Special Issue "Biostimulants as Physiological Modulators of Crop Performance and Product Quality"

A special issue of Agronomy (ISSN 2073-4395). This special issue belongs to the section "Horticultural and Floricultural Crops".

Deadline for manuscript submissions: 31 December 2021.

Special Issue Editors

Prof. Dr. Youssef Rouphael
E-Mail Website
Guest Editor
Department of Agricultural Sciences, University of Naples Federico II, 80055 Portici, Italy
Interests: greenhouse crops; vegetables production; hydroponics and aquaponics; plant nutrition; microgreens; sprouts; edible flowers; functional foods, grafting; microbial and non-microbial biostimulants; biofortification; vegetable quality related to preharvest factors; LED; urban agriculture; organic farming
Special Issues and Collections in MDPI journals
Prof. Dr. Giuseppe Colla
E-Mail Website
Guest Editor
Department of Agriculture and Forest Sciences, University of Tuscia, 01100 Viterbo, Italy
Interests: microgreens, sprouts; functional food; crop production; plant nutrition; fertilizers; organic farming; organic agriculture; nutrient management; biofertilizers; vegetable production; fruit quality; fertigation; hydroponics; vegetable crops; biofortification
Special Issues and Collections in MDPI journals

Special Issue Information

Dear Colleagues,

The world’s horticultural systems face a great balancing act between two needs, on one side to raise the supply of food produced on the available farmland, since the global population will increase to more than 10 billion by 2050, and on the other side to reduce agriculture’s impact on the environment and human health. Meeting these two targets presents a major sustainability challenge to scientists and producers, which might be fostered by using natural products known as plant biostimulants. A plant biostimulant has recently been defined in the regulations (EU) 2019/1009 of the European Parliament and Council (EC) as an “EU fertilising product able to stimulate plant nutrition processes independently of the product’s nutrient content with the sole aim of improving one or more of the following characteristics of the plant or the plant rhizosphere: 1) nutrient use efficiency, 2) tolerance to abiotic stress, 3) quality traits, or 4) availability of confined nutrients in the soil or rhizosphere”. Plant biostimulants, by this definition, include several substances with bioactive properties: seaweed and plant extracts, humic and fulvic acids, protein hydrolysates and silicon, as well as some-plant growth-promoting microorganisms: mycorrhizal fungi and plant-growth-promoting rhizobacteria.

Following the huge success of the first Special Issue, “Toward a Sustainable Agriculture Through Plant Biostimulants: From Experimental Data to Practical Applications”, we have decided to launch a second Special Issue entitled “Biostimulants as Physiological Modulators of Crop Performance and Product Quality”. This Special Issue invites original research, technology report, methods, opinion, perspectives, and invited reviews and mini reviews dissecting the biostimulation action of these natural compounds and substances and beneficial microorganisms on crops grown under optimal and suboptimal growing conditions (e.g., salinity, drought, nutrient deficiency and toxicity, heavy metal contaminations, waterlogging, and adverse soil pH conditions). Also of interest are potential contributions dealing with the effect as well as the molecular and physiological mechanisms of plant biostimulants on nutrient efficiency, product quality, post-harvest, and the modulation of the microbial population quantitatively and qualitatively. In addition, identification and understanding of the optimal method, time, rate of application, and phenological stage for improving plant performance and resilience to stress as well as the best plant species/cultivar × environment × management practices combinations will be considered within the general scope of the Special Issue. We strongly believe that this compilation of high-standard scientific papers on principles and practices of plant biostimulants will foster knowledge transfer among scientific communities, industries, and agronomists and will enable a better understanding of the mode of action and application procedure of biostimulants in different cropping systems.

Prof. Youssef Rouphael
Prof. Giuseppe Colla
Guest Editors

Manuscript Submission Information

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Keywords

  • humic acids
  • microbial inoculants
  • PGPR
  • nitrogen-fixing bacteria
  • mycorrhizal fungi
  • microbiome
  • protein hydrolysate
  • silicon
  • physiological and molecular mechanisms
  • seaweed extracts
  • microalgae
  • functional biostimulants
  • agronomical and horticultural crops
  • abiotic stressors
  • NUE
  • post-harvest

Published Papers (16 papers)

