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The market for seaweed extract biostimulants is experiencing rapid growth, driven by increasing awareness of their benefits and the need for sustainable agricultural practices. This opinion article reviews recent developments in the commercialization of seaweed extract biostimulants, including data on market value and geographical spread, and highlighting the emergence of new species in use. The author advances that recent market trends indicate the start of a gradual transition from wild-harvested to cultivated seaweed sources for biostimulants, while the current proliferation of products is setting the stage for future consolidation of the sector. Challenges to improve market uptake and strategies for companies looking to achieve primacy in the market are discussed.

An increasing need for a more sustainable agriculturally-productive system is required in order to preserve soil fertility and reduce soil biodiversity loss. Microbial biostimulants are innovative technologies able to ensure agricultural yield with high nutritional values, overcoming the negative effects derived from environmental changes. The aim of this review was to provide an overview on the research related to plant growth promoting microorganisms (PGPMs) used alone, in consortium, or in combination with organic matrices such as plant biostimulants (PBs). Moreover, the effectiveness and the role of microbial biostimulants as a biological tool to improve fruit quality and limit soil degradation is discussed. Finally, the increased use of these products requires the achievement of an accurate selection of beneficial microorganisms and consortia, and the ability to prepare for future agriculture challenges. Hence, the implementation of the microorganism positive list provided by EU (2019/1009), is desirable.

Crop production systems have adopted cost-effective, sustainable and environmentally friendly agricultural practices to improve crop yields and the quality of food derived from plants. Approaches such as genetic selection and the creation of varieties displaying favorable traits such as disease and drought resistance have been used in the past and continue to be used. However, the use of biostimulants to promote plant growth has increasingly gained attention, and the market size for biostimulants is estimated to reach USD 4.14 billion by 2025. Plant biostimulants are products obtained from different inorganic or organic substances and microorganisms that can improve plant growth and productivity and abate the negative effects of abiotic stresses. They include materials such as protein hydrolysates, amino acids, humic substances, seaweed extracts and food or industrial waste-derived compounds. Fish processing waste products have potential applications as plant biostimulants. This review gives an overview of plant biostimulants with a focus on fish protein hydrolysates and legislation governing the use of plant biostimulants in agriculture.

The rapidly growing industry of crop biostimulants leverages the application of plant growth promoting rhizobacteria (PGPR) to promote plant growth and health. However, introducing nonnative rhizobacteria may impact other aspects of ecosystem functioning and have legacy effects; these potential consequences are largely unexplored. Nontarget consequences of PGPR may include changes in resident microbiomes, nutrient cycling, pollinator services, functioning of other herbivores, disease suppression, and organic matter persistence. Importantly, we lack knowledge of whether these ecosystem effects may manifest in adjacent ecosystems. The introduced PGPR can leave a functional legacy whether they persist in the community or not. Legacy effects include shifts in resident microbiomes and their temporal dynamics, horizontal transfer of genes from the PGPR to resident taxa, and changes in resident functional groups and interaction networks. Ecosystem functions may be affected by legacies PGPR leave following niche construction, such as when PGPR alter soil pH that in turn alters biogeochemical cycling rates. Here, we highlight new research directions to elucidate how introduced PGPR impact resident microbiomes and ecosystem functions and their capacity for legacy effects.

Abiotic stresses lead to excessive crop yield losses and are a major threat to agriculture. It is essential to equip crops with multi-stress tolerance to mitigate the adverse effects of abiotic stressors and meet the demands of the increasing global population. The association between plants and symbiotic microorganisms is involved in key functions at the ecosystem and plant levels, and the application of microbial plant biostimulants (MPBs) is a sustainable strategy to augment plant growth and productivity, even under abiotic stress conditions. Several different microorganisms can be used as MPBs to enhance plant growth and produce progressive and reproducible effects on crops. In the present review, we assessed the current knowledge on the use of MPBs, discuss the diversity and characteristics of MPBs, and provide a meticulous assessment of the possible applications of MPBs in abiotic stress relief in crops.

Extremophilic environments are rich reservoirs for discovering microorganisms with vast biotechnological potential. Among these, microalgae stand out for their pivotal role in sustainable wastewater treatment and nutrient recycling. This study introduces Coelastrella thermophile D14, a microalga isolated from a solar panel, identified through morphological studies and genomic sequencing. The genus Coelastrella has been characterized and classified as highly productive strains valuable for biofuel and bioproduct generation as well as for their ability to produce significant amounts of carotenoids. Experiments revealed the extraordinary resilience of this strain to prolonged desiccation and high-strength piggery wastewater. Notably, D14 cultivated in 10% pig effluent exhibited biostimulant properties, achieving a germination index 23% higher than the control on Lepidium sativum. In a groundbreaking development, we have successfully established an Agrobacterium-mediated transformation protocol for C. thermophila D14, optimizing key parameters for effective T-DNA transfer. This marks a pioneering achievement within the genus Coelastrella. These findings highlight the significant potential of D14 as a robust platform for future biotechnological applications, opening new opportunities for innovative solutions, especially in environmental protection and sustainable agriculture.Key points center dot First microalga from solar panel biofilm: Coelastrella sp. D14 isolated and characterized.center dot Strain D14 tolerates prolonged desiccation and grows well in piggery wastewater.center dot Stable Agrobacterium-mediated transformation enables future metabolic engineering.Key points center dot First microalga from solar panel biofilm: Coelastrella sp. D14 isolated and characterized.center dot Strain D14 tolerates prolonged desiccation and grows well in piggery wastewater.center dot Stable Agrobacterium-mediated transformation enables future metabolic engineering.Key points center dot First microalga from solar panel biofilm: Coelastrella sp. D14 isolated and characterized.center dot Strain D14 tolerates prolonged desiccation and grows well in piggery wastewater.center dot Stable Agrobacterium-mediated transformation enables future metabolic engineering.

