Ascophyllum nodosum Biostimulant Improves the Growth of Zea mays Grown Under Phosphorus Impoverished Conditions

A red seaweed Kappaphycus alvarezii-based biostimulant (AgroGain®) improves the growth of Zea mays and impacts agricultural sustainability by beneficially priming rhizosphere soil microbial community

The overuse of chemical-based agricultural inputs has led to the degradation of soil with associated adverse effects on soil attributes and microbial population. This scenario leads to poor soil health and is reportedly on the rise globally. Additionally, chemical fertilizers pose serious risks to the ecosystem and human health. In this study, foliar sprays of biostimulant (AgroGain/LBS6) prepared from the cultivated, tropical red seaweed Kappaphycus alvarezii increased the phenotypic growth of Zea mays in terms of greater leaf area, total plant height, and shoot fresh and dry weights. In addition, LBS6 improved the accumulation of chlorophyll a and b, total carotenoids, total soluble sugars, amino acids, flavonoids, and phenolics in the treated plants. LBS6 applications also improved the total bacterial and fungal count in rhizospheric soil. The V3-V4 region of 16S rRNA gene from the soil metagenome was analyzed to study the abundance of bacterial communities which were increased in the rhizosphere of LBS6-treated plants. Treatments were found to enrich beneficial soil bacteria, i.e., Proteobacteria, especially the classes Alphaproteobacteria, Cyanobacteria, Firmicutes, Actinobacteriota, Verrucomicrobiota, Chloroflexi, and Acidobacteriota and several other phyla related to plant growth promotion. A metagenomic study of those soil samples from LBS6-sprayed plants was correlated with functional potential of soil microbiota. Enrichment of metabolisms such as nitrogen, sulfur, phosphorous, plant defense, amino acid, co-factors, and vitamins was observed in soils grown with LBS6-sprayed plants. These results were further confirmed by a significant increase in the activity of soil enzymes such as urease, acid phosphatase, FDAse, dehydrogenase, catalase, and biological index of fertility in the rhizosphere of LBS6-treated corn plant. These findings conclude that the foliar application of LBS6 on Z. mays improves and recruits beneficial microbes and alters soil ecology in a sustainable manner.

Increased Accumulation of Ginsenosides in Panax ginseng Sprouts Cultivated with Kelp Fermentates

Currently, new agri-tech has been developed and adapted for the cultivation of crops using smart farming technologies, e.g., plant factories and hydroponics. Kelp (Laminaria japonica), which has a high industrial value, was considered as an alternative to chemicals for its eco-friendly and sustainably wide use in crop cultivation. In this study, a fermented kelp (FK) was developed for use in hydroponics. The FK contained various free and protein-bound amino acid compositions produced by fermenting the kelp with Saccharomyces cerevisiae. Supplementing FK as an aeroponic medium when cultivating ginseng sprouts (GSs) elevated the total phenolic and flavonoid contents. Additionally, seven ginsenosides (Rg1, Re, Rb1, Rc, Rg2, Rb2, and Rd) in GSs cultivated with FK in a smart-farm system were identified and quantified by a high-performance liquid chromatography-evaporative light scattering detector/mass spectrometry analysis. Administering FK significantly increased the ginsenosides in the GSs compared to the control group, which was cultivated with tap water. These results indicate the FK administration contributed to the increased accumulation of ginsenosides in the GSs. Overall, this study suggests that FK, which contains abundant nutrients for plant growth, can be used as a novel nutrient solution to enhance the ginsenoside content in GSs during hydroponic cultivation.

A biostimulant prepared from red seaweed Kappaphycus alvarezii induces flowering and improves the growth of Pisum sativum grown under optimum and nitrogen-limited conditions

