Wendy A. Stirk
7003732038
Publications - 12
Microalgal and cyanobacterial biostimulants used in wheat and maize production
Publication Name: Biostimulants for Improving Reproductive Growth and Crop Yield
Publication Date: 2025-01-01
Volume: Unknown
Issue: Unknown
Page Range: 169-218
Description:
Wheat and maize are staple cereals that are each cultivated on about 200 million hectares globally. Microalgae and cyanobacteria have potential to be developed as biostimulants for wheat and maize production. This review focuses on biostimulating effects of various microalgae and cyanobacteria on seed priming, soil and foliar treatments applied in pot experiments and field trials. Two case studies on wheat and maize field trials are included. Seed priming with selected microalgal extracts is a promising method to promote plant growth but still needs validation in field trials. Soil biofertilizers based on living N2-fixing cyanobacteria (algalization) applied alone or in combination with plant growth promoting rhizobacteria modulate soil microbial composition and enhance nutrient uptake. However, this requires application of tens or hundreds kg/ha biomass to substitute for N-fertilizers so is not yet an economically viable option. The case studies indicated that a single foliar treatment of wheat at tillering and maize at the V6 growth stage with Chlorella vulgaris or Tetracystis sp. suspensions (0.1–1g DW/L applied at 400L/ha) increased grain yield, grain protein content and improve stress tolerance. These results indicated that certain microalgae could be effective biostimulants. However, producing sufficient microalgae biomass on a commercial scale is still a challenge. Monoalgal mass production in closed photobioreactors is expensive. A promising approach is the cultivation of mixed algal cultures in nutrient rich wastewater using open raceway reactors.
Open Access: Yes
Cyanobacteria-Fungi Co-Cultures: Which Partner Contributes to Antifungal Activity?
Publication Name: Current Microbiology
Publication Date: 2024-11-01
Volume: 81
Issue: 11
Page Range: Unknown
Description:
Cyanobacteria synthesize secondary metabolites with antifungal activity, making them potential biopesticide agents for sustainable, eco-friendly agriculture. Programmes to identify Cyanobacterial strains with effective bioactivity generally screen strains maintained in culture collections. These strains are often monoclonal but non-axenic and this may potentially influence the bioactivity of the generated biomass. The present study investigated in vitro antifungal activity of Nostoc muscorum MACC-189 and N. linckia MACC-612 strains co-isolated with fungal co-partners and maintained in the Mosonmagyaróvár Algal Culture Collection (MACC). The fungal co-partners were isolated from the Cyanobacterial stock cultures and identified as Purpureocillium lilacinum and Sarocladium sp., respectively. The cultures were tested against seven phytopathogens. The phytopathogenic fungi were grown on potato dextrose agar plates and suspension cultures of the Cyanobacteria-fungi and isolated fungal co-partners were placed in the centre of the plate. Antifungal effects were assessed semi-quantitatively after 10 days of incubation. The Cyanobacteria-fungal co-cultures had antifungal activity against Monilinia fructigena and Aspergillus sp. with the N. muscorum/P. lilacinum culture being the most effective. The fungal isolates inhibited M. fructigena with P. lilacinum having a dose-dependent response but did not inhibit Aspergillus sp. This suggested that the antifungal effect of the Cyanobacterial cultures on M. fructigena was due to the fungal partner rather than the cyanobacterium while the antifungal effect on Aspergillus sp. was due to the cyanobacterium partner. As it was not possible to maintain living axenic N. muscorum and N. linckia cultures, this could not be conclusively confirmed. These results highlight the importance of either using axenic cultures or identifying the co-isolates when testing Cyanobacteria cultures for antifungal bioactivity.
