DAY 1Wednesday, 13 November 2024

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The warming global climate and associated changes in severe weather events provides substantial stress to growing plants. Plants have evolved elaborate mechanisms that enhance their resilience to stress including synthesis of protective specialized metabolites. By uncovering the mechanisms by which these molecules are synthesized and how they protect plants from stress, we can define mechanisms to overproduce these compounds in plants and define compounds that may be suited for use as biostimulants to more rapidly protect a wide range of plants from rapidly increasing environmental stress.

We have seen that the growth of Biologicals/Biostimulants have outpaced the growth of ag chemicals.

#1 - Biostimulants & Microbials remain attractive. Why?

#2 - What do start-ups need to do to be successful? Examples?

#3 - Highlight technology breakthrough(s) that have helped your growth?

#4 - How do we make this sector more attractive to the new generation of scientists?

#5 - Biggest opportunities for investment?

#6 - Investor insight: What areas of opportunity do you seek besides Nitrogen-fixing and Regenerative agriculture?

The threats of climate change highlight the need to develop biologically rational regulatory frameworks for a more resilient agriculture. We proposed the overview machinery that how and to what extend plants optimize their response through plant regulatory networks (PGRN) to environmental stresses (drought, heat, salinity, heavy metal, etc.) and agricultural treatments (biostimulants, irrigation, fertilization, microbial amendments, breeding techniques, etc.). This talk reviews and discusses the roles of biostimulants and plant growth regulators, in the perspective of global regulatory guidelines.

The rising use of plant biostimulants, recognized for enhancing growth, resilience, and stress tolerance, has largely overlooked root research. This situation prevents a better understanding of the effect of biostimulants at the whole plant, whereas the root is the site of water and mineral nutrition, the rhizosphere and symbioses. In order to provide initial insights into this new area of research, we have developed a 'rhizobox' system coupled with a specific 'software' method to monitor the direct response of the root to biostimulant supplementation. These experiments have been carried out in controlled growth room and allow us both to finely modulate nutrient solutions and to set up a range of water stress: mild, moderate and high stress. We have also adapted a set of imaging and root reading software to finely analyse the architecture and kinetic growth of the root system. This protocol was set up using a protein hydrolysate biostimulant derived from chemically hydrolysed chicken feathers with a composition of 88% free amino acids. The efficiency of the biostimulant on the plant’s aerial components has been established (Malecange et al., 2022), however its effect on the root system remains unknown. Initial results support a direct effect on root architecture (branching and length of the primary root) and growth (up to 100%), which is dependent on biostimulant concentration and plant nitrogen and water status. This innovative approach opens up the possibility of a holistic understanding of the plant response to biostimulants and therefore better use to improve crop resilience.

Humic acids (HA) have been shown to modify plant root membrane potential, thereby influencing cell growth and enzymatic activity, ultimately promoting plant growth. However, while the effects of root-applied HA on plants are well-documented, the effects of foliar-sprayed HA remain poorly understood. In this study, we investigated the response of corn plants to foliar-sprayed HA derived from an oxidized sub bituminous coal. We conducted a dose-response experiment using concentrations ranging from 0 to 40 mg carbon/L in 50% Hoagland’s solution over a period of 10 days. We scanned plants to evaluate root morphology, and isolated membrane vesicles from corn leaves and roots to measure plasma membrane H+-ATPase and NADH oxidase activity. The optimal concentration of HA (30 mg carbon/L) led to a 20% enhancement in root fresh and dry weight, total root length, root surface area, and finer root diameter classes. Our findings suggest a mechanism by which foliar-sprayed HA stimulates growth, demonstrating its ability to regulate both root and leaf plasma membrane H+-ATPase and NADH oxidase activity. These effects are likely associated with improvements in root foraging capacity, such as increased surface area and finer roots, potentially attributable to the interplay between antioxidants and pro-oxidants presented by the presence of flavonoid and quinone-like components, respectively, as evidenced by the high content of condensed aromatic structures observed in both FT-ICR and 13C-NMR analyses. We propose a putative long-distance signaling mechanism of HA from shoot to root, wherein regulation of plant redox systems contributes to root development.

The future of biostimulants in agriculture must take human health into consideration. We posit that Brassinosteroids (BRs) increase plant and human health. BRs are endogenous plant hormones, present everywhere in a plant, acting at low concentrations to regulate plant growth and development. Molecular and cellular mechanisms of BR function have been well studied and are known to regulate elongation growth, response to light, development and differentiation, fertility, and senescence. BRs regulate the expression of several genes in plants (1). In rice, BRs promote grain yield (2), in corn, BRs regulate fertility (3). BR-biostimulant benefits have been shown in cotton, wheat, rapeseed, grape, potato, petunia, and more (4), including specialty crops (unpublished data). BRs increase resistance to a broad range of diseases (5) and abiotic stresses, including drought (6). BRs promote the expression of antioxidants (4). Benefits of BR-biostimulants go beyond plant performance. Even high doses of BRs showed no toxicity in Wistar rats (7). Oral doses of BR increased physical fitness by 67% in rats (8). Studies show BRs inhibit cancer cell growth in breast, prostate, colon and lung (9). BRs are natural compounds with potential for treating cancer without affecting normal cell growth (9, 10). BRs are reported to be chemopreventive, anti-inflammatory, neuroprotective, and antidiabetic. Working with a BR-biostimulant, we are gaining remarkable insights relevant to the rapidly growing biostimulant industry and its scope in promoting both plant and human health. Research will be presented to expand the opportunities of biostimulants in improving food, human and planetary health.Rajnish Khanna, Senior Investigator, Carnegie Institution for Science, USA