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Research

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Article
Biostimulant Effects of Cerium on Seed Germination and Initial Growth of Tomato Seedlings
Agronomy 2021, 11(8), 1525; https://doi.org/10.3390/agronomy11081525 - 30 Jul 2021
Viewed by 151
Abstract
The rare earth element (REE) cerium (Ce) can act as a biostimulant in diverse crop plants. The effects of 0, 5, 10, and 15 µM Ce (supplied as CeCl3 7H2O) on seed germination and the initial growth of tomato ( [...] Read more.
The rare earth element (REE) cerium (Ce) can act as a biostimulant in diverse crop plants. The effects of 0, 5, 10, and 15 µM Ce (supplied as CeCl3 7H2O) on seed germination and the initial growth of tomato (Solanum lycopersicum L.) cv. Vengador were evaluated. After a 12 h imbibition, the weight of the seeds treated with 15 µM Ce was 37.5% greater than that observed in the control. The germination index of the seeds treated with 5 µM Ce was greater than 100% (101.93%), though when applying 10 µM Ce this index was 17.53% lower than the control seeds. Nevertheless, Ce treatments did not significantly affect the coefficient of velocity of germination, relative seed germination, germination index, radicle length, dry biomass, or relative growth. Interestingly, shoot length increased significantly in the treatments with 5, 10, and 15 µM Ce. This tendency was also observed in the dry biomass weight and relative growth of the shoots. Hence, Ce has a stimulating effect on germination and initial growth in tomato cv. Vengador shoots. In particular, there was a priming effect of Ce on seeds, reflected in a higher weight gain in Ce-treated seeds, which indicated greater water absorption. Therefore, Ce can be an alternative to accelerate the production time of tomato seedlings in seedbeds. Full article
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Article
The Modulation of Auxin-Responsive Genes, Phytohormone Profile, and Metabolomic Signature in Leaves of Tomato Cuttings Is Specifically Modulated by Different Protein Hydrolysates
Agronomy 2021, 11(8), 1524; https://doi.org/10.3390/agronomy11081524 - 30 Jul 2021
Viewed by 163
Abstract
Protein hydrolysates (PHs) are employed in agriculture to increase the sustainability of farming systems, with positive results on crop productivity and response against environmental stressors. Nevertheless, the molecular mechanism(s) triggered by their specific activity is not clearly understood. In this work, five PHs [...] Read more.
Protein hydrolysates (PHs) are employed in agriculture to increase the sustainability of farming systems, with positive results on crop productivity and response against environmental stressors. Nevertheless, the molecular mechanism(s) triggered by their specific activity is not clearly understood. In this work, five PHs obtained by enzymatic hydrolysis of different vegetal protein sources were tested for their root-promoting activity on tomato cuttings. All the treatments improved both root length and number when compared to negative controls. Distinctive metabolomic signatures were highlighted in response to treatments, indicating the triggering of different molecular processes in leaf tissues of tomato cuttings. PHs differentially modulated the biosynthesis of plant stress-protectants, such as alkaloids and phenylpropanoids. Moreover, metabolites involved in phytohormone biosynthesis were significantly impacted. In this context, a clear modulation of several compounds related to auxin homeostasis was observed. In addition, the differential modulation of SlIAA2 and SlIAA9 genes, which are involved in the IAA signalling pathway, might further suggest the auxin-like activity elicited by the PHs tested. Here we provide evidence that PHs can impact plant molecular level, positively affecting root development, most likely by affecting the signalling cascades activated in leaf tissues. The biostimulant activity was sustained by PH-specific response at the molecular level, likely ascribable to their heterogeneous botanical origins. In fact, our findings did not point out a clear universal response to PHs, and specific effects are to be investigated. Full article
Article
Foliar and Root Applications of Vegetal-Derived Protein Hydrolysates Differentially Enhance the Yield and Qualitative Attributes of Two Lettuce Cultivars Grown in Floating System
Agronomy 2021, 11(6), 1194; https://doi.org/10.3390/agronomy11061194 - 11 Jun 2021
Cited by 1 | Viewed by 421
Abstract
Lettuce (Lactuca sativa L.) is a leafy vegetable cultivated widely for its fast and year-round production and its beneficial phytochemical content, which may be boosted further by plant biostimulants that are considered eco-sustainable means for enhancing horticultural crop production. A greenhouse experiment [...] Read more.