Open Access: Yes
Comparison of plant biostimulating properties of Chlorella sorokiniana biomass produced in batch and semi-continuous systems supplemented with pig manure or acetate
Publication Name: Journal of Biotechnology
Publication Date: 2024-02-10
Volume: 381
Issue: Unknown
Page Range: 27-35
Description:
Microalgae-derived biostimulants provide an eco-friendly biotechnology for improving crop productivity. The strategy of circular economy includes reducing biomass production costs of new and robust microalgae strains grown in nutrient-rich wastewater and mixotrophic culture where media is enriched with organic carbon. In this study, Chlorella sorokiniana was grown in 100 l bioreactors under sub-optimal conditions in a greenhouse. A combination of batch and semi-continuous cultivation was used to investigate the growth, plant hormone and biostimulating effect of biomass grown in diluted pig manure and in nutrient medium supplemented with Na-acetate. C. sorokiniana tolerated the low light (sum of PAR 0.99 ± 0.18 mol/photons/(m2/day)) and temperature (3.7–23.7° C) conditions to maintain a positive growth rate and daily biomass productivity (up to 149 mg/l/day and 69 mg/l/day dry matter production in pig manure and Na-acetate supplemented cultures respectively). The protein and lipid content was significantly higher in the biomass generated in batch culture and dilute pig manure (1.4x higher protein and 2x higher lipid) compared to the Na-acetate enriched culture. Auxins indole-3-acetic acid (IAA) and 2-oxindole-3-acetic acid (oxIAA) and salicylic acid (SA) were present in the biomass with significantly higher auxin content in the biomass generated using pig manure (> 350 pmol/g DW IAA and > 84 pmol/g DW oxIAA) compared to cultures enriched with Na-acetate and batch cultures (< 200 pmol/g DW IAA and < 27 pmol/g DW oxIAA). No abscisic acid and jasmonates were detected. All samples had plant biostimulating activity measured in the mungbean rooting bioassay with the Na-acetate supplemented biomass eliciting higher rooting activity (equivalent to 1–2 mg/l IBA) compared to the pig manure (equivalent to 0.5–1 mg/l IBA) and batch culture (equivalent to water control) generated biomass. Thus C. sorokiniana MACC-728 is a robust new strain for biotechnology, tolerating low light and temperature conditions. The strain can adapt to alternative nutrient (pig manure) and carbon (acetate) sources with the generated biomass having a high auxin concentration and plant biostimulating activity detected with the mungbean rooting bioassay.
Open Access: Yes
Cataloguing microalgae and Cyanobacteria strains from the Mosonmagyaróvár Algal Culture Collection with in vitro antagonistic activity against phytopathogenic fungi and oomycetes
Publication Name: Phytoparasitica
Publication Date: 2023-09-01
Volume: 51
Issue: 4
Page Range: 747-762
Description:
Microalgae produce many secondary metabolites that are biologically active, including compounds that inhibit microbial growth. These could potentially function as biofungicides. The first selection criteria for potential strains suitable in the phytosanitary market is good in vitro inhibition of growth against specific phytopathogenic fungi and oomycetes and higher biomass productivity rates. In the present study, water extracts were prepared from 280 strains comprising of 33 Cyanophyceae strains (13 genera), 157 Chlorophyceae strains (29 genera), 80 Trebouxiophyceae strains (19 genera), 5 Klebsormidiophyceae strains (1 genus) and 1 Zygnematophyceae strain. These were tested in vitro against 6 phytopathogenic fungi and 3 phytopathogenic oomycetes. In total, 45% of the species had mycelial growth inhibitory activity against at least one pathogen. Cyanobacteria had the highest “hit-rate” (64%), followed by the Chlorophyceae (49%) and Trebouxiophyceae (30%). Water extracts of 19 strains had fungicidal and/or oomyceticidal activity – these were predominantly Cyanobacteria. The Cyanobacteria displayed a wider spectrum of inhibition with five strains being active against three or more phytopathogenic strains. Trichormis variabilis MACC-304 and Tolypothrix tenuis MACC-205 had inhibitory activity against 6 phytopathogens and Nostoc linckia MACC-612 inhibited 4 phytopathogenic strains. Each Chlorophyta strain was only active against 1-2 strains. However, the daily productivity rates of Cyanobacteria were significantly lower than Chlorophyta strains. Further investigation of 15 Nostocales species (Nostocaceae, Tolypothrichaceae and Calotrichaceae) showed the Nostoc species generally had significantly lower biomass generation compared to other Nostocacaeae strains. The most promising strain was Tolypothrix tenuis MACC-205 which had the most potent, broad spectrum fungal and oomyceticidal inhibitory activity as well as significantly higher daily biomass productivity rates. Thus, Cyanobacteria can potentially be developed as an effective agricultural tool for environmentally-friendly disease management.