Nitrogen (N) is one of the critical elements required by plants and is therefore one of the important limiting factors for growth and yield. To increase agricultural productivity, farmers are using excessive N fertilizers to the soil, which poses a threat to the ecosystem, as most of the applied nitrogen fertilizer is not taken up by crops, and runoff to aquatic bodies and the environment causes eutrophication, pollution, and greenhouse gas emissions. In this study, we used LBS6, a Kappaphycus alvarezii-based biostimulant as a sustainable alternative to improve the growth of plants under different NO3 - fertigation. A root drench treatment of 1 ml/L LBS6 significantly improved the growth of Pisum sativum plants grown under optimum and deficient N conditions. No significant difference was observed in the growth of LBS6-treated plants grown with excessive N. The application of LBS6 induced flowering under optimum and deficient N conditions. The total nitrogen, nitrate and ammonia contents of tissues were found to be higher in treated plants grown under N deficient conditions. The LBS6 treatments had significantly higher chlorophyll content in those plants grown under N-deficient conditions. The root drench application of LBS6 also regulated photosynthetic efficiency by modulating electron and proton transport-related processes of leaves in the light-adapted state. The rate of linear electron flux, proton conductivity and steady-state proton flux across the thylakoid membrane were found to be higher in LBS6-treated plants. Additionally, LBS6 also reduced nitrogen starvation-induced, reactive oxygen species accumulation by reduction in lipid peroxidation in treated plants. Gene expression analysis showed differential regulation of expression of those genes involved in N uptake, transport, assimilation, and remobilization in LBS6-treated plants. Taken together, LBS6 improved growth of those treated plants under optimum and nitrogen-limited condition by positively modulating their biochemical, molecular, and physiological processes.

Understanding the mode of action of AgroGain®, a biostimulant derived from the red seaweed Kappaphycus alvarezii in the stimulation of cotyledon expansion and growth of Cucumis sativa (cucumber)

Seaweed-based biostimulants are sustainable agriculture inputs that are known to have a multitude of beneficial effects on plant growth and productivity. This study demonstrates that Agrogain^® (Product code: LBS6), a Kappaphycus alvarezii-derived biostimulant induced the expansion of cucumber cotyledons. Seven days treatment of LBS6-supplementation showed a 29.2% increase in area of expanded cotyledons, as compared to the control. LBS6-treated cotyledons also showed higher amylase activity, suggesting starch to sucrose conversion was used efficiently as an energy source during expansion. To understand the mechanisms of LBS6-induced expansion, real time gene expression analysis was carried out. This revealed that LBS6-treated cotyledons differentially modulated the expression of genes involved in cell division, cell number, cell expansion and cell size. LBS6 treatment also differentially regulated the expression of those genes involved in auxin and cytokinin metabolism. Further, foliar application of LBS6 on cucumber plants being grown under hydroponic conditions showed improved plant growth as compared to the control. The total leaf area of LBS6-sprayed plants increased by 19.1%, as compared to control. LBS6-sprayed plants efficiently regulated photosynthetic quenching by reducing loss via non-photochemical and non-regulatory quenching. LBS6 applications also modulated changes in the steady-state photosynthetic parameters of the cucumber leaves. It was demonstrated that LBS6 treatment modulated the electron and proton transport related pathways which help plants to efficiently utilize the photosynthetic radiation for optimal growth. These results provide clear evidence that bioactive compounds present in LBS6 improved the growth of cucumber plants by regulating the physiological as well as developmental pathways.

The effect of rhizobia in improving the protective mechanisms of wheat under drought and supplementary irrigation conditions

Introduction

Wheat (Triticum aestivum L.) is a strategic crop and one of the world's most essential cereals, providing most of the world's calories and protein needs. Drought stress is one of the main limitations for crop production such as wheat in arid and semi-arid regions. Plants can accumulate antioxidants, carbohydrates, and stress hormones that stimulate cell and molecular regeneration under stress conditions. Irrigation saves water, improves crop photosynthesis, and increases plant ability to absorb water and elements from soil. Therefore, irrigation at the right time or supplementary irrigation can help plant growth and crop yield under drought conditions. Appropriate nutrition with fertilizers increases plants' stress tolerance. Bio-fertilizers are restorative elements used in soil to improve tolerance to stresses such as drought stress. A well-known class of bio-fertilizers is plant growth promoting rhizobacteria (PGPR). These rhizosphere bacteria affect plant development and productivity by interacting with roots. Arbuscular mycorrhizal fungi (AMF) alleviate drought stress in plants by enhancing their ability to absorb water and nutrients from the soil. Seaweed extract bio-fertilizer is organic matter used to increase crop growth and soil fertility. This bio-fertilizer is utilized as growth stimulants and food supplements. Our research analyzed the effects of rhizobia and seaweed extracts on wheat's drought resistance mechanisms.

