Davide Bulgarelli

Background and aims: Mineral fertilisers are essential for global crop productivity. However, their use is unsustainable due to high energy costs from sourcing and processing, and nitrous oxide emissions after application. An alternative proposition is the use of microalgal biomass as a nutrient source for fertilisation. To date, there is limited data on how the productivity of barley grown with microalgae would compare to barley grown with mineral fertilisers. Furthermore, the impact of the fertiliser source on suitability of grain for malting, one of barley’s main end uses, should be considered. Methods: We quantified the phenology, reflectance indices and yield components of barley cv. Laureate grown with either Chlorella vulgaris powder or mineral fertiliser in three glasshouse trials in different soils, to assess the robustness of our findings under soil-to-soil variation. We extended this to carry out a field trial from which we malted the grain collected at the end of the season and quantified malt quality. Results: We hypothesised that there would be no statistically significant difference in plant performance when grown with microalgae or mineral fertiliser when nitrogen addition was equal. All glasshouse trials and a field trial showed that plants grown with microalgae and mineral fertiliser do not significantly differ in any yield component, yield itself, or measure of malt quality except total malt nitrogen. Conclusions: Supplying the same amount of nitrogen to plants via microalgal biomass instead of mineral fertiliser produced barley with not significantly different yield and selected malt quality indicators as plants grown with mineral fertiliser.

Aims: Root exudates play a central role in rhizosphere processes, many of which support plant growth. While increased exudation under abiotic stresses has been frequently linked to enhanced plant resilience, crop- and genotype- and soil-specific exudation patterns under non-stress conditions remain poorly understood. This study aimed to assess how soil type and genotype influence root exudation in major and emerging European crops and to explore how root morphology and plant growth are related to exudation. Methods: Four genotypes each of barley ( Hordeum vulgare ), faba bean ( Vicia faba ), potato ( Solanum tuberosum ), and sweet potato ( Ipomoea batatas (L.) Lam.) were grown in three distinct European soils under non-stress conditions. Exudates were collected using a soil-hydroponic-hybrid approach and analysed for dissolved organic carbon and nitrogen, as well as total carbohydrates, amino acids, and phenolic compounds. Biomass and root morphology were assessed to examine correlations with exudation patterns. Results: Results showed that soil type and genotype affected exudation patterns, but their influence varied by crop. Plant growth was negatively correlated with exudation rates across most crops, likely reflecting a trade-off in carbon and nitrogen allocation between biomass accumulation and rhizodeposition. Root morphological traits partly correlated with root exudation rates, but no universal relationships were detected across crops. Conclusion: Our results provide novel insights into belowground resource partitioning and broaden the understanding of exudation patterns to previously underexplored crops, highlighting resource allocation trade-offs shaped by genotype and soil as important drivers of exudation dynamics.

Summary: Deciphering the root exudate‐driven interplay between plants and the rhizosphere microbiota is essential for understanding plant adaptation to the environment and future‐proofing crop production. However, sampling root exudates and rhizosphere soil remains challenging due to the low throughput and destructive nature of the process. We used the staple crop barley ( Hordeum vulgare L.) as a model to benchmark different sampling approaches for simultaneous exudation and microbiota profiling of soil‐grown plants. Exudate profiles and total dissolved organic carbon exudation rates were consistent across different sampling approaches, whereas root biomass, root morphology measurements, and organic nitrogen exudation varied. High‐throughput amplicon sequencing and quantitative PCR (qPCR) of phylogenetic markers and nitrogen cycle‐selected genes revealed a protocol‐specific footprint in the composition and abundance of rhizosphere bacterial and fungal microbiota. Yet, on average, 75% of microbes enriched in and differentiating between barley rhizosphere and unplanted soil controls were recovered across all the sampling approaches evaluated. Our results demonstrated that, under the tested conditions, different sampling approaches produced comparable microbiota and exudation patterns, enabling the integrated study of root exudation and microbial profiles from the same plant. The observed differences across sampling approaches must be considered according to the experimental scope.