Open Access: Yes
Effect of storage on plant biostimulant and bioactive properties of freeze-dried Chlorella vulgaris biomass
Publication Name: Journal of Applied Phycology
Publication Date: 2021-12-01
Volume: 33
Issue: 6
Page Range: 3797-3806
Description:
Microalgae are potential plant biostimulants and biocontrol agents. A major hurdle towards their commercialization is the production of large volumes of biomass at the correct time of year. Secondary metabolites are unstable and the “shelf-life” of bioactive microalgal biomass needs to be investigated. The aim of the study was to investigate the effects of storage conditions on freeze-dried microalgae to determine how long the biomass retained its growth promoting and bioactive properties under various temperature and light conditions. Chlorella vulgaris biomass was stored in the dark at − 70 °C, 10 °C, and 25 °C and in the light at 25 °C. Samples were tested every 3–4 months for 15 months. Storage time significantly influenced the rate of change in the bioactivity in the C. vulgaris biomass with storage temperature also having some effect. Rooting activity decreased in the mungbean rooting assay over time up to 12 months and then increased slightly. Antimicrobial activity increased against Staphylococcus aureus and Escherichia coli for up to 12 months and then declined. Antioxidant activity measured in the DPPH assay remained relatively stable for up to 12 months and then significantly decreased with longer storage. The change in bioactivity over time was attributed to the gradual breakdown of the rigid cell wall of C. vulgaris, thereby improving extraction efficiency but exposing the secondary metabolites to oxygen, thus quickening their degradation. Biomass produced for commercial purposes requires preliminary validation as the results of the present study showed that bioactive compounds are susceptible to degradation over time.
Open Access: Yes
Comparison of monocultures and a mixed culture of three Chlorellaceae strains to optimize biomass production and biochemical content in microalgae grown in a greenhouse
Publication Name: Journal of Applied Phycology
Publication Date: 2021-10-01
Volume: 33
Issue: 5
Page Range: 2755-2766
Description:
Light and temperature are important environmental conditions affecting microalgal growth in outdoor culture. It is essential to evaluate microalgae strains growing under outdoor conditions where they are subjected to variable environmental parameters. The present study investigated three Chlorellaceae strains (Micractinium sp. MACC-728, Chlorella sorokiniana MACC-438, and C. sorokiniana MACC-452) and a mixed culture combining these three strains. Cultures were grown in 2-L bioreactors in a greenhouse over 3 months to assess the effects of high temperature and light on their growth, macromolecule content, and antioxidant and plant-stimulating bioactivities. The most influential environmental parameters on growth were average air temperature and the sum of photosynthetically active radiation, followed by maximum air temperature. The most affected growth parameter was daily change in cell number. Chlorella sorokiniana MACC-438 produced the lowest biomass and was most affected by the high temperature and light conditions. Micractinium sp. produced the highest biomass and was least affected, suggesting it was the most suitable strain for outdoor cultivation. The mixed Chlorellaceae culture performed well in biomass production, exceeding C. sorokiniana monocultures but significantly underyielding in lipid content. Antioxidant activity and the root-stimulating activity varied with strain and culture age. Micractinium sp. had the highest but most variable antioxidant and plant-stimulating activity. Bioactivity in the mixed culture was more consistent, remaining high regardless of culture age and environmental conditions. Thus, mixed cultures of productive strains could be a useful strategy to ensure stable and high-quality biomass production in outdoor cultivation with fluctuating environmental conditions.
