Effects of foliar application of amino acid liquid fertilizers, with or without Bacillus amyloliquefaciens SQR9, on cowpea yield and leaf microbiota

Bacillus velezensis SQR9 promotes plant growth through colonization and rhizosphere-phyllosphere bacteria interaction

The rhizosphere and phyllosphere of plants are home to a diverse range of microorganisms that play pivotal roles in ecosystem services. Consequently, plant growth-promoting bacteria (PGPB) are extensively utilized as inoculants to enhance plant growth and boost productivity. Despite this, the interactions between the rhizosphere and phyllosphere, which are influenced by PGPB inoculation, have not been thoroughly studied to date. In this study, we inoculated Bacillus velezensis SQR9, a PGPB, into the bulk soil, rhizosphere or phyllosphere, and subsequently examined the bacterial communities in the rhizosphere and phyllosphere using amplicon sequencing. Our results revealed that PGPB inoculation increased its abundance in the corresponding compartment, and all treatments demonstrated plant growth promotion effects. Further analysis of the sequencing data indicated that the presence of PGPB exerted a more significant impact on bacterial communities in both the rhizosphere and phyllosphere than in the inoculation compartment. Notably, the PGPB stimulated similar rhizosphere-beneficial microbes regardless of the inoculation site. We, therefore, conclude that PGPB can promote plant growth both directly and indirectly through the interaction between the rhizosphere and phyllosphere, leading to the enrichment of beneficial microorganisms.

Amino Acids Biostimulants and Protein Hydrolysates in Agricultural Sciences

The effects of different types of biostimulants on crops include improving the visual quality of the final products, stimulating the immune systems of plants, inducing the biosynthesis of plant defensive biomolecules, removing heavy metals from contaminated soil, improving crop performance, reducing leaching, improving root development and seed germination, inducing tolerance to abiotic and biotic stressors, promoting crop establishment and increasing nutrient-use efficiency. Protein hydrolysates are mixtures of polypeptides and free amino acids resulting from enzymatic and chemical hydrolysis of agro-industrial protein by-products obtained from animal or plant origins, and they are able to alleviate environmental stress effects, improve growth, and promote crop productivity. Amino acids involve various advantages such as increased yield and yield components, increased nutrient assimilation and stress tolerance, and improved yield components and quality characteristics. They are generally achieved through chemical or enzymatic protein hydrolysis, with significant capabilities to influence the synthesis and activity of some enzymes, gene expression, and redox-homeostasis. Increased yield, yield components, and crop quality; improved and regulated oxidation-reduction process, photosynthesis, and physiological activities; decreased negative effects of toxic components; and improved anti-fungal activities of plants are just some of the more important benefits of the application of phenols and phenolic biostimulants. The aim of this manuscript is to survey the impacts of amino acids, different types of protein hydrolysates, phenols, and phenolic biostimulants on different plants by presenting case studies and successful paradigms in several horticultural and agricultural crops.

Optimization of liquid fertilizer management improves grain yield, biomass accumulation, and nutrient uptake of late-season indica fragrant rice

BACKGROUND

The use of liquid fertilizer is an effective measure to increase rice yield and nitrogen use efficiency. There has been a lack of information regarding the effects on the grain yield, biomass accumulation, and nutrient uptake in late-season indica fragrant rice of split fertilizer application and of nitrogen management in liquid fertilizer application.

RESULTS

A 2-year field experiment was carried out during 2019 and 2020 with two fragrant rice cultivars grown under differing fertilizer management treatments. Results showed that the fertilization treatments affected the grain yield, yield components, biomass accumulation, and nutrient accumulation significantly. The mean nitrogen recovery efficiency with liquid fertilizer management was greater than in a control treatment corresponding to a practice commonly used by farmers (H2). The effects of nitrogen metabolism enzymes in the leaves of both rice cultivars were stronger with liquid fertilizer treatments than with H2. Grain yield was positively associated with the effective panicle number, spikelets per panicle, dry matter accumulation, N and K accumulation, and the nitrogen metabolism enzymes.

