJH504 isolated from cucumber rhizosphere soil and identified as Bacillus velezensis, the growth of Foc in the double culture experiment was effectively inhibited. Phenotypic, phylogenetic, and genomic analyses were conducted to enhance understanding of its biocontrol mechanism. According to the result of the phenotype analysis, B. velezensis VJH504 could inhibit cucumber fusarium wilt disease both in vitro and in vivo, and significantly promote cucumber seed germination and seedling growth. Additionally, the tests of growth-promoting and biocontrol characteristics revealed the secretion of proteases, amylases, β-1,3-glucanases, cellulases, as well as siderophores and indole-3-acetic acid by B. velezensis VJH504. Using the PacBio Sequel II system, we applied the complete genome sequencing for B. velezensis VJH504 and obtained a single circular chromosome with a size of 3.79 Mb. A phylogenetic tree was constructed based on the 16S rRNA gene sequences of B. velezensis VJH504 and 13 other Bacillus species, and Average Nucleotide Identity (ANI) analysis was performed using their whole-genome sequences, confirming isolateVJH504 as B. velezensis. Following this, based on the complete genome sequence od B. velezensis VJH504, specific functional analysis, Carbohydrate-Active Enzymes (CAZymes) analysis, and secondary metabolite analysis were carried out, predicting organism's abilities for biofilm formation, production of antifungal CAZymes, and synthesis of antagonistic secondary metabolites against pathogens. Afterwards, a comparative genomic analysis was performed between B. velezensis VJH504 and three other B. velezensis strains, revealing subtle differences in their genomic sequences and suggesting the potential for the discovery of novel antimicrobial substances in B. velezensis VJH504. In conclusion, the mechanism of B. velezensis VJH504 in controlling cucumber fusarium wilt was predicted to appear that B. velezensis VJH504is a promising biocontrol agent, showcasing excellent application potential in agricultural production.

Dataset Information

The Soil Nutrient Environment Determines the Strategy by Which Bacillus velezensis HN03 Suppresses Fusarium wilt in Banana Plants.

Publications

The Soil Nutrient Environment Determines the Strategy by Which <i>Bacillus velezensis</i> HN03 Suppresses <i>Fusarium</i> wilt in Banana Plants.

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