Microalgae are increasingly recognized as a valuable resource for bolstering sustainability in agriculture. However, current research and patents primarily focus on Chlorella spp., Scenedesmus spp., and Spirulina spp., thus leaving the vast diversity of microalgae relatively unexplored for agricultural applications. Euglena gracilis (Euglenophyta) is a microalga renowned for its resilience to diverse environmental stressors and capability to produce a variety of bioactive metabolites. This study investigated the potential of cultivating E. gracilis in piggery wastewater for nutrient recycling and as a source of beneficial biomolecules, particularly for biostimulant use. Utilizing raw wastewater diluted to 25% (P25) and pre-treated wastewater with photo-Fenton (PF), the research found that E. gracilis exhibited elevated cell density, biomass concentration, and overall cell health in both wastewaters compared to a synthetic medium (BG11-NPK). This was due to its efficient removal of nutrients, especially ammoniacal-nitrogen and phosphate, resulting in a biomass rich in polyunsaturated fatty acids, amino acids, and paramylon content. The whole-cell biomass significantly enhanced the germination index of lettuce and tomato seeds compared to the water control. Additionally, it promoted cell expansion and root formation in cucumber cotyledons, exhibiting similarities to phytohormones such as gibberellin, cytokinin, and auxin. Furthermore, it is suggested that E. gracilis biomass contains molecules related to resistance to environmental stresses, particularly in tomatoes, given the enhancement in the seedling vigor index. E. gracilis exhibited remarkable adaptability to piggery wastewater, recycling nutrients and yielding biomass rich in bioactive molecules with potential as plant biostimulants. These findings significantly contribute to understanding E. gracilis's potential applications in agriculture and developing a circular bioeconomy.

Microalgal exopolysaccharides represent a potential sustainable alternative for the enhancement and protection of agricultural crops including management of both biotic and abiotic stress. In the present study, we investigated the potential of Dunaliella salina exopolysaccharides (PS) to attenuate the effect of salt stress on growth of Solanum lycopersicum, which was grown under different salinity levels (3 and 6 g L−1 NaCl). The effects of PS treatment on plant growth, osmoprotectant molecules, protein content, and antioxidant enzymes activities of tomato plants under salt stress were analyzed. A metabolomics study showed that the exopolysaccharides released by D. salina contained sulfated moiety along with carbohydrates and uronic acids. The application of sulfated exopolysaccharides on tomato plants alleviated the salt stress and mitigated the decrease in length and dry weight of the plant’s shoot and root systems, as well as that of potassium (K+), and K+/Na+ ratio. Furthermore, the increase in proline, phenolic compounds, Na+, and antioxidant enzymes (CAT, POD, SOD) activities caused by salt stress were attenuated after the exopolysaccharide treatment. GC-MS metabolomics analysis showed that PS treatment allowed the activation and/or inhibition of various metabolic pathways involved in the plant’s tolerance to stress such as jasmonic acid-dependent pathways. This study shows the potential of microalgal exopolysaccharides for enhancing tomato tolerance to salt stress and highlights the possibility of their use as plant growth biostimulants under harsh environmental conditions.

Tomato (Solanum lycopersicum L.) is among the most important horticultural crops globally, and interest in improving both yield and quality through sustainable strategies is increasing. This study assessed the effects of a biostimulant based on humic acids and microorganisms on the yield and organoleptic quality of two saladette tomato varieties (Macizo and Moctezuma) under greenhouse conditions. A randomized complete block design with four replicates compared control treatments (CT) without biostimulant to biostimulant treatments (BT). Biostimulant application significantly increased yield in both varieties (p<0.05), with Macizo rising from 27 to 37.5 kg/plant (39%) and Moctezuma from 28.5 to 42 kg/plant (47%). Quality improvements included greater equatorial diameter in Moctezuma and increased firmness in Macizo (p<0.05). After 14 days at 19 °C, BT fruits lost significantly less weight than CT fruits. Flavonoid content increased in BT (Macizo: 4.46 vs 1.48 mg QE/100 g; Moctezuma: 3.36 vs 1.25 mg QE/100 g), while antioxidant activity and total phenolics decreased (p<0.05). No differences were found in color, soluble solids, or titratable acidity (p>0.05). These results indicate that biostimulants can enhance tomato yield and some quality traits, but their influence on secondary metabolites may differ depending on variety and cultivation conditions.

Melatonin is a ubiquitous indolamine, largely investigated for its key role in the regulation of several physiological processes in both animals and plants. In the last century, it was reported that this molecule may be produced in high concentrations by several species belonging to the plant kingdom and stored in specialized tissues. In this review, the main information related to the chemistry of melatonin and its metabolism has been summarized. Furthermore, the biosynthetic pathway characteristics of animal and plant cells have been compared, and the main differences between the two systems highlighted. Additionally, in order to investigate the distribution of this indolamine in the plant kingdom, distribution cluster analysis was performed using a database composed by 47 previously published articles reporting the content of melatonin in different plant families, species and tissues. Finally, the potential pharmacological and biostimulant benefits derived from the administration of exogenous melatonin on animals or plants via the intake of dietary supplements or the application of biostimulant formulation have been largely discussed.