CONCLUSIONS

Optimized liquid fertilizer management increases biomass accumulation, nitrogen utilization efficiency, and nitrogen metabolism. It stabilizes yields and increases the economic benefits of late-season indica fragrant rice. © 2023 Society of Chemical Industry.

Effects of Valine and Urea on Carbon and Nitrogen Accumulation and Lignin Content in Peach Trees

Nitrogen availability and uptake levels can affect nutrient accumulation in plants. In this study, the effects of valine and urea supplementation on the growth of new shoots, lignin content, and carbon and the nitrogen metabolism of 'Ruiguang 39/peach' were investigated. Relative to fertilization with urea, the application of valine inhibited shoot longitudinal growth, reduced the number of secondary shoots in autumn, and increased the degree of shoot lignification. The application of valine also increased the protein level of sucrose synthase (SS) and sucrose phosphate synthase (SPS) in plant leaves, phloem, and xylem, thereby increasing the soluble sugar and starch content. It also resulted in an increase in nitrate reductase (NR), glutamine synthase (GS), and glutamate synthase (GOGAT) protein levels, with an increase in plant contents of ammonium nitrogen, nitrate nitrogen, and soluble proteins. Although urea application increased the protein level of carbon- and nitrogen-metabolizing enzymes, the increase in plant growth reduced the overall nutrient accumulation and lignin content per unit tree mass. In conclusion, the application of valine has a positive effect on increasing the accumulation of carbon and nitrogen nutrients in peach trees and increasing the lignin content.

Harnessing bacterial strain from rhizosphere to develop indigenous PGPR consortium for enhancing lobia (Vigna unguiculata) production

The rhizosphere microbes play a key role in plant nutrition and health. However, the interaction of beneficial microbes and Vigna unguiculata (lobia) production remains poorly understood. Thus, we aimed to isolate and characterize the soil microbes from the rhizosphere and develop novel microbial consortia for enhancing lobia production. Fifty bacterial strains were isolated from the rhizosphere soil samples of lobia. Finally, five effective strains (e.g., Pseudomonas sp. IESDJP-V1 and Pseudomonas sp. IESDJP-V2, Serratia marcescens IESDJP-V3, Bacillus cereus IESDJP-V4, Ochrobactrum sp. IESDJP-V5) were identified and molecularly characterized by 16 S rDNA gene amplification. All selected strains showed positive plant growth promoting (PGP) properties in broth culture. Based on morphological, biochemical, and plant growth promoting activities, five effective isolated strains and two collected strains (Azospirillum brasilense MTCC-4037 and Paenibacillus polymyxa BHUPSB17) were selected. The pot trials were conducted with seed inoculations of lobia (Vigna unguiculata) var. Kashi Kanchan with thirty treatments and three replications. The treatment combination T3 (Pseudomonas sp. IESDJP-V2), T14 (Pseudomonas sp. IESDJP-V2 + A. brasilense), T26 (Pseudomonas sp. IESDJP-V1+ B. cereus IESDJP-V4 + P. polymyxa) and T27 (IESDJP-V1+ IESDJP-V5+ A. brasilense) were recorded for enhancing plant growth attributes, yield, nutritional content like protein, total sugar, flavonoid and soil properties as compared to control and others. The effective treatments T3 (Pseudomonas sp.), T14 (Pseudomonas sp. IESDJP-V2 + A. brasilense), T26 (Pseudomonas sp. IESDJP-V1+ B. cereus IESDJP-V4 + P. polymyxa) and T27 (IESDJP-V1+ IESDJP-V5+ A. brasilense) recorded as potential PGPR consortium for lobia production. The treatment of single (Pseudomonas sp.), duel (IESDJP-V2 + A. brasilense) and triple combination (IESDJP-V1+ IESDJP-V4 + P. polymyxa) and (IESDJP-V1+ IESDJP-V5+ A. brasilense) can be further used for developing effective indigenous consortium for lobia production under sustainable farming practices. These PGPR bio-inoculant will be cost-effective, environment-friendly and socially acceptable.

