A Microbial Fermentation Product Induces Defense-Related Transcriptional Changes and the Accumulation of Phenolic Compounds in Glycine max.

With the progressive loss of fungicide efficacy against Phakopsora pachyrhizi, the causal agent of Asian soybean rust (ASR), alternative methods to protect soybean crops are needed. Resistance induction is a low impact alternative and/or supplement to fungicide applications that fortifies innate plant defenses against pathogens. Here, we show that a microbial fermentation product (MFP) induces plant defenses in soybean, and transcriptional induction is enhanced with the introduction of ASR. MFP-treated plants exhibited 1,011 and 1,877 differentially expressed genes (DEGs) 12 and 60 h after treatment, respectively, compared with water controls. MFP plants exposed to the pathogen 48 h after application and sampled 12 h later (for a total of 60 h) had 2,401 DEGs compared with control. The plant defense genes PR1, PR2, IPER, PAL, and CHS were induced with MFP application, and induction was enhanced with ASR. Enriched pathways associated with pathogen defense included plant-pathogen interactions, MAPK signaling pathways, phenylpropanoid biosynthesis, glutathione metabolism, flavonoid metabolism, and isoflavonoid metabolism. In field conditions, elevated antioxidant peroxidase activities and phenolic accumulation were measured with MFP treatment; however, improved ASR control or enhanced crop yield were not observed. MFP elicitation differences between field and laboratory grown plants necessitates further testing to identify best practices for effective disease management with MFP-treated soybean.

Effect of green waste and lime amendments on biostabilisation, physical-chemical and microbial properties of the composted fine fraction of residual municipal solid waste.

Implementation of guidelines to reduce the amount of biodegradable municipal waste (BMW) sent to landfill has created a need in the waste-management industry to investigate possible methods of accelerating biostabilisation of residual BMW. The effect of commercially feasible manipulations (lime and green waste (GW)) on the rate of biostabilisation of the fine (<20 mm) fraction of residual BMW was investigated. The physical and chemical attributes of the composted wastes were measured, and their bacterial communities profiled using traditional culture-based methods. In addition, ammonia-oxidising microbes were monitored during the biostabilisation process using molecular profiling methods. Addition of GW accelerated biostabilisation, reduced conductivity and increased the levels of ammonia-oxidising bacterial (AOB) and archaeal (AOA) genes. The best stability was noted in the dual (Lime + GW) treatment, which was under the limit of 13 mmol O2 kg DM-1 h-1 recommended by the Irish compost standard. Biostabilised wastes met recommendations for source-segregated compost for pH (6-8) and pathogens (E. coli and Salmonella), but not heavy metals, indicating their unsuitability for uses other than landfill cover. Levels of AOA genes (log 3-6 g-1 DM) were higher than AOB (log 1-6 g-1 DM, indicating AOA may contribute more to potential ammonia oxidation in residual BMW composting.

Transcriptomic Response of Huanglongbing-Infected Citrus sinensis Following Field Application of a Microbial Fermentation Product.

Huanglongbing (HLB) is considered the most destructive disease in Citrus production and threatens the future of the industry. Microbial-derived defense elicitors have gained recognition for their role in plant defense priming. This work assessed a 5% (V/V) microbial fermentation application (MFA) and its role in the elicitation of defense responses in HLB-infected Citrus sinensis trees following a foliar application with a pump sprayer. Using a PCR detection method, HLB infection levels were monitored in healthy and infected trees for 20months. Nutrient analysis assessed N, P, K, Ca, Mg, Mn, Zn, Fe, B, and Cu concentrations in the trees. MFA significantly increased Cu concentrations in treated trees and resulted in the stabilization of disease index (DI) in infected trees. Initial real-time qPCR analysis of defense-associated genes showed a significant increase in pathogenesis-related protein 2 (PR2) and phenylalanine ammonia lyase (PAL) gene expression in healthy and HLB-infected trees in response to MFA. Gene expression of PR2 and PAL peaked 6h post-microbial fermentation application during an 8-h sampling period. A transcriptomic assessment using GeneChip microarray of the hour 6 samples revealed differential expression of 565 genes when MFA was applied to healthy trees and 909 genes when applied infected citrus trees when compared to their respective controls. There were 403 uniquely differentially expressed genes in response to MFA following an intersectional analysis of both healthy and infected citrus trees. The transcriptomic analysis revealed that several genes associated with plant development, growth, and defense were upregulated in response to MFA, including multiple PR genes, lignin formation genes, ROS-related genes, hormone synthases, and hormone regulators. This study provides further evidence that MFA may play an important role as a plant elicitor in an integrated pest management strategy in citrus and other agronomically important crops.

Re-addressing the biosafety issues of plant growth promoting rhizobacteria.

To promote agronomic sustainability, extensive research is being carried out globally, investigating biofertilizer development. Recently, it has been realized that some microorganisms used as biofertilizers behave as opportunistic pathogens and belong to the biosafety level 2 (BSL-2) classification. This poses serious risk to the environmental and human health. Evidence presented in various scientific forums is increasingly favoring the merits of using BSL-2 microorganisms as biofertilizers. In this review, we emphasize that partial characterization based on traditional microbiological approaches and small subunit rRNA gene sequences/conserved regions are insufficient for the characterization of biofertilizer strains. It is advised herein, that research and industrial laboratories developing biofertilizers for commercialization or environmental release must characterize microorganisms of interest using a multilateral polyphasic approach of microbial systematics. This will determine their risk group and biosafety characteristics before proceeding with formulation development and environmental application. It has also been suggested that microorganisms belonging to risk-group-1 and BSL-1 category should be used for formulation development and for field scale applications. While, BSL-2 microorganisms should be restricted for research using containment practices compliant with strict regulations.

