Bacterial community composition of wheat aboveground compartments correlates with yield during the reproductive phase.

Plant-associated microbial communities play important roles in agricultural productivity, and their composition has been shown to vary across plant compartments and developmental stages. However, the response of microbial communities within different plant compartments and at different developmental stages to diverse long-term fertilization treatments, as well as their linkages with crop yields, remains underexplored. This study analyzed wheat-associated bacterial communities within various soil and plant compartments under three fertilization treatments throughout the vegetative and reproductive phases. The variance in bacterial community was primarily attributed to compartments, followed by fertilization treatments and developmental stages. The composition of belowground bacterial communities (bulk soil, rhizosphere soil, and root) exhibited stronger responses to fertilization treatments than aboveground compartments (stem and leaf). The composition of belowground bacterial communities responded to fertilization treatments at all developmental stages, and it was significantly correlated with crop yields during the vegetative phase, whereas the aboveground community composition only showed a response to fertilization during the reproductive phase, at which point it was significantly correlated with crop yields. Moreover, during this reproductive phase, the co-occurrence network of aboveground bacterial communities exhibited enhanced complexity, and it contained an increased number of keystone species associated with crop yields, such as Sphingomonas spp., Massilia spp., and Frigoribacterium spp. Structural equation modeling indicated that augmenting total phosphorus levels in aboveground compartments could enhance crop yields by increasing the relative abundance of these keystone species during the reproductive phase. These findings highlight the pivotal role of aboveground bacterial communities in wheat production during the reproductive phase. IMPORTANCE: The developmental stage significantly influences crop-associated bacterial communities, but the relative importance of bacterial communities in different compartments to crop yields across various stages is still not well understood. This study reveals that belowground bacterial communities during the vegetative phase are significantly correlated with crop yields. Notably, during the reproductive phase, the composition of aboveground bacterial communities was significantly correlated with crop yields. During this phase, the complexity and enriched keystone species within the aboveground co-occurrence network underscore their role in boosting crop production. These results provide a foundation for developing microbiome-based products that are phase-specific and promote sustainable agricultural practices.

Non-selective microbiota reduction after the elicitation of a seaweed's immune response.

Pattern-triggered immunity (PTI) is an integral part of the innate immune system of many eukaryotic hosts, assisting in the defence against pathogen invasions. In plants and animals, PTI exerts a selective pressure on the microbiota that can alter community composition. However, the effect of PTI on the microbiota for non-model hosts, including seaweeds, remains unknown. Using quantitative polymerase chain reaction complemented with 16S rRNA gene and transcript amplicon sequencing, this study profiled the impact that PTI of the red seaweed Gracilaria gracilis has on its microbiota. PTI elicitation with agar oligosaccharides resulted in a significant reduction in the number of bacteria (by >75% within 72 h after treatment). However, the PTI elicitation did not cause any significant difference in the community diversity or structure. These findings demonstrated that PTI can be non-selective, and this might help to maintain a stable microbiota by uniformly reducing bacterial loads.

A pathway to improve seaweed aquaculture through microbiota manipulation.

Eukaryotic hosts are associated with microbial communities that are critical to their function. Microbiota manipulation using beneficial microorganisms, for example, in the form of animal probiotics or plant growth-promoting microorganisms (PGPMs), can enhance host performance and health. Recently, seaweed beneficial microorganisms (SBMs) have been identified that promote the growth and development and/or improve disease resistance of seaweeds. This knowledge coincides with global initiatives seeking to expand and intensify seaweed aquaculture. Here, we provide a pathway with the potential to improve commercial cultivation of seaweeds through microbiota manipulation, highlighting that seaweed restoration practices can also benefit from further understanding SBMs and their modes of action. The challenges and opportunities of different approaches to identify and apply SBMs to seaweed aquaculture are discussed.

Bacterial controlled mitigation of dysbiosis in a seaweed disease.