Open Access: Yes
Plant biostimulating effects of the cyanobacterium Nostoc piscinale on maize (Zea mays L.) in field experiments
Publication Name: South African Journal of Botany
Publication Date: 2021-08-01
Volume: 140
Issue: Unknown
Page Range: 153-160
Description:
Biostimulants, when applied to plants in small amounts, increase crop yield and plant tolerance to abiotic and biotic stress. They play an important role in the development of new environmentally sustainable technologies. The aim of the current experiment was to investigate the potential of a cyanobacterium strain (Nostoc piscinale) to improve the growth, grain yield and stress tolerance of maize (Zea mays SY Zephir hybrid). Field trials were established at two sites. Freeze-dried biomass of N. piscinale resuspended in tap water (1g/L DW) was applied as a single foliar treatment (400 L/ha) at the V6-V7 phenological stage. Number of leaves, chlorophyll content, relative water content (RWC%) and free proline content were measured weekly. Grain yield, yield components and grain protein content were measured at harvest. N. piscinale treated maize had significantly earlier development in the vegetative growth stages with a higher number of leaves. Chlorophyll content (SPAD value) was significantly higher in the treated plants during the reproductive stages. There was little difference in the RWC and proline content compared to control plants. Faster vegetative growth and higher chlorophyll content in the cyanobacterium treated plants meant great photosynthetic light absorption over a longer period of time, resulting in significantly higher grain yield (6.5% and 11.5% at the two production sites) and increased grain protein content. Grain yield was significantly influenced by cob length and thousand grain weight. In conclusion, it was proved in field trials conducted in two different regions in Hungary that a single foliar application of a cyanobacterium-based biostimulant can contribute to crop production in a sustainable and environmentally friendly manner.
Open Access: Yes
Categories of various plant biostimulants - Mode of application and shelf-life
Publication Name: Biostimulants for Crops from Seed Germination to Plant Development A Practical Approach
Publication Date: 2021-01-01
Volume: Unknown
Issue: Unknown
Page Range: 1-60
Description:
A plant biostimulant is any substance or microorganism which can be applied to plants to enhance seed germination and plant growth development along with its nutritional efficiency. Plant biostimulants collectively influence: plant growth development, pollen tube development, flower and fruit set, plant pigments, shoot and root development, nutritional efficiency, yield and shelf-life of crops, rhizospheric and soil microorganisms, general soil health and plant-environment interactions. Biostimulants are derived from natural origins and can help reduce the use of chemical products and also mitigate the negative impacts of harmful chemicals in the environment. This chapter focuses on their modes of application and effects on crops and horticultural plants. It also emphasizes impacts on the shelf-life and efficiencies of commercial biostimulants, as compared to synthetic chemical products and highlights the opportunities and challenges of their market expansion.
Open Access: Yes
Effect of cell disruption methods on the extraction of bioactive metabolites from microalgal biomass
Publication Name: Journal of Biotechnology
Publication Date: 2020-01-10
Volume: 307
Issue: Unknown
Page Range: 35-43
Description:
Microalgae synthesize a variety of potentially high-value compounds. Due to their robust cell wall, cell disruption is necessary to improve extraction of these compounds. While cell disruption methods have been optimized for lipid and protein extraction, there are limited studies for other bioactive compounds. The present study investigated the effect of freeze-drying combined with sonication or ball-milling on the extraction of antioxidant and plant biostimulating compounds from Chlorella sp., Chlorella vulgaris and Scenedesmus acutus. Both cell disruption methods resulted in higher extract yields from the biomass compared to freeze-dried biomass using 50% methanol as a solvent. Antioxidant activity of Chlorella extracts was generally higher than freeze-dried extracts based on the diphenylpicrylhydrazyl (DPPH) and β-carotene linoleic acid assays. However, the effectiveness of each treatment varied between microalgae strains. Sonication resulted in the highest antioxidant activity in Chlorella sp. extracts. Ball-milling gave the best results for C. vulgaris extracts in the DPPH assay. Both cell disruption methods decreased antioxidant activity in S. acutus extracts. Plant biostimulating activity was tested using the mung bean rooting assay. Damaging the membrane by freeze-drying was sufficient to release the active compounds using water extracts. In contrast, both cell disruption methods negatively affected the biological activity of the extracts. These results indicate that bioactive compounds in microalgae are sensitive to post-harvest processes and their biological activity can be negatively affected by cell disruption methods. Care must be taken to not only optimize yield but to also preserve the biological activity of the target compounds.