Application of Endophytic Pseudomonas fluorescens and a Bacterial Consortium to Brassica napus Can Increase Plant Height and Biomass under Greenhouse and Field Conditions.

Plant associated bacteria with plant growth promotion (PGP) properties have been proposed for use as environmentally friendly biofertilizers for sustainable agriculture; however, analysis of their efficacy in the field is often limited. In this study, greenhouse and field trials were carried out using individual endophytic Pseudomonas fluorescens strains, the well characterized rhizospheric P. fluorescens F113 and an endophytic microbial consortium of 10 different strains. These bacteria had been previously characterized with respect to their PGP properties in vitro and had been shown to harbor a range of traits associated with PGP including siderophore production, 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase activity, and inorganic phosphate solubilization. In greenhouse experiments individual strains tagged with gfp and Kmr were applied to Brassica napus as a seed coat and were shown to effectively colonize the rhizosphere and root of B. napus and in addition they demonstrated a significant increase in plant biomass compared with the non-inoculated control. In the field experiment, the bacteria (individual and consortium) were spray inoculated to winter oilseed rape B. napus var. Compass which was grown under standard North Western European agronomic conditions. Analysis of the data provides evidence that the application of the live bacterial biofertilizers can enhance aspects of crop development in B. napus at field scale. The field data demonstrated statistically significant increases in crop height, stem/leaf, and pod biomass, particularly, in the case of the consortium inoculated treatment. However, although seed and oil yield were increased in the field in response to inoculation, these data were not statistically significant under the experimental conditions tested. Future field trials will investigate the effectiveness of the inoculants under different agronomic conditions.

Draft Genome Sequence of Three Endophyte Strains of Pseudomonas fluorescens Isolated from Miscanthus giganteus.

We report here the draft genome sequence of three Pseudomonas fluorescens strains (L111, L228, and L321) isolated from Miscanthus giganteus The draft genome analyses uncovered a group of genes involved in the biosynthesis of secondary metabolites and for plant growth promotion.

Plant growth promotion induced by phosphate solubilizing endophytic Pseudomonas isolates.

The use of plant growth promoting bacterial inoculants as live microbial biofertilizers provides a promising alternative to chemical fertilizers and pesticides. Inorganic phosphate solubilization is one of the major mechanisms of plant growth promotion by plant associated bacteria. This involves bacteria releasing organic acids into the soil which solubilize the phosphate complexes converting them into ortho-phosphate which is available for plant up-take and utilization. The study presented here describes the ability of endophytic bacteria to produce gluconic acid (GA), solubilize insoluble phosphate, and stimulate the growth of Pisum sativum L. plants. This study also describes the genetic systems within three of these endophyte strains thought to be responsible for their effective phosphate solubilizing abilities. The results showed that many of the endophytic strains produced GA (14-169 mM) and have moderate to high phosphate solubilization capacities (~400-1300 mg L(-1)). When inoculated into P. sativum L. plants grown in soil under soluble phosphate limiting conditions, the endophytes that produced medium-high levels of GA displayed beneficial plant growth promotion effects.

Ecopiling: a combined phytoremediation and passive biopiling system for remediating hydrocarbon impacted soils at field scale.

Biopiling is an ex situ bioremediation technology that has been extensively used for remediating a wide range of petrochemical contaminants in soils. Biopiling involves the assembling of contaminated soils into piles and stimulating the biodegrading activity of microbial populations by creating near optimum growth conditions. Phytoremediation is another very successful bioremediation technique and involves the use of plants and their associated microbiomes to degrade, sequester or bio-accumulate pollutants from contaminated soil and water. The objective of this study was to investigate the effectiveness of a combined phytoremediation/biopiling system, termed Ecopiling, to remediate hydrocarbon impacted industrial soil. The large scale project was carried out on a sandy loam, petroleum impacted soil [1613 mg total petroleum hydrocarbons (TPHs) kg(-1) soil]. The contaminated soil was amended with chemical fertilizers, inoculated with TPH degrading bacterial consortia and then used to construct passive biopiles. Finally, a phyto-cap of perennial rye grass (Lolium perenne) and white clover (Trifolium repens) was sown on the soil surface to complete the Ecopile. Monitoring of important physico-chemical parameters was carried out at regular intervals throughout the trial. Two years after construction the TPH levels in the petroleum impacted Ecopiles were below detectable limits in all but one subsample (152 mg TPH kg(-1) soil). The Ecopile system is a multi-factorial bioremediation process involving bio-stimulation, bio-augmentation and phytoremediation. One of the key advantages to this system is the reduced costs of the remediation process, as once constructed, there is little additional cost in terms of labor and maintenance (although the longer process time may incur additional monitoring costs). The other major advantage is that many ecological functions are rapidly restored to the site and the process is esthetically pleasing.