Materials and methods

This research was conducted in Iran in the crop years of 2017–2018 and 2018–2019 in the research farm of Kurdistan University Faculty of Agriculture located in Dehgolan with coordinates 47°18′ 55″ East and 35°19′ 10″ North with an altitude of 1866 meters above sea level, 45 kilometers east It was done on the wheat plant in Sanandaj city. The experiment was conducted in the form of a split-split plot in the form of a randomized complete block design with four replications. Irrigation treatments as the main factor (no irrigation or dry-land, one irrigation in the booting stage, two irrigations in the booting and spike stages), two wheat cultivars (Sardari and Sirvan) as secondary factors, and the application of biological fertilizers at eight levels including Mycorrhiza + Nitrozist and Phosphozist, Seaweed extract + Nitrozist and Phosphozist, Mycorrhiza + Seaweed extract, Mycorrhiza + Nitrozist and Phosphozist and no application of biological fertilizers (control) as Sub-sub-factors were considered.

Results and discussion

According to the study, when bio-fertilizer was applied with once and twice supplementary irrigation levels, leaf relative water content (RWC) and soluble protein content (SPC) increased, while lack of irrigation increased malondialdehyde (MDA). In both years, bio-fertilizers, especially their combinations, increased the amount and activity of enzymatic and non-enzymatic antioxidants, including peroxidase (POD), superoxide dismutase (SOD), phenol (Phe), flavonoid (Fla), and anthocyanin (Anth). Also, it enhanced the inhibition of free radicals by 2-2-Diphenyl picryl hydrazyl (DPPH) and cleared active oxygen species. It was found that malondialdehyde (MDA) levels were very low in wheat under two times irrigation with averages of 3.3909 and 3.3865 μmol g−1 FW. The results indicated a significant positive relationship between non-enzymatic and enzymatic antioxidants such as Phe, Fla, Anth, DPPH, POD, and SOD enzymes and their role in improving stress under dry-land conditions, especially in the Sardari variety. Biological fertilizers (Mycorrhiza + Nitrozist and Phosphozist + Seaweed extract) increased wheat yield compared to the control. Furthermore, Mycorrhiza + Nitrozist and Phosphozist + Seaweed extract improved grain yield by 8.04% and 6.96% in the 1st and 2nd years, respectively. Therefore, appropriate combinations of microorganisms, beneficial biological compounds, and supplementary irrigation can reduce the adverse effects of drought stress in arid and semi-arid regions.

A Seaweed Extract-Based Biostimulant Mitigates Drought Stress in Sugarcane

Drought is one of the most important abiotic stresses responsible for reduced crop yields. Drought stress induces morphological and physiological changes in plants and severely impacts plant metabolism due to cellular oxidative stress, even in C4 crops, such as sugarcane. Seaweed extract-based biostimulants can mitigate negative plant responses caused by drought stress. However, the effects of foliar application of such biostimulants on sugarcane exposed to drought stress, particularly on plant metabolism, stalk and sugar yields, juice purity, and sugarcane technological quality, have received little attention. Accordingly, this study aimed to evaluate the effects of foliar application of a seaweed extract-based biostimulant on late-harvest sugarcane during the driest period of the year. Three experiments were implemented in commercial sugarcane fields in Brazil in the 2018 (site 1), 2019 (site 2), and 2020 (site 3) harvest seasons. The treatments consisted of the application and no application of seaweed extract (SWE) as a foliar biostimulant in June (sites 2 and 3) or July (site 1). The treatments were applied to the fourth ratoon of sugarcane variety RB855536 at site 1 and the fifth and third ratoons of sugarcane variety SP803290 at sites 2 and 3, respectively. SWE was applied at a dose of 500 ml a.i. ha^-1 in a water volume of 100 L ha^-1. SWE mitigated the negative effects of drought stress and increased stalk yield per hectare by up to 3.08 Mg ha^-1. In addition, SWE increased stalk sucrose accumulation, resulting in an increase in sugar yield of 3.4 kg Mg^-1 per hectare and higher industrial quality of the raw material. In SWE-treated plants, Trolox-equivalent antioxidant capacity and antioxidant enzyme activity increased, while malondialdehyde (MDA) levels decreased. Leaf analysis showed that SWE application efficiently improved metabolic activity, as evidenced by a decrease in carbohydrate reserve levels in leaves and an increase in total sugars. By positively stabilizing the plant's cellular redox balance, SWE increased biomass production, resulting in an increase in energy generation. Thus, foliar SWE application can alleviate drought stress while enhancing sugarcane development, stalk yield, sugar production, and plant physiological and enzymatic processes.

