Aim
Trichoderma guizhouense
NJAU 4742 (Tgui) can serve as a promising strain for the development of novel biofertilizers and biofungicides. Plants primed with Tgui via inoculation were investigated ...to clarify the underlying mechanisms that promote root growth and development and activate the plant innate immune response.
Methods
The relative expression of defence-related genes and of genes involved in the auxin signalling pathway in
Zea mays
and
Arabidopsis thaliana
was quantified. Scanning electron microscopy (SEM) was performed to visualize the colonization of Tgui in maize roots, and a proteomic approach was used to identify Tgui-derived elicitors.
Results
The establishment of Tgui in the rhizosphere of maize leads to the stimulation of the auxin synthesis pathway in maize and subsequently leads to increased plant growth. And the extracellular proteins of Tgui induced systemic resistance (ISR) of maize plants to
Fusarium verticillioides
(Fv) (Hypocreales, Ascomycota); the ISR of maize plants may be linked to the accumulation of reactive oxygen species (ROS) and increased deposition of callose in maize tissue.
Conclusions
Activation of the maize immune response was triggered by the mixture of extracellular proteins secreted by Tgui into the rhizosphere. Our study thereby contributes to a better understanding of the interaction between
T. guizhouense
and plant roots.
Agricultural production continues to be constrained by a number of biotic and abiotic factors that can reduce crop yield quantity and quality. Potassium (K) is an essential nutrient that affects most ...of the biochemical and physiological processes that influence plant growth and metabolism. It also contributes to the survival of plants exposed to various biotic and abiotic stresses. The following review focuses on the emerging role of K in defending against a number of biotic and abiotic stresses, including diseases, pests, drought, salinity, cold and frost and waterlogging. The availability of K and its effects on plant growth, anatomy, morphology and plant metabolism are discussed. The physiological and molecular mechanisms of K function in plant stress resistance are reviewed. This article also evaluates the potential for improving plant stress resistance by modifying K fertilizer inputs and highlights the future needs for research about the role of K in agriculture.
Bacteriophages have been proposed as an alternative to pesticides to kill bacterial pathogens of crops. However, the efficacy of phage biocontrol is variable and poorly understood in natural ...rhizosphere microbiomes. We studied biocontrol efficacy of different phage combinations on Ralstonia solanacearum infection in tomato. Increasing the number of phages in combinations decreased the incidence of disease by up to 80% in greenhouse and field experiments during a single crop season. The decreased incidence of disease was explained by a reduction in pathogen density and the selection for phage-resistant but slow-growing pathogen strains, together with enrichment for bacterial species that were antagonistic toward R. solanacearum. Phage treatment did not affect the existing rhizosphere microbiota. Specific phage combinations have potential as precision tools to control plant pathogenic bacteria.
Soil-borne plant diseases are increasingly causing devastating losses in agricultural production. The development of a more refined model for disease prediction can aid in reducing crop losses ...through the use of preventative control measures or soil fallowing for a planting season. The emergence of high-throughput DNA sequencing technology has provided unprecedented insight into the microbial composition of diseased versus healthy soils. However, a single independent case study rarely yields a general conclusion predictive of the disease in a particular soil. Here, we attempt to account for the differences among various studies and plant varieties using a machine-learning approach based on 24 independent bacterial data sets comprising 758 samples and 22 independent fungal data sets comprising 279 samples of healthy or Fusarium wilt-diseased soils from eight different countries. We found that soil bacterial and fungal communities were both clearly separated between diseased and healthy soil samples that originated from six crops across nine countries or regions. Alpha diversity was consistently greater in the fungal community of healthy soils. While diseased soil microbiomes harbored higher abundances of Xanthomonadaceae, Bacillaceae, Gibberella, and Fusarium oxysporum, the healthy soil microbiome contained more Streptomyces Mirabilis, Bradyrhizobiaceae, Comamonadaceae, Mortierella, and nonpathogenic fungi of Fusarium. Furthermore, a random forest method identified 45 bacterial OTUs and 40 fungal OTUs that categorized the health status of the soil with an accuracy >80%. We conclude that these models can be applied to predict the potential for occurrence of F. oxysporum wilt by revealing key biological indicators and features common to the wilt-diseased soil microbiome.