Tomato is a staple crop and an excellent model to study host-microbiota interactions in the plant food chain. In this study, we describe a “lab-in-the-field” approach to investigate the microbiota of field-grown tomato plants. High-throughput amplicon sequencing revealed a three-microhabitat partition, phyllosphere, rhizosphere, and root interior, differentiating host-associated communities from the environmental microbiota. An individual bacterium, classified as Acinetobacter sp., emerged as a dominant member of the microbiota at the plant-soil continuum. To gain insights into the functional significance of this enrichment, we subjected rhizosphere specimens to shotgun metagenomics. Similar to the amplicon sequencing survey, a “microhabitat effect,” defined by a set of rhizosphere-enriched functions, was identified. Mobilization of mineral nutrients, as well as adaptation to salinity and polymicrobial communities, including antimicrobial resistance genes (ARGs), emerged as a functional requirement sustaining metagenomic diversification. A metagenome-assembled genome representative of Acinetobacter calcoaceticus was retrieved, and metagenomic reads associated with this species identified a functional specialization for plant-growth promotion traits, such as phosphate solubilization, siderophore production, and reactive oxygen species detoxification, which were similarly represented in a tomato genotype-independent fashion. Our results revealed that the enrichment of a beneficial bacterium capable of alleviating plant abiotic stresses appears decoupled from ARGs facilitating microbiota persistence at the root-soil interface. IMPORTANCE: Tomatoes are at center stage in global food security due to their high nutritional value, widespread cultivation, and versatility. Tomatoes provide essential vitamins and minerals, contribute to diverse diets, and support farmer livelihoods, making them a cornerstone of sustainable food systems. Beyond direct dietary benefits, the intricate relationship between tomatoes, their associated microbiota, and antimicrobial resistance gene (ARG) is increasingly recognized. Tomato plants host diverse microbial communities in association with their organs, which influence plant health and productivity. Crop management impacts the composition and function of these communities, contributing to the prevalence of ARGs in the soil and on the plants themselves. These genes can potentially transfer to human pathogens, posing a food safety and public health risk. Understanding these complex interactions is critical for developing sustainable agricultural practices capable of mitigating the impact of climatic modifications and the global threat of antimicrobial resistance.

2025 was a challenging year for the University. Financial restrictions and staff departures meant fewer resources for our public engagement work, and the uncertainty around the University’s future was difficult to face. However, throughout all of this, our staff and students continued to look forward and outwards, sharing their time and enthusiasm with many different audiences across Dundee and beyond – a key effort towards (re-)building University’s reputation. The public engagement team enhanced the training offered around science communication and outreach, and led a very successful programme of training and practice for the UKRI-flagship BARIToNE Collaborative Training Partnership (CTP) at the James Hutton Institute. This culminated in a fun and successful outing at the University’s annual Plant Power day at the Botanic Gardens. We continued engaging with schools and our creative partners, and shared our expertise with other practitioners across the UK. Highlights included: → Over 2000 people engaged with including pupils from 14 local secondary schools and further education colleges, local community groups and people with lived experience of diseases that our scientists study → Over 180 staff and students participated in almost 40 public engagement activities with over a third undertaking more than one event. Participants ranged from undergraduates to Principal Investigators → Over 230 staff and students undertook training from the PE Team including a dedicated programme for BARIToNE PhD students → Over 20 applicants provided with PE Team support for funding with over £40k awarded in 2025 for public engagement related activities from four successful applications → Over 10 documents added to the University of Dundee Research Repository, Discovery in line with our open access approach. Collectively, these documents, which includes how to guides for various activities, reports and resources, were downloaded over 800 times. Looking ahead, we will continue to seek out opportunities to support our engagement work, and maintain the partnerships and projects that we have built. We anticipate the Faculty of Life Sciences will be equally as engaged and inspiring as the School has been and look forward to what is on the horizon. The Life Sciences Public Engagement team