Lettuce (Lactuca sativa L.) is a leafy vegetable cultivated widely for its fast and year-round production and its beneficial phytochemical content, which may be boosted further by plant biostimulants that are considered eco-sustainable means for enhancing horticultural crop production. A greenhouse experiment was carried out to evaluate the yield and qualitative parameters of two differently pigmented lettuce cultivars grown in a floating raft system either untreated or treated (leaf, root or leaf/root application) with vegetal protein hydrolysates (PHs). For foliar application (F), lettuce plants were sprayed at a dose of 3 mL L−1, whereas for root application, 0.15 (T1) or 0.3 (T2) mL L−1 was applied to the nutrient solution alone or in combination with foliar spray (T1 + F and T2 + F) with the same foliar concentration. Bio-morphometric and production data were collected after harvest. Physiological and plant nutrition assays included leaf gas exchange, leaf fluorescence, SPAD index, mineral content, carotenoids, total phenols, total ascorbic acid content and antioxidant activities. Cultivar-specific reactions to biostimulant application were noted: whilst the green pigmented cultivar thrived under nutrient solution applications and recorded higher yield by 82.7% (T1) or (T1 + F) and 71.7% (T2), the red cultivar thrived under combined treatments, yielding 55.4% (T2 + F) higher than control and providing the most concentrated phytochemical content. These latter treatments also engendered the highest SPAD index, Fv/Fm ratio, CO2 assimilation, stomatal conductance and transpiration. In addition, the T2 + F treatment boosted ‘Canasta’ hydrophilic antioxidant activity (21.9%) and total ascorbic acid (5.6-fold). Nutrient solution treatments alone proved advantageous when compared to foliar treatments, while mixed treatments proved genotype-specific. New research on genotype specificity of biostimulant effects is warranted for future use, in order to rationalize biostimulant application modes and dosages. Full article
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Article
VNT4, a Derived Formulation of Glutacetine® Biostimulant, Improved Yield and N-Related Traits of Bread Wheat When Mixed with Urea-Ammonium-Nitrate Solution
Agronomy 2021, 11(5), 1013; https://doi.org/10.3390/agronomy11051013 - 20 May 2021
Viewed by 471
Abstract
Optimizing nitrogen use efficiency (NUE) could mitigate the adverse effects of nitrogen (N) fertilizers by limiting their environmental risks and raising agronomic performance. We studied the effects of VNT4, a derived formulation of Glutacetine® biostimulant, mixed with urea-ammonium-nitrate solution (UAN) on the [...] Read more.
Optimizing nitrogen use efficiency (NUE) could mitigate the adverse effects of nitrogen (N) fertilizers by limiting their environmental risks and raising agronomic performance. We studied the effects of VNT4, a derived formulation of Glutacetine® biostimulant, mixed with urea-ammonium-nitrate solution (UAN) on the growth, N-related traits and agronomic performance of winter wheat (Triticum aestivum L.). The experiment was performed under six contrasting field conditions over two years in Normandy (France), including a site where 15N labelling was undertaken. Taking into account all the sites, we report that VNT4 significantly improved grain yield (+359 kg ha−1), total grain N and NUE. VNT4 application improved growth during tillering and stem elongation (+10.7%), and N and 15N uptake between tillering and maturity (+7.3% N and +16.9% 15N) leading to a higher N accumulation at maturity (+9.3% N). This N mainly originated from fertilizer (+19.4% 15N) and was assimilated after the flag leaf stage in particular (+47.6% 15N). These effects could be related to maintenance of physiological functions of flag leaves as suggested by the enhancement of their nutrient status (especially S, Zn and Mo). The adoption of VNT4 as a UAN additive is an efficient agronomic practice to enhance wheat productivity under an oceanic temperate climate. Full article
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Article
Transcriptomic and Metabolomic Studies Reveal Mechanisms of Effects of CPPU-Mediated Fruit-Setting on Attenuating Volatile Attributes of Melon Fruit
Agronomy 2021, 11(5), 1007; https://doi.org/10.3390/agronomy11051007 - 19 May 2021
Viewed by 478
Abstract
N1-(2-chloro-4-pyridyl)-N3-phenylurea (CPPU), a synthetic cytokinin-active compound, is widely applied to induce parthenocarpic fruit set and enhance melon fruit enlargement (Cucumis melo L.). CPPU may also influence fruit quality; however, the mechanisms through which this occurs remain unknown. We investigated the differences in [...] Read more.
N1-(2-chloro-4-pyridyl)-N3-phenylurea (CPPU), a synthetic cytokinin-active compound, is widely applied to induce parthenocarpic fruit set and enhance melon fruit enlargement (Cucumis melo L.). CPPU may also influence fruit quality; however, the mechanisms through which this occurs remain unknown. We investigated the differences in volatile emissions between parthenocarpic fruit set by CPPU (C) and seeded fruit set by artificial pollination (P). Gas chromatography–mass spectrometry (GC–MS) analysis revealed that six volatile organic compounds (VOCs) emitted by the P-group fruits were not detected in C-group fruits. The relative abundances of another 14 VOCs emitted by the CPPU-treated fruits were less than those in the P-group fruits. RNA sequencing analysis indicated that a total