Preparation, biocontrol activity and growth promotion of biofertilizer containing Streptomyces aureoverticillatus HN6

Nowadays, due to the excessive dependence on chemical fertilizers and pesticides in agricultural production, many problems, such as soil hardening and soil-borne diseases, have become increasingly prominent, which seriously restrict the sustainable development of agriculture. The application of microbial fertilizer prepared by biocontrol microorganisms can not only improve soil structure and increase fertility but also have the function of controlling diseases. Streptomyces aureoverticillatus HN6 has obvious disease prevention and growth promotive effect, which can improve the rhizosphere fertility of plants and even regulate the rhizosphere microbial community of plants. Based on the comparison of frame composting and natural composting, we used the response surface method to optimize the preparation conditions of Streptomyces HN6 bacterial fertilizer. The results showed that natural composting not only produced higher composting temperatures and maintained long high temperature periods in accordance with local conditions, but was also more suitable for composting in the field according to local conditions. Therefore, the substrate's conductivity changed more, the ash accumulation increased, and the substrate decomposed more thoroughly. Thus, this composting method is highly recommended. Additionally, Streptomyces HN6 microbial fertilizer EC20 can reduce cowpea fusarium wilt and promote cowpea growth. The number of plant leaves, plant height and fresh weight, increased significantly in the microbial fertilizer EC20. Moreover, Streptomyces HN6 fertilizer EC20 could significantly induce soil invertase, urease and catalase activities. Our study highlights the potential use of Streptomyces HN6 as a biofertilizer to improve plant productivity and biological control of plant pathogenic fungi.

An amino acid fertilizer improves the emergent accumulator plant Nasturtium officinale R. Br. phytoremediation capability for cadmium-contaminated paddy soils

Cadmium (Cd) contamination of paddy soil affects safe crop production. This study aimed to evaluate the effects of plant biostimulant amino acid fertilizer on the phytoremediation capability of an emergent accumulator plant Nasturtium officinale R. Br. for Cd-contaminated paddy soils. A pot study was carried out to study the effects of different concentrations of amino acid fertilizer on the Cd accumulation of N. officinale grown in Cd-contaminated paddy soil. The amino acid fertilizer increased the biomass of N. officinale. The amino acid fertilizer concentration exhibited a quadratic polynomial regression relationship with the root and shoot biomass. The fertilizer also increased the photosynthetic pigment (chlorophyll and carotenoid) contents, peroxidase (POD; EC 1.11.1.7) activity, and catalase (CAT; EC 1.11.1.6) activity of N. officinale, but decreased the soluble protein content and had no significant effect on the superoxide dismutase (SOD; EC 1.15.1.1) activity. Furthermore, the amino acid fertilizer increased the Cd content and Cd extraction of N. officinale. The shoot Cd extraction increased by 29.06%, 63.05%, 77.22%, and 17.40% at 1500-, 1200-, 900-, and 600-fold dilutions of the amino acid fertilizer, respectively, compared with the control. Moreover, the amino acid fertilizer promoted the Cd transport from the roots to shoots of N. officinale. The amino acid fertilizer concentration also exhibited a quadratic polynomial regression relationship with the root Cd content, shoot Cd content, root Cd extraction, and shoot Cd extraction, respectively. The correlation, grey relational, and path analyses revealed that the root biomass, shoot biomass, chlorophyll content, catalase activity, shoot Cd content, and root Cd extraction were closely associated with the shoot Cd extraction. Therefore, the amino acid fertilizer can promote Cd uptake and improve the phytoremediation capability of N. officinale to remediate Cd-contaminated paddy soils, and 900-fold dilution is the most suitable concentration.