Disease in the marine environment is predicted to increase with anthropogenic stressors and already affects major habitat-formers, such as corals and seaweeds. Solutions to address this issue are urgently needed. The seaweed Delisea pulchra is prone to a bleaching disease, which is caused by opportunistic pathogens and involves bacterial dysbiosis. Bacteria that can inhibit these pathogens and/or counteract dysbiosis are therefore hypothesised to reduce disease. This study aimed to identify such disease-protective bacteria and investigate their protective action. One strain, Phaeobacter sp. BS52, isolated from healthy D. pulchra, was antagonistic towards bleaching pathogens and significantly increased the proportion of healthy individuals when applied before the pathogen challenge (pathogen-only vs. BS52 + pathogen: 41-80%), and to a level similar to the control. However, no significant negative correlations between the relative abundances of pathogens and BS52 on D. pulchra were detected. Instead, inoculation of BS52 mitigated pathogen-induced changes in the epibacterial community. These observations suggest that the protective activity of BS52 was due to its ability to prevent dysbiosis, rather than direct pathogen inhibition. This study demonstrates the feasibility of manipulating bacterial communities in seaweeds to reduce disease and that mitigation of dysbiosis can have positive health outcomes.

Cross-Host Protection of Marine Bacteria Against Macroalgal Disease.

Despite an increasing awareness of disease impacts on both cultivated and native seaweed populations, the development of marine probiotics has been limited and predominately focused on farmed animals. Bleaching (loss of thallus pigmentation) is one of the most prevalent diseases observed in marine macroalgae. Endemic probiotic bacteria have been characterized to prevent bleaching disease in red macroalgae Agarophyton vermiculophyllum and Delisea pulchra; however, the extent to which probiotic strains provide cross-protection to non-endemic hosts and the influence of native microbiota remain unknown. Using A. vermiculophyllum as a model, we demonstrate that co-inoculation with the pathogen Pseudoalteromonas arctica G-MAN6 and D. pulchra probiotic strain Phaeobacter sp. BS52 or Pseudoalteromonas sp. PB2-1 reduced the disease risks compared to the pathogen only treatment. Moreover, non-endemic probiotics outperformed the endemic probiotic strain Ralstonia sp. G-NY6 in the presence of the host natural microbiota. This study highlights how the native microbiota can impact the effectiveness of marine probiotics and illustrates the potential of harnessing probiotics that can function across different hosts to mitigate the impact of emerging marine diseases.

[Isolation and Identification of Antagonistic Endophytic Actinomycetes Against Root Rot Disease in Ligusticum chuanxiong].

Objective: To get an understanding of the microflora of endophytic actinomycetes in Ligusticum chuanxiong,and to obtain the resource of antagonistic strains against Ligusticum chuanxiong root rot disease. Methods: Actinomycetes in stem nodes and rhizomes of Ligusticum chuanxiong were isolated and purified by a series of means,namely tissue block method, homogenate technique and plat streaking method. Further, dual culture and inhibition zone method were employed to test the antagonistic activity of these strains. To identify strains with potential precisely,both microscopic observation and DNA sequencing were conducted. Results: 83 strains of Ligusticum chuanxiong endophytic actinomycetes were identified, which consisted of 13 species groups. Among all of them,species identified as Streptomyces scopuliridis( KF600747. 1), Streptomyces griseorubiginosus( AB706352. 1) and Streptomyces agglomeratus( LC055413. 1) showed antagonistic activities against four kinds of pathogenic fungi of Ligusticum chuanxiong root rot disease. Conclusion: Actinomycetes which belong to Griseorubroviolaceus groups of streptomyce are potential biocontrol microbes to Ligusticum chuanxiong root rot,showing importance to the production of Chuanxiong Rhizoma.

[Identification of Pathogens Causing Root Rot Disease on Ligusticum chuanxiong in Sichuan].

OBJECTIVE: To identify the pathogens causing root rot disease on Ligusticum chuanxiong from the main producing areas in Sichuan, and to provide gist of management of this disease in the future. METHODS: The diseased rhizomes of Ligusticurn chuanxiong with root rot symptom were sampled in two main producing areas in Sichuan. According to Koch's postulate, the pathogenicity on Ligusticum chuanxiong rhizomes of the isolates was confirmed. The representative isolates were identified based on their morphological characteristics and ribosomal DNA internal transcribed spacer(rDNA-ITS) sequences. RESULTS: The isolates(f2-16, 3-2, f4-19 and f5-7)which caused root rot disease held high homology reached 99%, 99%, 100% and 100% respectively, when compared with GenBank sequences GQ229075, JQ796755, JN232136 and FJ481024. CONCLUSION: The causing agents of root rot disease on Ligusticum chuanxiong belong to Fusarium solani, Fusarium oxysporum, Plectosphaerella cucumerina and Phoma glomerata. Pathogens from different regions are varied.