of 1027, 994, and 743 differentially expressed genes (DEGs) were detected in the C20 (treatment with 20 mg·L–1 CPPU) vs. P, P-C20 (pollination followed by 20 mg·L−1 CPPU treatment) vs. P, and P-C20 vs. C20 treatments, respectively. Compared with the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases, the DEGs related to fatty acid degradation and metabolism, which contribute to volatile production, were enriched. In particular, DEGs such as carotenoid cleavage dioxygenase (CCD)-, lipoxygenase (LOX)-, alcohol dehydrogenase (ADH)-, and alcohol acyltransferase (ATT)-related genes were closely related to the formation of volatiles. In summary, our study provides a metabolic and transcriptomic atlas, reveals the impact of CPPU on VOCs, and enhances our understanding of the mechanisms of CPPU that contribute towards generally reducing the quality of melon fruit. Full article
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Article
Biostimulant Application Improves Yield Parameters and Accentuates Fruit Color of Annurca Apples
Agronomy 2021, 11(4), 715; https://doi.org/10.3390/agronomy11040715 - 09 Apr 2021
Viewed by 513
Abstract
The Annurca apple is a typical fruit from Southern Italy that is notable for its high firmness and characteristic flavor, and presents positive effects on human health. The aim of the present study was to improve the agronomic characteristics of Annurca trees and [...] Read more.
The Annurca apple is a typical fruit from Southern Italy that is notable for its high firmness and characteristic flavor, and presents positive effects on human health. The aim of the present study was to improve the agronomic characteristics of Annurca trees and the quality of their fruits by the use of plant biostimulants. We performed the study with three biostimulants (protein hydrolysates, seaweed extracts, and microalgae) to determine their effects on trees and fruits at harvest and during fridge conservation. The measurements in the field concerned the production per plant, the number of fruits, the diameter and fruit weight, the diameter of trunk, the weight of pruning, the first harvest %, and yield efficiency (plant prod./TCSA) for both growing seasons 2018–2019. The analyzed fruit parameters at harvest and during the fridge conservation were: flesh firmness, epicarp color, total soluble solids, pH, and titratable acidity. The results showed positive effects of the biostimulants on the production and the color parameters, especially with microalgae enhancing fruit redness (5-fold) and color index (8.5-fold). In particular, protein hydrolysates and microalgae increased the production (10.4%), diameter of the fruits (7.0%), the first harvest percentage (37.8%), and yield efficiency (6.9%). The tested plant biostimulants showed no significant effect on the measured qualitative parameters. This study represents the first detailed research on the use of different types of biostimulants on Annurca trees and their impact on the quality of its fruits from harvest to storage, and may present a sustainable alternative for the “melaio” processes. Full article
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Article
Yield Enhancement of Biostimulants, Vitamin B12, and CoQ10 Compared to Inorganic Fertilizer in Radish
Agronomy 2021, 11(4), 697; https://doi.org/10.3390/agronomy11040697 - 07 Apr 2021
Viewed by 532
Abstract
Two pot experiments were conducted to evaluate the response of radish crops against different plant growth regulators, biostimulants, and leaf extracts at Yale University, USA. The first experiment examined the marginal effect of vitamin B12 when added to the Berlyn Laboratory’s proprietary biostimulant [...] Read more.
Two pot experiments were conducted to evaluate the response of radish crops against different plant growth regulators, biostimulants, and leaf extracts at Yale University, USA. The first experiment examined the marginal effect of vitamin B12 when added to the Berlyn Laboratory’s proprietary biostimulant formula (GPB Core). Increasing concentrations of vitamin B12 were added, as investigated in groups SL (0 mg/L), SB1 (0.5 mg/L), SB2 (1.0 mg/L), and SB3 (1.5 mg/L). The addition of vitamin B12 conferred no significant incremental benefit over the GPB Core. However, the GPB Core formula (SL) increased fresh shoot biomass by 172.9%, dry shoot biomass by 136.4%, fresh root biomass by 64.7%, and dry root biomass by 29.1% over plant treated with inorganic fertilizer alone (p < 0.01). The second experiment examined the combined marginal effect of vitamin B12 and coenzyme Q10 (CoQ10) when added to the GPB Core. The three experimental groups included the GPB Core plus inorganic fertilizer (S+); GPB Core, vitamin B12, CoQ10, and inorganic fertilizer (SBQ+); and GPB Core, vitamin B12, CoQ10, and no inorganic fertilizer (SBQ0). SBQ0 outperformed the inorganic fertilizer control in fresh shoot, dry shoot, fresh root, and dry root biomass by 190.3%, 127.1%, 128.5%, and 41.3%, respectively (p < 0.01), indicating that inorganic fertilizer can be replaced by biostimulants while simultaneously increasing yield. Additionally, the differences between SBQ+ and SBQ0 in the biomass metrics were statistically insignificant, indicating that in the presence of biostimulants, inorganic fertilizers confer a slight marginal benefit. There was no evidence, however, that the addition of CoQ10 and vitamin B12 conferred benefits over S+. Overall, the application of biostimulants statistically significantly improves radish biomass. Both experiments indicate that under low stress conditions, biostimulants can replace inorganic fertilizer while simultaneously increasing yield. Full article