Integrative analysis of transcriptome and metabolome reveals the mechanism of foliar application of Bacillus amyloliquefaciens to improve summer tea quality (Camellia sinensis)

Bacillus amyloliquefaciens is a promising microbial agent for quality improvement in crops; however, the effects of B. amyloliquefaciens biofertilizers on tea leaf metabolites are relatively unknown. Herein, a combination of metabolome profiling and transcriptome analysis was employed to investigate the effects of foliar spraying with B. amyloliquefaciens biofertilizers on tea leaf quality. The tea polyphenol to amino acid ratio (TP/AA), catechin, and caffeine levels decreased, but theanine level increased in tea leaves after foliar spraying with B. amyloliquefaciens. The differentially accumulated metabolites included flavonoids, phenolic acids, organic acids, amino acids, and carbohydrates. The decrease in catechin was correlated with the catechin/flavonoid biosynthesis pathway. The AMPD gene was highly associated with caffeine content, while the GOGAT gene was associated with theanine accumulation. Foliar spraying with B. amyloliquefaciens biofertilizers may improve summer tea quality. Our findings provide a basis for the application of B. amyloliquefaciens biofertilizers in tea plants and new insights on summer tea leaf resource utilization.

Fertilizers and Fertilization Strategies Mitigating Soil Factors Constraining Efficiency of Nitrogen in Plant Production

Fertilizer Use Efficiency (FUE) is a measure of the potential of an applied fertilizer to increase its impact on the uptake and utilization of nitrogen (N) present in the soil/plant system. The productivity of N depends on the supply of those nutrients in a well-defined stage of yield formation that are decisive for its uptake and utilization. Traditionally, plant nutritional status is evaluated by using chemical methods. However, nowadays, to correct fertilizer doses, the absorption and reflection of solar radiation is used. Fertilization efficiency can be increased not only by adjusting the fertilizer dose to the plant's requirements, but also by removing all of the soil factors that constrain nutrient uptake and their transport from soil to root surface. Among them, soil compaction and pH are relatively easy to correct. The goal of new the formulas of N fertilizers is to increase the availability of N by synchronization of its release with the plant demand. The aim of non-nitrogenous fertilizers is to increase the availability of nutrients that control the effectiveness of N present in the soil/plant system. A wide range of actions is required to reduce the amount of N which can pollute ecosystems adjacent to fields.

Enhanced Yield of Pepper Plants Promoted by Soil Application of Volatiles From Cell-Free Fungal Culture Filtrates Is Associated With Activation of the Beneficial Soil Microbiota

Plants communicate with microorganisms by exchanging chemical signals throughout the phytosphere. Such interactions are important not only for plant productivity and fitness, but also for terrestrial ecosystem functioning. It is known that beneficial microorganisms emit diffusible substances including volatile organic compounds (VOCs) that promote growth. Consistently, soil application of cell-free culture filtrates (CF) of beneficial soil and plant-associated microorganisms enhances plant growth and yield. However, how this treatment acts in plants and whether it alters the resident soil microbiota, are largely unknown. In this work we characterized the responses of pepper (Capsicum annuum L.) plants cultured under both greenhouse and open field conditions and of soil microbiota to soil application of CFs of beneficial and phytopathogenic fungi. To evaluate the contribution of VOCs occurring in the CFs to these responses, we characterized the responses of plants and of soil microbiota to application of distillates (DE) of the fungal CFs. CFs and their respective DEs contained the same potentially biogenic VOCs, and application of these extracts enhanced root growth and fruit yield, and altered the nutritional characteristics of fruits. High-throughput amplicon sequencing of bacterial 16S and fungal ITS rRNA genes of the soil microbiota revealed that the CF and DE treatments altered the microbial community compositions, and led to strong enrichment of the populations of the same beneficial bacterial and fungal taxa. Our findings show that CFs of both beneficial and phytopathogenic fungi can be used as biostimulants, and provide evidence that VOCs occurring in the fungal CFs act as mediators of the plants' responses to soil application of fungal CFs through stimulation of the beneficial soil microbiota.

