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The exponential growth of the greenhouse industry in recent years has led to an increasing demand for economic, “green”, soilless substrates and soilless substrate amendments. To meet this demand, many growers have begun incorporating wood fibers (WFs) into their production systems because they are both economic and renewable. WF’s rise in popularity has motivated an uptick in research focused on understanding how WF amendments affect substrate physical and chemical properties, and how these changes influence plant health, soil-borne disease trends, and microbiome dynamics.Wood fibers have been reported to suppress damping-off of radish caused by Rhizoctonia solani, however, the scope of the effectiveness of wood fiber-based disease suppression, and the mode of action of this suppression, remains unknown. Wood fibers contain large amounts of the carbon-rich sugars, hemicellulose and cellulose, which are readily metabolized by a multitude of microbial community member species in soilless substrates, likely resulting in changes to community diversity and composition. Indeed, research has shown that substrates amended with pine WFs have significantly higher fungal diversity than peat substrates. The natural disease suppression of WF-amended substrates could be partially due to an increase in microbial diversity that hinders pathogen infection. However, it is unclear whether the reported changes in microbiome composition will be observed under greenhouse production conditions or if they are affected by WF processing method.This study aimed to address these knowledge gaps by conducting a series of greenhouse trials. The first objective was to evaluate the effects of different WF-processing methods on suppression of disease caused by Pythium ultimum -- a common greenhouse pathogen whose biology and life cycle are both distinctly different from Rhizoctonia solani. The second objective was to evaluate if microbiome composition in WF-amended substrates reflected potential microbial links to disease suppressive ability. To this end, a greenhouse bioassay for Pythium root rot of chrysanthemum was developed, assessed for disease suppression, and sampled for bacterial 16s rRNA gene amplification and community analysis.In designing the bioassay, 4 Pythium isolates were evaluated for pathogenicity in cucumbers in the growth chamber. Cucumber was chosen due to its susceptibility to Pythium damping-off and its suitability as a high-throughput model organism. Results from the cucumber trials indicated two strains from our available set of four that were more effective at causing disease in cucumber when applied as a potato soil inoculum. To then establish pathogenicity in chrysanthemum, both isolates were evaluated at three different dosage levels in a bioassay conducted in the greenhouse. These initial chrysanthemum trials informed best practices for cutting age at the time of inoculation, dosage level, and pathogen choice in the final chrysanthemum bioassay.Using the optimized chrysanthemum bioassay methods, the disease suppression capabilities of three WF-amended substrates against Pythium root rot were evaluated and compared to a grower standard mixture of Sphagnum-peat:perlite. The three pine WF-amendments used in this study were process using either twin-disc refinement, screw-extrusion, or hammer-milling methods. Plants used for these trials were also sampled for 16s rRNA gene sequencing and analysis. The alpha diversity of the bacterial communities of the WF-amended substrates under both inoculated and non-inoculated conditions were then compared to grower standard controls. A reduction in the disease severity of plants grown in hammermilled and extruded WFs was observed. No differences in bacterial alpha-diversity were found between WF types, or between WF and control substrates under any level of inoculation. However, there was a difference in diversity between initial (freshly mixed, not yet used to fill trial pots) WF-substrates and the peat control. Initial WF-substrates all had significantly lower Shannon entropy scores than the control but were not different from each other.The results from this study suggest that there is an effect of WF-processing method on suppressiveness. A buffer effect against Pythium root rot was only afforded to chrysanthemums grown in hammermilled or extruded WF varieties. This research expanded industry professionals' understanding of the effectiveness of WF substrates as a disease management technique and provided essential information to help growers make informed purchasing decisions as they continue to integrate WF-amended substrates into their operations.

For this study, 340 children <18 months old from a low-income, urban neighborhood in Cali, Colombia, were observed from birth by means of weekly home visits to detect cases of acute respiratory tract infection. All suspected cases were confirmed by trained doctors in a special clinic. Information on symptoms, signs, and potential risk factors was documented prospectively. Etiologic agents were identified in cases of lower respiratory tract infection (LRI). The overall incidence of upper respiratory tract infection was 6.6 cases per child-year at risk. The incidence of upper respiratory tract infection was 4.9 cases per child-year at risk and that of LRI was 1.7 cases per child-year at risk. Crowding in the home was found to be significantly associated with an increased incidence of LRI. Respiratory syncytial virus was the viral agent most frequently isolated from cultures of nasopharyngeal aspirates of children with LRI. Staphylococcus aureus was the bacterial agent most frequently isolated from the blood of patients with LRI.

Plant resistance to heat stress can be modelled by variation attributable to the genotype, environment, the rhizosphere microbiome, and their interactions. Using this Genotype × Environment × Rhizosphere Microbiome (GERMs) model, we studied three cereal genotypes: two inbred maize lines with contrasting heat sensitivity, and a sorghum inbred that displayed moderate heat tolerance. Plants were grown under optimal and heat stressed conditions across two soil treatments. We developed a systems-level metatranscriptomics approach to examine both plant and microbial transcriptomic profiles and integrated them with microbiome compositional data and plant phenotypes. We compared our strategy to amplicon profiling and found that our metatranscriptomic strategy offers greater functional and taxonomic resolution, allowing us to characterize active microbial pathways and analyze them jointly with plant gene expression profiles within a single system. We show that the microbiome functional profile is driven by host genotype and environmental factors and can enhance plant resilience. Our analyses identified plant genes and microbial pathways consistently associated with heat tolerance and key host-microbe interactions. Specifically, we identified D-amino acid metabolism as a plausible mechanism underlying a synergistic response to heat stress. These results demonstrate that the rhizosphere microbiome is not a passive component but an active participant in plant responses to abiotic stress. This work offers a new perspective on cereal adaptation to high temperatures and underscores the utility of the GERMs framework for dissecting functional relationships among plant genotype, environment, and the rhizosphere microbiome.