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Article
Protein Hydrolysates Supplement in the Nutrient Solution of Soilless Grown Fresh Peppermint and Spearmint as a Tool for Improving Product Quality
Agronomy 2021, 11(2), 317; https://doi.org/10.3390/agronomy11020317 - 11 Feb 2021
Cited by 1 | Viewed by 626
Abstract
The present study investigated the potential of fresh peppermint (Mentha × piperita L.) and spearmint (Menthaspicata L.) production on a floating raft system combined with a commercial protein hydrolysate supplement (Amino16®) in a nutrient solution aiming to improve [...] Read more.
The present study investigated the potential of fresh peppermint (Mentha × piperita L.) and spearmint (Menthaspicata L.) production on a floating raft system combined with a commercial protein hydrolysate supplement (Amino16®) in a nutrient solution aiming to improve plant product quality. Three levels of the protein hydrolysate solution (0, 0.25 and 0.50%) were added in the nutrient solution, and the plants were harvested after twenty-four days. Plant growth characteristics were recorded, and nutritional, essential oil and polyphenolic composition were determined in fresh tissue. The addition of protein hydrolysates did not affect the fresh or dry weight but reduced plant height. Nitrate content significantly decreased, while total chlorophyll and essential oil content increased in both species. Moreover, the protein hydrolysate solution further increased total antioxidant capacity, total soluble phenol and carotenoid contents in spearmint plants, while it did not affect the essential oil and polyphenolic composition in both species. In conclusion, protein hydrolysates solution may be added in the nutrient solution, to improve the quality of peppermint and spearmint grown in a floating system, without adverse effects on crop yield or the essential oil and polyphenolic profile. Full article
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Article
Assessment of the Possibilities of Using Cross-Linked Polyacrylamide (Agro Hydrogel) and Preparations with Biostimulation in Building the Quality Potential of Newly Planted Apple Trees
Agronomy 2021, 11(1), 125; https://doi.org/10.3390/agronomy11010125 - 11 Jan 2021
Viewed by 577
Abstract
The research was carried out in a commercial apple orchard in southeastern Poland. The aim of the research was to evaluate the effect of fertilizer with biostimulation and humic acids with algae extracts and agrogel on the reception and growth of newly planted [...] Read more.
The research was carried out in a commercial apple orchard in southeastern Poland. The aim of the research was to evaluate the effect of fertilizer with biostimulation and humic acids with algae extracts and agrogel on the reception and growth of newly planted maiden apple trees of the ‘Gala Must’ variety. One-year-old budwoods were planted annually on the site where fruit trees had grown for 20 years. For the purpose of the experiment, old trees were grubbed up every year in autumn. The experiment assessed the growth and quality of apple trees in the fall of the first year after planting them permanently using a biostimulator in the form of fertilizer and agrogel. On the basis of 3-year studies, it was shown that the application of the assessed preparations had a positive effect on the quality parameters of the trees. The experiment showed the positive effect of the preparation with biostimulation on the best growth and quality parameters every year, which was confirmed by the multidimensional cluster analysis. The fact that the use of agrogel significantly modified the height of the evaluated apple trees in the second year of the study, when lower amounts of rainfall were recorded, is particularly noteworthy. Full article
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Article
Systematic Investigation of the Effects of a Novel Protein Hydrolysate on the Growth, Physiological Parameters, Fruit Development and Yield of Grapevine (Vitis Vinifera L., cv Sauvignon Blanc) under Water Stress Conditions
Agronomy 2020, 10(11), 1785; https://doi.org/10.3390/agronomy10111785 - 14 Nov 2020
Cited by 2 | Viewed by 573
Abstract
In the last decade climate change has impacted viticulture and water deficit has become a major concern in fruit production. Many studies have been carried out to determine the grapevine response to environmental changes and to identify key genetic traits to be used [...] Read more.