Foliar N Application on Tea Plant at Its Dormancy Stage Increases the N Concentration of Mature Leaves and Improves the Quality and Yield of Spring Tea

Over 30% of the Chinese tea plantation is supplied with excess fertilizer, especially nitrogen (N) fertilizer. Whether or not foliar N application on tea plants at the dormancy stage could improve the quality of spring tea and be a complementary strategy to reduce soil fertilization level remains unclear. In this study, the effects of foliar N application on tea plants were investigated by testing the types of fertilizers and their application times, and by applying foliar N under a reduced soil fertilization level using field and ¹⁵N-labeling pot experiments. Results showed that the foliar N application of amino acid liquid fertilizer two times at the winter dormancy stage was enough to significantly increase the N concentration of the mature leaves and improved the quality of spring tea. The foliar application of 2% urea or liquid amino acid fertilizer two times at the winter dormancy stage and two times at the spring dormancy stage showed the best performance in tea plants among the other foliar N fertilization methods, as it reduced the soil fertilization levels in tea plantations without decreasing the total N concentration of the mature leaves or deteriorating the quality of spring tea. Therefore, foliar N application on tea plants at its dormancy stage increases the N concentration of the mature leaves, improves the quality and yield of spring tea, and could be a complementary strategy to reduce soil fertilization levels.

Thermal hydrolyzed food waste liquor as liquid organic fertilizer

Thermal hydrolysis (TH) is an efficient technology for food waste (FW) management. This study investigated the nutrients released from FW under various TH temperature (140, 160, 180, 200 and 220 °C) and evaluated the feasibility of the hydrolyzed liquor (HL) as liquid organic fertilizer. The phytotoxicity and biotoxicity of HL was analyzed using wheat seed and Pseudomonas putida. Results revealed that TH could effectively solubilize FW and release nutrients (N, P and K) and organic substances. The highest content of total nitrogen (TN, 1685 mgN/L) and phosphorus (TP, 235 mgP/L) in the HL was obtained under 180 °C. The K⁺ was 278-293 mg/L regardless of treatment temperature. Secondary nutrients (Ca and Mg) and micro metals (Fe, Cu, Zn, Al, Co and Mn) were all detected at relatively high level, while heavy metals (As and Cd) were generally lower than 0.5 mg/L. Twenty types of free amino acid were identified and the maximum total concentration was 4965.13 mg/L. 2% HL displayed higher germination index (>80%) and enhanced root and shoot lengths. No biotoxicity was observed as confirmed by the bioassay. This study proposes a feasible method to solubilize food waste and produce liquid organic fertilizer.

Rs-198 Liquid Biofertilizers Affect Microbial Community Diversity and Enzyme Activities and Promote Vitis vinifera L. Growth

Chemical fertilizers were applied on perennial tree vines to obtain high yields, which have resulted in considerable deterioration of soil quality, and it is likely to have negative impacts on the development of the grape industry. In this study, P. putida Rs-198 liquid biofertilizer (Rs198LBF) was inoculated into grape rhizosphere soils to assess its influence on grape growth and microbial community. Field experiment results showed that grape growth and quality increased depending on the concentrations of Rs198LBF applications. The berry weight, length, and width in addition with 60 ml Rs198LBF (1.44 × 10¹³ cfu ml⁻¹ Rs-198) per grapevine treatment (BFP3) were 17.2%, 6.2%, and 4.4% higher than those of CK (control, non-inoculation) treatment, respectively. The available phosphorus contents in addition with 40 ml Rs198LBF per grapevine (BFP2) and BFP3 treatments were 12.6% and 55.3% higher than those of CK treatment (P < 0.05). The activities of invertase and alkaline phosphatase were improved in BFP2 and BFP3 treatment compared with those in CK. The relative abundance of potentially beneficial bacteria significantly increased compared with that in CK treatment (P < 0.05). The clusters of orthologous groups (COG) annotation illustrated that the application of 60 ml Rs198LBF increased the relative abundance of metabolic genes in rhizosphere soil. The results of this study show that biofertilizer is very effective in enhancing plant growth and affects soil community diversity.