A Global Network Meta-Analysis of the Promotion of Crop Growth, Yield, and Quality by Bioeffectors

Bioeffector (BE) application is emerging as a strategy for achieving sustainable agricultural practices worldwide. However, the effect of BE on crop growth and quality is still controversial and there is still no adequate impact assessment that determines factors on the efficiency of BE application. Therefore, we carried out a network metaanalysis on the effect of BEs using 1,791 global observations from 186 studies to summarize influencing factors and the impact of BEs on crop growth, quality, and nutrient contents. The results show that BEs did not only improve plant growth by around 25% and yield by 30%, but also enhanced crop quality, e.g., protein (55% increase) and soluble solids content (75% increase) as well as aboveground nitrogen (N) and phosphate (P) content by 28 and 40%, respectively. The comparisons among BE types demonstrated that especially non-microbial products, such as extracts and humic/amino acids, have the potential to increase biomass growth by 40-60% and aboveground P content by 54-110%. The soil pH strongly influenced the efficiency of the applied BE with the highest effects in acidic soils. Our results showed that BEs are most suitable for promoting the quality of legumes and increasing the yield of fruits, herbs, and legumes. We illustrate that it is crucial to optimize the application of BEs with respect to the right application time and technique (e.g., placement, foliar). Our results provide an important basis for future research on the mechanisms underlying crop improvement by the application of BEs and on the development of new BE products.

Algae and Their Metabolites as Potential Bio-Pesticides

An increasing human population necessitates more food production, yet current techniques in agriculture, such as chemical pesticide use, have negative impacts on the ecosystems and strong public opposition. Alternatives to synthetic pesticides should be safe for humans, the environment, and be sustainable. Extremely diverse ecological niches and millions of years of competition have shaped the genomes of algae to produce a myriad of substances that may serve humans in various biotechnological areas. Among the thousands of described algal species, only a small number have been investigated for valuable metabolites, yet these revealed the potential of algal metabolites as bio-pesticides. This review focuses on macroalgae and microalgae (including cyanobacteria) and their extracts or purified compounds, that have proven to be effective antibacterial, antiviral, antifungal, nematocides, insecticides, herbicides, and plant growth stimulants. Moreover, the mechanisms of action of the majority of these metabolites against plant pests are thoroughly discussed. The available information demonstrated herbicidal activities via inhibition of photosynthesis, antimicrobial activities via induction of plant defense responses, inhibition of quorum sensing and blocking virus entry, and insecticidal activities via neurotoxicity. The discovery of antimetabolites also seems to hold great potential as one recent example showed antimicrobial and herbicidal properties. Algae, especially microalgae, represent a vast untapped resource for discovering novel and safe biopesticide compounds.

Recent Advances in the Molecular Effects of Biostimulants in Plants: An Overview

As the world develops and population increases, so too does the demand for higher agricultural output with lower resources. Plant biostimulants appear to be one of the more prominent sustainable solutions, given their natural origin and their potential to substitute conventional methods in agriculture. Classified based on their source rather than constitution, biostimulants such as humic substances (HS), protein hydrolysates (PHs), seaweed extracts (SWE) and microorganisms have a proven potential in improving plant growth, increasing crop production and quality, as well as ameliorating stress effects. However, the multi-molecular nature and varying composition of commercially available biostimulants presents challenges when attempting to elucidate their underlying mechanisms. While most research has focused on the broad effects of biostimulants in crops, recent studies at the molecular level have started to unravel the pathways triggered by certain products at the cellular and gene level. Understanding the molecular influences involved could lead to further refinement of these treatments. This review comprises the most recent findings regarding the use of biostimulants in plants, with particular focus on reports of their molecular influence.

Biostimulants Application: A Low Input Cropping Management Tool for Sustainable Farming of Vegetables

Biostimulants, are a diverse class of compounds including substances or microorganism which have positive impacts on plant growth, yield and chemical composition as well as boosting effects to biotic and abiotic stress tolerance. The major plant biostimulants are hydrolysates of plant or animal protein and other compounds that contain nitrogen, humic substances, extracts of seaweeds, biopolymers, compounds of microbial origin, phosphite, and silicon, among others. The mechanisms involved in the protective effects of biostimulants are varied depending on the compound and/or crop and mostly related with improved physiological processes and plant morphology aspects such as the enhanced root formation and elongation, increased nutrient uptake, improvement in seed germination rates and better crop establishment, increased cation exchange, decreased leaching, detoxification of heavy metals, mechanisms involved in stomatal conductance and plant transpiration or the stimulation of plant immune systems against stressors. The aim of this review was to provide an overview of the application of plant biostimulants on different crops within the framework of sustainable crop management, aiming to gather critical information regarding their positive effects on plant growth and yield, as well as on the quality of the final product. Moreover, the main limitations of such practice as well as the future prospects of biostimulants research will be presented.