In the last decade climate change has impacted viticulture and water deficit has become a major concern in fruit production. Many studies have been carried out to determine the grapevine response to environmental changes and to identify key genetic traits to be used in grapevine breeding. However, in order to better manage climate-related risks, novel viticultural practices are urgently needed. A promising solution for a more sustainable model of viticulture involves the use of biostimulants. In this study, the effectiveness of a novel biostimulant (APR®) belonging to the group of protein thermal hydrolysates was tested on grapevine plants subjected to progressive water deficit conditions. Our results showed that this compound applied to roots before imposing water deprivation mitigates the consequences of stress by sustaining the growth of the younger vegetative organs and limiting the extent of cell dehydration; this positive impact on the plant’s physiological state persisted during the recovery phase. Furthermore, at the end of the growing season, plants treated with the biostimulant, both in optimal water conditions and under water stress, exhibited a greater accumulation of biomass in the aerial part (6.8% and 21.3 %, respectively) and a higher berry diameter (3.4 % and 9.5 %, respectively). Additional work through field trials will be necessary to further substantiate these results and to translate this knowledge into specific practices that grape growers can easily adopt. Full article
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Article
Modification of Yield and Fiber Fractions Biosynthesis in Phaseolus vulgaris L. by Treatment with Biostimulants Containing Amino Acids and Seaweed Extract
Agronomy 2020, 10(9), 1338; https://doi.org/10.3390/agronomy10091338 - 05 Sep 2020
Cited by 3 | Viewed by 843
Abstract
The most serious of these is to stimulate the development of sustainable and, at the same time, environmentally friendly systems. Therefore, this study aimed to determine the effect of two biostimulants on the bean yield and fiber fractions in seeds: neutral-detergent fiber, acid-detergent [...] Read more.
The most serious of these is to stimulate the development of sustainable and, at the same time, environmentally friendly systems. Therefore, this study aimed to determine the effect of two biostimulants on the bean yield and fiber fractions in seeds: neutral-detergent fiber, acid-detergent fiber, lignin, cellulose, and hemicellulose. The field experiment performed in 2016–2018 in Poland. Over the growing season, plants were treated with biostimulants seaweed extracts (concentrations of 0.7% and 1%) and amino acids (0.3% and 0.5%) based products. Plants were sprayed a single time in the Biologische Bundesanstalt, Bundessortenamt and Chemical industry (BBCH) 13–15 phenological phases and a double spray in the BBCH 13–15 and 61. The study showed a significant increase in bean yield (average 32.08% compare to control) when seaweed extracts was used in the form of a double spray at a higher concentration. In the case of the application of amino acids-based product, the best results (increase of 21.97%) were obtained using a double spray at a lower concentration. It was found that the tested biostimulants changed the fiber fractions of bean seeds. The acid-detergent fiber (ADF) content was the highest (average increase of 2%) after double plant treatment with seaweed extracts based product. While the increased concentration of neutral-detergent fiber (NDF) (over 4%) resulted from double spraying with lower concentration of this biostimulant. The increase in the lignin (ADL) (1.12%), hemicellulose (HCEL) (4.54%), and cellulose (CEL) (0.91%) represented plant response to the double application of this biostimulant in the higher concentration. The results indicated also that the use of amino acids-based product caused an increase in the ADF (0.28%), NDF (10.27%), ADL (0.63%), and HCEL (9.99%) contents in bean seeds as an effect of double plant treatment with this biostimulant at lower concentration. Full article
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Article
Effect of Biostimulants on Apple Quality at Harvest and After Storage
Agronomy 2020, 10(8), 1214; https://doi.org/10.3390/agronomy10081214 - 18 Aug 2020
Cited by 2 | Viewed by 1224
Abstract
Nutritional unbalances, such as calcium deficiency at the fruit level, are generally the causative agent of post-harvest disorders in apples. Foliar application of Ca as calcium chloride is the current solution to increase Ca concentration in apples, even though the effectiveness of this [...] Read more.
Nutritional unbalances, such as calcium deficiency at the fruit level, are generally the causative agent of post-harvest disorders in apples. Foliar application of Ca as calcium chloride is the current solution to increase Ca concentration in apples, even though the effectiveness of this approach is often not satisfactory. In this research, we tested the efficacy of a combined application of Ca with selected biostimulants to improve apple quality and to reduce the incidence of storage disorders. The experiment was conducted in two “Jonathan” apple orchards that differed in management systems and characteristics. Tree canopies were sprayed with calcium chloride alone and in combination with a commercial product containing zinc and silicon or a seaweed extract. The seaweed extract increased apple quality by boosting the reddish coloration (+32% of color index) and by enhancing final anthocyanin concentration of fruit skin. Both biostimulants significantly reduced (by 20%) the incidence of the physiological disorder, known as “Jonathan spot”, after 160 days of storage. Increased concentration of nutrients (Ca, Zn, and Mn) in the skin of apples after biostimulant applications, together with changes of the phenolic profile during the storage, are discussed as the possible causes of the reduced fruit susceptibility to post-harvest disorders. Full article