Recent interest in microalgae as potential biostimulants has surged with studies highlighting their role in growth enhancement, abiotic stress remediation, and economic and environmental benefits. Despite extensive research across various plant species, the various biostimulant effects observed are significantly influenced by factors including the microalgal species, application method, extraction technique, plant developmental stage, and environmental conditions.


To address these complexities, we propose a quick, thorough, and standardized testing method using the model organism Arabidopsis thaliana. This method combines a solid-plate germination assay with two potting soil assays, facilitating a comprehensive screening of the whole plant development cycle for potential biostimulant effects.


We investigated the effects of six microalgae species at varying concentrations and application methods (soil mixture, irrigation and foliar spray), ranging from well-recognized biostimulants like Arthrospira platensis and Chlorella vulgaris to lesser-known species such as Nannochloropsis gaditana, Dunaliella salina, Isochrysis galbana, and Porphyridium purpureum. Our results reveal distinct biostimulant potentials for each species. Notably, N. gaditana mitigates drought stress by enhancing root length in early seedling development and stimulating fresh weight accumulation in further vegetative growth. D. salina improves salinity tolerance under specific application treatments, and P. purpureum significantly enhances generative growth, increasing flowering stems' fresh weight by 44% through a foliar treatment.


Our findings accentuate the biostimulant activity of each microalgae species under specific conditions, demonstrating the efficacy of our standardized, high-throughput assays. Additionally, our results highlight the critical impact of application techniques and environmental conditions on the effectiveness of biostimulants.
Bram Vangenechten, PhD Student, KU Leuven, Belgium

Generated annually in large quantities from meat processing industries, chicken feather consists of approximately 90% keratin, showing high potential for production of high-value biostimulants through enzymatic hydrolysis. Under the impetus of stricter fertilizing regulations, the biostimulant potential of hydrolysates has gain an increasing attention in plant production systems. Despite the continuous results from foliar application or seed treatment, the potential of hydrolysates under soil application are still uncertain and rarely investigated. This study aimed to fill in the knowledge gap through a pot trial using two hydrolysates derived from chicken feather, with either high (> 15 kDa, labelled as HH) or low molecular weight components (<3 kDa, labelled as LH). The hydrolysates were applied in soil at 10 kg N ha-1 with chemical fertiliser (CF, using urea with 46% N) to reach a total applied N at low (10 kg ha-1), medium (45 kg ha-1) and high (90 kg ha-1) levels, respectively. Overall, the total ryegrass shoot and root biomass revealed significant positive correlations with the N dose (r = 0.55-0.87, p < 0.001). When compared to CF at the same N dose, the shoot and root biomass treated with HH and LH were lower, comparable, and higher at low, middle and high N doses, respectively. A converse trend was observed for the root length, suggesting a potentially higher resistant to N stress with the application of both HH and LH, and a potentially stimulated nutrient use efficiency at high N dose.

Phosphate-solubilizing bacteria can improve plant photosynthesis by increasing phosphorus (P) use efficiency in the soil-plant system, an essential nutrient in energy storage and transfer. Thus, this research investigated the effects of Bacillus velezensis UFV 3918 (Bv) (equivalent to 108 CFU mL–1) inoculation combined with mono ammonium phosphate (MAP) doses on sugarcane physiology and biochemistry. The greenhouse experiment was conducted in a completely randomized design with six treatments, including absolute control (AC), commercial control (CC) at the recommended MAP dose, and different combinations of Bv and doses of MAP, with four replicates. Statistical analysis was conducted on the data, including ANOVA and Scott-Knott test (p≤0.05). Bv (without MAP) increased total chlorophyll content by 10.7% compared to CC, which increased the linear electron flow through photosystem II by 32%. Photochemical efficiency favored the superior biochemical performance of Bv, with notable increases of 64.3%, 52.6%, and 100% in net CO2 assimilation, stomatal conductance, and carboxylation efficiency, respectively, compared to CC. Moreover, Bv showed 16.4% higher leaf acid phosphatase (LAP) activity than CC, underscoring the phosphate solubilization potential of the UFV 3918 strain, and it explains why LAP was the most important biochemical variable for shoot biomass production. Interestingly, Bv inoculation allowed for a decrease in MAP doses without impairing photosynthetic efficiency or shoot biomass production. The findings provided insights for ongoing research, which evaluates the potential for phosphorus solubilization by the strain UFV 3918 using filter cake and reactive rock phosphate in sugarcane in contrasting production environments, with surprising new results.