It is important to study the response of plant pathogens to the antibiosis traits of biocontrol microbes to design the efficient biocontrol strategies. In this study, we evaluated the role of ...volatile organic compounds (VOCs) produced by a biocontrol strain Bacillus amyloliquefaciens SQR-9 on the growth and virulence traits of tomato wilt pathogen Ralstonia solanacearum (RS). The VOCs of SQR-9 significantly inhibited the growth of RS on agar medium and in soil. In addition, the VOCs significantly inhibited the motility traits, production of antioxidant enzymes and exopolysaccharides, biofilm formation and tomato root colonization by RS. The strain SQR-9 produced 22 VOCs, but only nine VOCs showed 1-11% antibacterial activity against RS in their corresponding amounts; however, the consortium of all VOCs showed 70% growth inhibition of RS. The proteomics analysis showed that the VOCs of SQR-9 downregulated RS proteins related to the antioxidant activity, virulence, carbohydrate and amino acid metabolism, protein folding and translation, while the proteins involved in the ABC transporter system, amino acid synthesis, detoxification of aldehydes and ketones, methylation, protein translation and folding, and energy transfer were upregulated. This study describes the significance and effectiveness of VOCs produced by a biocontrol strain against tomato wilt pathogen.
Nitrogen (N) and carbon (C) are essential elements for plant growth and crop yield. Thus, improved N and C utilisation contributes to agricultural productivity and reduces the need for fertilisation. ...In the present study, we find that overexpression of a single rice gene, Oryza sativa plasma membrane (PM) H
-ATPase 1 (OSA1), facilitates ammonium absorption and assimilation in roots and enhanced light-induced stomatal opening with higher photosynthesis rate in leaves. As a result, OSA1 overexpression in rice plants causes a 33% increase in grain yield and a 46% increase in N use efficiency overall. As PM H
-ATPase is highly conserved in plants, these findings indicate that the manipulation of PM H
-ATPase could cooperatively improve N and C utilisation, potentially providing a vital tool for food security and sustainable agriculture.
•Manure generation in China is increasing with demand for livestock products.•More livestock are being reared in concentrated animal feeding operations (CAFOs).•Poor manure containment and discharge ...into watercourses causes environmental damage.•Manure nutrient use is limited by inadequate infrastructure, knowledge and labour.•Strategic planning of nutrients is required at farm-, regional- and national-scale.
Traditionally farmers in China have relied on organic manures to build the organic matter content in soil and to fertilise crops for both human and livestock consumption. However, with requirements to increase food production, the use of relatively cheap inorganic fertilisers has increased, and manure nutrients are not always used to their potential. In addition, farms of all sizes and even biogas plants, often lack the basic infrastructure to manage manures; poor containment facilities often result in untreated manures being discharged directly into watercourses, whilst transportation of manures to the field and land spreading is often not mechanised and relies on availability of suitable labour. There is already clear evidence of overuse of nutrients in some parts of China and this is causing undesirable impacts on the environment. With the increasing demand for livestock products from a burgeoning population and changes in dietary preferences towards animal protein, greater quantities of manure nutrients will be generated in the next twenty years, especially in peri-urban concentrated animal feeding operations and intensive farms. It is essential that China addresses the infrastructural, research and communication challenges to ensure that manures are integrated into nutrient planning at the field, farm and regional level to safeguard the environment, reduce the requirement for inorganic fertiliser production and use, and improve farmer incomes. This paper reviews the current manure management practices, both nationally and, where appropriate, at a regional scale, and assesses what barriers currently prevent efficient manure nutrient utilisation in China. We then address the future challenges for manure nutrient management in China, before summarising key gaps in knowledge and communication with implications for research and policy.
Nitrogen (N) is one of the most important elements that has a central impact on plant growth and yield. N is also widely involved in plant stress responses, but its roles in host-pathogen ...interactions are complex as each affects the other. In this review, we summarize the relationship between N nutrition and plant disease and stress its importance for both host and pathogen. From the perspective of the pathogen, we describe how N can affect the pathogen's infection strategy, whether necrotrophic or biotrophic. N can influence the deployment of virulence factors such as type III secretion systems in bacterial pathogen or contribute nutrients such as gamma-aminobutyric acid to the invader. Considering the host, the association between N nutrition and plant defence is considered in terms of physical, biochemical and genetic mechanisms. Generally, N has negative effects on physical defences and the production of anti-microbial phytoalexins but positive effects on defence-related enzymes and proteins to affect local defence as well as systemic resistance. N nutrition can also influence defence via amino acid metabolism and hormone production to affect downstream defence-related gene expression via transcriptional regulation and nitric oxide (NO) production, which represents a direct link with N. Although the critical role of N nutrition in plant defences is stressed in this review, further work is urgently needed to provide a comprehensive understanding of how opposing virulence and defence mechanisms are influenced by interacting networks.