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Article
Impact of New Micro Carbon Technology Based Fertilizers on Growth, Nutrient Efficiency and Root Cell Morphology of Capsicum annuum L.
Agronomy 2020, 10(8), 1165; https://doi.org/10.3390/agronomy10081165 - 08 Aug 2020
Cited by 1 | Viewed by 768
Abstract
The aim of this study was to determine the effects of new Micro Carbon Technology (MCT®) fertilizers based on humic acids biologically digested on the growth and development of pepper plants. In this work, the biostimulant effect of MCT® fertilizers [...] Read more.
The aim of this study was to determine the effects of new Micro Carbon Technology (MCT®) fertilizers based on humic acids biologically digested on the growth and development of pepper plants. In this work, the biostimulant effect of MCT® fertilizers was compared to conventional mineral fertilizers. In order to evaluate MCT® fertilizers, a previous chemical characterization (infrared spectroscopy, liquid chromatography and mass spectrometry) of seven MCT® fertilizers was performed. Two fertilization tests of pepper plants were carried out in hydroponic conditions, where the fertilization and the age of the plants were studied in order to evaluate the specific effects on roots and leaves. Plant weight and foliar analysis (chlorophyll indices and nutrients) have been determined. Transmission electron microscopy was used to visualize the morphological differences in the root and leaf cells. Comparison between conventional and MCT® based fertilizers showed that, with the MCT® fertilizers, the plant is exposed to the presence of free amino acids (Glycine and Alanine), polyphenols and humic substances. Although no significant differences were found in plant mass production, the plants fertilized with MCT® products presented better nutritional status than plants treated with conventional fertilization in terms of nutrient content in leaves. Important morphological differences in root cells were found. A large central vacuole that represented the 68–83% of the total root cell area was shown if the MCT® products were used, suggesting significant changes of membrane permeability in terms of water adsorption and consequently nutrient storage. The morphological differences observed in the root cells were more noticeable in adult plants. Full article
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Article
Effect of Reduced Nitrogen and Supplemented Amino Acids Nutrient Solution on the Nutritional Quality of Baby Green and Red Lettuce Grown in a Floating System
Agronomy 2020, 10(7), 922; https://doi.org/10.3390/agronomy10070922 - 27 Jun 2020
Cited by 7 | Viewed by 749
Abstract
Excessive nitrogen fertilization results in nitrate accumulation in leafy vegetables. Reducing the dose of mineral nitrogen or using alternate fertilizers lowers the nitrate accumulation; however, a critical minimum level of mineral nitrogen is necessary to maintain yield and nutritional quality. The aim of [...] Read more.
Excessive nitrogen fertilization results in nitrate accumulation in leafy vegetables. Reducing the dose of mineral nitrogen or using alternate fertilizers lowers the nitrate accumulation; however, a critical minimum level of mineral nitrogen is necessary to maintain yield and nutritional quality. The aim of this study was to evaluate the effect of two levels of mineral nitrogen (100% and 50%) and three levels of an amino acid solution (0, 0.3, and 0.9%) in the nutrient solution of two baby lettuce cultivars (green and red) grown in a floating system. Nitrogen reduction did not affect yield (12.9–13.4 and 11.0–11.3 g/plant, respectively) but reduced nitrate accumulation (by 43 and 19%, respectively) in both green and red lettuce, while enhancing phenolic content (by 28%) and antioxidant capacity (by 69%) in green lettuce and soluble solid (by 7%) and total chlorophyll content (by 9%) in red lettuce. Although nitrate accumulation was prevented (< 355 mg/kg FW) and most nutritional components increased in both lettuce types by amino acids supplementation, plant growth was negatively affected, especially in red lettuce, in both concentrations of amino acids (reduction by 9 and 35% in 0.3 and 0.9%, respectively). In both lettuce types, proline content increased by 0.9% amino acids supplementation (by 45%), implying a probable induction of a stress condition. Mineral nutrients were slightly affected by nitrogen reduction, which was probably perceived as an abiotic stress. Full article
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Review