Extracts of Common Pesticidal Plants Increase Plant Growth and Yield in Common Bean Plants

Common bean (Phaseolus vulgaris) is an important food and cash crop in many countries. Bean crop yields in sub-Saharan Africa are on average 50% lower than the global average, which is largely due to severe problems with pests and diseases as well as poor soil fertility exacerbated by low-input smallholder production systems. Recent on-farm research in eastern Africa has shown that commonly available plants with pesticidal properties can successfully manage arthropod pests. However, reducing common bean yield gaps still requires further sustainable solutions to other crop provisioning services such as soil fertility and plant nutrition. Smallholder farmers using pesticidal plants have claimed that the application of pesticidal plant extracts boosts plant growth, potentially through working as a foliar fertiliser. Thus, the aims of the research presented here were to determine whether plant growth and yield could be enhanced and which metabolic processes were induced through the application of plant extracts commonly used for pest control in eastern Africa. Extracts from Tephrosia vogelii and Tithonia diversifolia were prepared at a concentration of 10% w/v and applied to potted bean plants in a pest-free screen house as foliar sprays as well as directly to the soil around bean plants to evaluate their contribution to growth, yield and potential changes in primary or secondary metabolites. Outcomes of this study showed that the plant extracts significantly increased chlorophyll content, the number of pods per plant and overall seed yield. Other increases in metabolites were observed, including of rutin, phenylalanine and tryptophan. The plant extracts had a similar effect to a commercially available foliar fertiliser whilst the application as a foliar spray was better than applying the extract to the soil. These results suggest that pesticidal plant extracts can help overcome multiple limitations in crop provisioning services, enhancing plant nutrition in addition to their established uses for crop pest management.

A novel trehalosamine isolated from Bacillus amyloliquefaciens and its antibacterial activities

Bacillus amyloliquefaciens has been widely used as a probiotic in the field of biological control,and its antibacterial compounds plays an important role in the prevention and control of plant, livestock and poultry diseases. It has the advantages of green, safe and efficiency. This study aims to separate and purify active ingredient from Bacillus amyloliquefaciens GN59 and study its antibacterial activity. A novel compound was isolated from GN59 by column chromatography on silica gel and HPLC purification. The chemical structure was identified as α-D-glucopyranosyl-(1 → 1')-3'-amino-3'-deoxy-β-D-glucopyranoside (a,β-3-trehalosamine) on the basis of spectroscopic analysis. This is the first report about a,β-3-trehalosamine isolated from biological resources on an antibiotic activity against pathogenic bacterium. The 3'-neotrehalosamine displayed antibacterial activity across a broad spectrum of microorganisms, including different gram-positive and gram-negative bacteria, with minimal inhibitory concentration (MIC) values ranging from 0.5 to 0.7 mg/mL. The results indicated that the 3'-neotrehalosamine from GN59 might be a potential candidate for bactericide.

Mechanisms of High Concentration Valine-Mediated Inhibition of Peach Tree Shoot Growth

The vigorous growth of the new shoots of the peach tree was not beneficial to high quality and efficient cultivation. High concentration of amino acids can inhibit plant growth, but the mechanism is not clear. In this study, we explored the regulatory effects of seven amino acids (phenylalanine, valine, leucine, isoleucine, serine, D-alanine, and proline) (10 g⋅L^-1) on the growth of peach trees. The results showed that phenylalanine, valine, and proline inhibited peach seedling growth and valine has the most significant effect and it can promote the root growth of peach seedlings. Compared with paclobutrazol, valine treatment improves net photosynthetic rate and fruit quality without reducing shoot diameter or puncture strength, and it does not affect leaf morphology. Valine enhanced the expression of PpSnRK1 (sucrose non-fermenting-1-related protein kinase) and inhibited the expression of PpTOR (Target of Rapamycin) and PpS6K (Ribosomal S6 kinase). The gibberellin content was significantly reduced in the valine treatment group. The endogenous valine content of peach seedlings was increased, acetohydroxyacid synthase (AHAS, E.C. 2.2.1.6) activity was inhibited by feedback, isoleucine synthesis was decreased, the relative amounts of branched chain amino acids were unbalanced, and growth was inhibited. However, isoleucine spraying after valine treatment could increase the content of isoleucine and alleviate the inhibition of valine on the shoot growth. In conclusion, valine is environmentally friendly to inhibit the growth of new shoots of peach trees by regulating the balance of PpSnRK1 and PpTOR and the synthesis of isoleucine.