Open Access: Yes
Biostimulating effects of the cyanobacterium Nostoc piscinale on winter wheat in field experiments
Publication Name: South African Journal of Botany
Publication Date: 2019-11-01
Volume: 126
Issue: Unknown
Page Range: 99-106
Description:
Due to global warming, a permanent rainfall deficit and higher temperatures reduce the available water in the soil, which severely influences plant water status. Current research needs to address ways to overcome these problems in order to maintain crop yields. The beneficial effects of seaweed extracts against abiotic and biotic stress factors of plant growth is well known but the use of microalgae for the same purpose is not well described. The aim of the present work was to investigate the plant biostimulating effects of the cyanobacterium Nostoc piscinale on the winter wheat variety “Bőség.” Experiments were carried out over three years in Hungary at the Mosonmagyaróvár Faculty Farm. Freeze-dried cyanobacterium was re-suspended in water (0.3 or 1.0 g/L) and sprayed at 400 L/ha on wheat leaves at tillering or tillering and ear emergence. Root weight, relative water content (RWC), chlorophyll and proline content of leaves were measured during the vegetation period. Ear number, ear length, grain numbers in ear, thousand grain weight and yield were measured at harvest. The most economic and highest yield increase was obtained by 0.3 g/L treatment with N. piscinale at tillering and ear emergence. Beneficial effects included a stronger root system, elevated leaf RWC, higher proline content and increased leaf chlorophyll content, which remained high in plant leaves treated with N. piscinale for one or two weeks longer than in the control leaves. The high chlorophyll content extended the productive vegetation period of the treated plants. Cyanobacterium treatment increased the ear number, ear length, grain number per ear, thousand grain weight and yield of the wheat crop.
Open Access: Yes
Effect of gibberellins on growth and biochemical constituents in Chlorella minutissima (Trebouxiophyceae)
Publication Name: South African Journal of Botany
Publication Date: 2019-11-01
Volume: 126
Issue: Unknown
Page Range: 92-98
Description:
A hormonal network regulates growth processes and stress responses in vascular plants. There is evidence for a similar hormonal network in microalgae. This study investigated the effect of exogenous gibberellins (GAs) on Chlorella minutissima Fott et Nováková growth and biochemical composition. Two bioactive GAs i.e. GA3 and GA4 were applied at 10−8–10−5 M. Growth was monitored until cultures were harvested on day 7 when in an exponential growth phase. Primary metabolites (protein, chlorophyll and carotenoids) were quantified and endogenous GAs and phenolic acids were identified and quantified. GA3 had little beneficial effect on growth in C. minutissima while GA4 was inhibitory. GA application had little effect on the protein, chlorophyll and total carotenoid content. Analysis of the GA content suggested that GA3 was not readily taken up by the cells while GA4 was absorbed but not further metabolised. This high accumulation of GA4 could account for its inhibitory effect. Three phenolics acids were detected in C. minutissima i.e. p-hydroxybenzoic acid > salicylic acid > protocatechuic acid. Their concentrations were not affected by GA treatments or GA-type. The physiological role of GAs in microalgae is still unclear and further studies are required to gain clearer insight into uptake rates, metabolism and function.
Open Access: Yes
Endogenous brassinosteroids in microalgae exposed to salt and low temperature stress
Publication Name: European Journal of Phycology
Publication Date: 2018-07-03
Volume: 53
Issue: 3
Page Range: 273-279
Description:
Brassinosteroids are part of the hormonal network that regulates growth processes and stress responses in plants. There is evidence for a similar hormonal network in microalgae. In the present study, six microalgae (Chlorococcum ellipsoideum, Gyoerffyana humicola, Nautococcus mamillatus, Acutodesmus acuminatus, Protococcus viridis and Chlorella vulgaris) were subjected to salt and low temperature stress with the addition of 36 g l–1 NaCl and transfer from 25°C to 15°C. There was a rapid response to salt stress with the brassinosteroid content (mainly castasterone with lower amounts of brassinolide, homocastasterone and typhasterol) increasing within 30 min of the salt treatment and remaining at these elevated levels after 7 h. The decrease in temperature had little effect on the brassinosteroid content. This was the first study to show that endogenous brassinosteroids increase in response to abiotic stress in a number of microalgae species.
Open Access: Yes