Worldwide, banana production is severely hindered by Fusarium wilt, a devastating disease caused by the soil-borne fungus Fusarium oxysporum f. sp. cubense (Foc). With no widely adopted efficient ...method of control or prevention, the emergence of a new Foc variant, tropical race 4 (Foc TR4), has led to the widespread destruction of plantations in Cavendish-producing areas. Recently, banana Fusarium wilt has been controlled by the consecutive application of biofertilizer (BIO) in newly reclaimed fields. In this study we examine the temporal effects of BIO versus compost application in newly converted banana fields on the composition and abundance of the rhizosphere bacterial and fungal communities and the survival of the biocontrol inoculant, Bacillus amyloliquefaciens NJN-6. Our findings show that BIO-amended rhizosphere soils increased the abundance of bacteria while decreasing fungal abundance. This corresponded to higher bacterial richness and diversity in the BIO amendment, while no trends were observed with the fungal community. Rhizosphere soil bacterial and fungal community composition were significantly different between BIO and compost amendment and treatment, not time, exhibited the largest impact. Other potential taxa involved in disease suppression were also identified, such as increased abundances of Sphingobium, Dyadobacter, and Cryptococcus and lower abundances of Fusarium, Ralstonia, and Burkholderia. Overall, decreased abundances of F. oxysporum and a lack of variability in the abundance of the biocontrol agent NJN-6 over three years contributed to disease suppression, in combination with alterations in fungal and bacterial composition and abundance, pointing to the sustainability of BIO as an amendment for disease suppression.
•Fusarium wilt disease was pre-controlled by biofertilizer (BIO) in reclaimed field.•Higher bacterial richness and diversity were identified in BIO treated soils.•Bacterial and fungal community composition was altered by BIO treatment.•BIO application significantly reduced the abundance of Fusarium oxysporum.•The inoculum Bacillus amyloliquefaciens NJN-6 exhibited little temporal variation.
Both nitrogen (N) and phosphorus (P) may limit plant production in steppes and affect plant community structure. However, few studies have explored in detail the differences and similarities in the ...responses of belowground microbial communities to long-term N and P inputs. Using a high-throughput Illumina Miseq sequencing platform, we characterized the bacterial communities in a semi-arid steppe subjected to long-term N or P additions. Our results showed that both the Chao richness and Shannon's diversity were negatively correlated to N input rate, while only Chao richness was significantly and negatively correlated to P input rate. Also, both N and P additions altered the bacterial community structure. The bacterial community between plots of the same N or P input rate was much more dissimilar with the higher input level, indicating more severe niche differentiation in pots with higher N or P input. N Inputs significantly increased the relative abundance of the predicted copiotrophic groups (Proteobacteria and Firmicutes) but reduced the predicted oligotrophic groups (Acidobacteria, Nitrospirae, Chloroflexi), with the order Rhizobiales being most affected. P additions significantly affected only two phyla (Armatimonadetes and Chlorobi), which were positively correlated with P source. Results from the structural equation modelling (SEM) showed that N additions affected the bacterial community primarily by changing the pH, while P additions did so mainly by improving P availability. Our results suggest that the below-ground bacterial communities are more sensitive to N inputs, but P inputs can also play an important role in bacterial niche differentiation. These findings improve our understanding of bacterial responses to N and P inputs, and their impacts on bacterial-mediated processes, especially in the context of increasing anthropogenic nutrient inputs.
•Responses of soil bacterial communities to long-term N and P inputs in a steppe were compared.•Both N and P inputs altered the bacterial community but in a different manner.•Severer bacterial community dissimilarity was found by higher N and P inputs.•N inputs affect bacterial community primarily by changing the pH.•P inputs affect the community primarily via mediating P availability.
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