Ethylene accumulation in response to abiotic stresses can cause growth inhibition and premature senescence of plants. Endophytic rhizobacteria that suppresses stress-induced ethylene synthesis in plant tissues may promote plant health and tolerance to abiotic stress (Errickson et al., 2023). The objective of this study was to investigate the physiological health effects of novel strains of Paraburkholderia aspalathi producing 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase enzymes (ethylene inhibitor) on plant tolerance to heat stress and underlying metabolic regulatory mechanisms of P. aspalathi-for heat tolerance in creeping bentgrass (Agrostis stolonifera). A novel strain of P. aspalathi, ‘WSF23’, with strong ACC deaminase activity was used to inoculate the roots of plants subjected to heat stress (35oC). Inoculation with WSF23 rhizobacteria resulted in significant increased in shoot and root growth during heat stress. The up-regulation of metabolites within plants tissues due to the bacterial colonization, particularly associated with antioxidant and stress defense, could contribute to ACC deamination bacteria-improved heat tolerance in cool-season grass species.

Crop plants are often exposed to environmental stress conditions which poses a serious threat to food security and sustainable development. Expected increases in atmospheric CO₂ and air temperature will further aggravate the detrimental impacts of the stress conditions on crop production. A strong body of evidence shows that balanced mineral nutrition is highly effective in mitigating the adverse effects of environmental stress conditions on crop productivity, especially in case of drought stress, extreme temperatures, excess light, aluminium toxicity and diseases. Optimal mineral nutrition is essential to support a range of physiological functions which enable plant adaptation to changing environment and to maintain yield under stressful environments. This presentation will highlight examples of the effect of plant nutrition on plant adaptation to stress with a focus on the role of nutrient elements in cell wall and membrane stability, the production of bioactive and antioxidative compounds, stomatal regulation, stress-signalling mechanisms, carbon allocation, and rhizosphere microbiome. This presentation will also discuss how an understanding of plant mineral nutrition is critical for the effective use of biostimulants in cropping systems.

Seaweed (ascophyllan nodosum) extracts (SWE) are widely used for active components in plant biostimulant products. The foliar application of SWE has been shown to improve plant tolerance to various abiotic and biotic stresses such as drought, heat, and cold temperature. The beneficial effects of SWE on plant stress tolerance have mainly been attributed to its hormone (especially cytokinin and auxin) components. By using bioassays and GC-MS/MS, the hormonal activity of SWE has been analyzed. Studies were carried out to prove the role of hormonal activity is an important factor responsible for the positive effects of SWE for improving abiotic stress tolerance by using bioassay and GC-MS/MS analysis of hormones in the SWEs. Physiological and metabolic analysis showed that SWE could improve plant stress tolerance by multiple regulatory pathways, including relating hormonal balance, enhancing antioxidant defense, and osmotic adjustment, protecting photosynthetic function, and improving root growth and viability. Recent research also showed that SWE could regulate nitrate reductase activity, plant antioxidant and hormone-related gene expressions. The SWE application in interaction with other biostimulants for enhancing plant abiotic stress tolerance will also be presented.

To satisfy global food markets with continuous supply of fruits and vegetable crops during the whole season, growers in arid and semi-arid regions have increased the use of salinized water in irrigation regimes1. While plant biostimulants have been reported to be an effective solution to tackle salinity stress in different crops, the key genes and metabolic pathways involved in these tolerance processes remain unclear2-4. This study focused on integrating phenotypic, physiological, biochemical and transcriptome data obtained from different tissues of tomato plants (cv. Micro-Tom) subjected to a saline irrigation water program for 61 days (EC: 5.8 dS/m) and treated with a protein hydrolysate and Ascophyllum nodosum-derived biostimulant. The biostimulant application was associated with the overexpression of transporter genes related to ion homeostasis (e.g., HKT1;2), restricting Na+ translocation from roots to leaves and promoting K+ accumulation in roots. It allowed the maintenance of higher K+/Na+ ratios in both leaf and root tissue. A more efficient osmotic adjustment was characterized by a significant increase in RWC, which was associated with osmolyte accumulation and upregulation of genes related to aquaporins (e.g., PIP2.1). Higher content of photosynthetic pigments, increased expression of genes involved in photosynthetic efficiency and chlorophyll biosynthesis (e.g., LHC) and enhanced primary C and N metabolic mechanisms were also observed, leading to higher fruit yield and fruit number (47.5% and 32.5%, respectively). Overall, it can be concluded that this novel biostimulant can provide long-term protective effects on salinity stressed tomato plants through a well-defined mode of action in different plant tissues.