Summary: Deciphering the root exudate-driven interplay between plants and the rhizosphere microbiota is essential for understanding plant adaptation to the environment and future-proofing crop production. However, sampling root exudates and rhizosphere soil remains challenging due to the low throughput and destructive nature of the process. We used the staple crop barley [ Hordeum vulgare ] as a model to benchmark different sampling approaches for simultaneous exudation and microbiota profiling of soil-grown plants. Exudate profiles and total dissolved organic carbon exudation rates were consistent across different sampling approaches, whereas root biomass, root morphology measurements, and organic nitrogen exudation varied. High-throughput amplicon sequencing and quantitative PCR (qPCR) of phylogenetic markers and nitrogen cycle-selected genes revealed a protocol-specific footprint in the composition and abundance of rhizosphere bacterial and fungal microbiota. Yet, on average, 75% of microbes enriched in, and differentiating between, barley rhizosphere and unplanted soil controls were recovered across all the sampling approaches evaluated. Our results demonstrated that, under the tested conditions, different sampling approaches produced comparable microbiota and exudation patterns, enabling the integrated study of root exudation and microbial profiles from the same plant. The observed differences across sampling approaches must be considered according to the experimental scope.

Background and Aims: Mineral fertilisers are essential for global crop productivity. However, their use is unsustainable due to high energy costs from sourcing and processing them, and nitrous oxide emissions after their application. An alternative proposition is the use of microalgal biomass as a nutrient source for fertilisation. To date, there is limited data on how the productivity of barley grown with microalgae would compare to barley grown with mineral fertilisers. Furthermore, the impact of the fertiliser source on suitability of grain for malting, one of barley’s main end uses, should be considered. Methods: We quantified the phenology, reflectance indices and yield components (including yield itself) of barley cv. Laureate grown with either Chlorella vulgaris powder or mineral fertiliser in three glasshouse trials in different soils, to assess the robustness of our findings under soil-to-soil variation. We extended this approach to carry out a field trial from which we malted the grain collected at the end of the season and quantified malt quality. Results: We hypothesised that there would be no statistically significant difference in plant performance when grown with microalgae or mineral fertiliser when nitrogen addition was equal. Both glasshouse trials and a field trial showed that plants grown with microalgae and mineral fertiliser do not significantly differ in any yield component, yield itself, or measure of malt quality except total malt nitrogen. Conclusions: Supplying the same amount of nitrogen to plants via microalgal biomass instead of mineral fertiliser produced barley with the same yield and malt quality as plants grown with mineral fertiliser.

Tomato is a staple crop and an excellent model to study host-microbiota interactions in the plant food chain. In this study we describe a ‘lab-in-the-field’ approach to investigate the microbiota of field-grown tomato plants. High-throughput amplicon sequencing revealed a three-microhabitat partition, phyllosphere, rhizosphere and root interior, differentiating host-associated communities from the environmental microbiota. An individual bacterium, classified as Acinetobacter sp ., emerged as a dominant member of the microbiota at the plant-soil continuum. To gain insights into the functional significance of this enrichment, we subjected rhizosphere specimens to shotgun metagenomics. Similar to the amplicon sequencing survey, a ‘microhabitat effect’ defined by a set of rhizosphere-enriched functions was identified. Mobilisation of mineral nutrients, as well as adaptation to salinity and polymicrobial communities, including antimicrobial resistance genes (ARGs), emerged as a functional requirement sustaining metagenomic diversification. A metagenome-assembled genome (MAG) representative of Acinetobacter calcoaceticus was retrieved and metagenomic reads associated to this species identified a functional specialisation for plant-growth promotion traits (PGPTs), such as phosphate solubilization, siderophores production and reactive oxygen species detoxification, which were similarly represented in across tomato genotype-independent fashion. Our results revealed that the enrichment of a beneficial bacterium capable of alleviating plant’s abiotic stresses appears decoupled from ARGs facilitating microbiota persistence at the root-soil interface. IMPORTANCE: Tomatoes are at centre-stage in global food security due to their high nutritional value, widespread cultivation, and versatility. Tomatoes provide essential vitamins and minerals, contribute to diverse diets, and support farmer livelihoods, making them a cornerstone of sustainable food systems. Beyond direct dietary benefits, the intricate relationship between tomatoes, their associated microbiota, and ARG is increasingly recognised. Tomato plants host diverse microbial communities in association with their organs, which influence plant health and productivity. Crop management impacts on composition and function of these communities, contributing to the prevalence of ARG in the soil and on the plants themselves. These genes can potentially transfer to human pathogens, posing a food safety and public health risk. Understanding these complex interactions is critical for developing sustainable agricultural practices capable of mitigating the impact of climatic modifications and the global threat of antimicrobial resistance.