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Review
Plant Biostimulants: A Categorical Review, Their Implications for Row Crop Production, and Relation to Soil Health Indicators
Agronomy 2021, 11(7), 1297; https://doi.org/10.3390/agronomy11071297 - 26 Jun 2021
Viewed by 1144
Abstract
Plant biostimulants are specialty products used to increase crop production and are quickly becoming common in the agricultural seed and chemical marketplace. Unlike traditional crop inputs, such as fertilizers or pesticides, biostimulants are unique in that a single product may have multiple avenues [...] Read more.
Plant biostimulants are specialty products used to increase crop production and are quickly becoming common in the agricultural seed and chemical marketplace. Unlike traditional crop inputs, such as fertilizers or pesticides, biostimulants are unique in that a single product may have multiple avenues for influencing crop growth and development based on both the timing and the placement of application. This review presents a summary of the current status and descriptions of plant biostimulants with available literature on their uses in the row crop production of maize (Zea mays L.), soybean (Glycine max (L.) Merr.), wheat (Triticum aestivum), and other major crop species. Biostimulants have much potential to improve crop production through enhanced yields, grain quality, and increased sustainability of agronomic production systems, particularly in relation to nutrient management. However, there is great variability in the efficacy of biostimulants and a limited understanding of the mechanisms responsible in field-tested scenarios where differences are observed. These unknown mechanisms may align with the recognized soil health indicators, providing opportunities for unrealized biostimulant potential beyond crop growth and development. This review aims to identify the predominant types of crop biostimulants, the known understandings of their modes of action, and examples of their current field efficacy with an outlook for their future. Full article
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Review
Health-Promoting Properties of Plant Products: The Role of Mycorrhizal Fungi and Associated Bacteria
Agronomy 2020, 10(12), 1864; https://doi.org/10.3390/agronomy10121864 - 26 Nov 2020
Cited by 1 | Viewed by 680
Abstract
The concept of food quality, traditionally based on nutritional and sensory properties, has recently acquired an additional meaning, referring to the health-promoting properties of plant products, that are ascribed to plant secondary metabolites called phytochemicals, primarily represented by polyphenolic compounds and glucosinolates. The [...] Read more.
The concept of food quality, traditionally based on nutritional and sensory properties, has recently acquired an additional meaning, referring to the health-promoting properties of plant products, that are ascribed to plant secondary metabolites called phytochemicals, primarily represented by polyphenolic compounds and glucosinolates. The diversity and content of phytochemicals in plant products are affected by different variables, such as plant genotype, agronomic factors, and arbuscular mycorrhizal fungi (AMF), which establish mycorrhizal symbioses with most crops, including cereals, legumes, vegetables, fruit trees, sunflower, cotton, and sugarcane. AMF and associated bacteria enhance plant growth and health, and affect the production of polyphenols and carotenoids, and the activity of antioxidant enzymes. The production of health-promoting phytochemicals was shown to be differentially modulated by different AMF isolates and bacterial strains, in several food plants, i.e., tomato, lettuce, strawberry, artichoke, maize, grapevine, sunflower. Here, we provide an overview of recent studies concerning the multiple roles played by AMF and associated bacteria in the modulation of the biosynthesis of plant secondary metabolites with health-promoting activity, and discuss the development of designed multifunctional consortia to be used in sustainable agriculture. Full article
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: Innovative Trichoderma spp. - fatty acid formulations with enhanced biocontrol activity and effectiveness in the improvement horticultural crop yield and nutritional quality
Authors: S. Lanzuise1 †, G. Manganiello1,2 †, V. Guastaferro1, C. Vincenzo1, P. Vitaglione1, L. Ferracane1, A. Vecchi3, F. Vinale6,7, S.L. Woo4,5,6, M. Lorito1,5,6
Affiliation: 1 Department of Agricultural Sciences, University of Naples Federico II, 80055 Portici, Italy 2 Consiglio per la Ricerca in Agricoltura e l'Analisi dell'Economia Agraria, Centro di Ricerca Orticoltura e Florovivaismo, Pontecagnano Faiano, Italy 3 Alpha Biopesticides, Cowley Road, Cambridge, CB4 0WS, United Kingdom 4 Department of Pharmacy, University of Naples Federico II, 80131 Naples, Italy 5 Task Force on Microbiome Studies, University of Naples Federico II, 80055 Portici, Italy 6 National Research Council, Institute for Sustainable Plant Protection, 80055 Portici, Italy 7 Department of Veterinary Medicine and Animal Productions, University of Naples Federico II, 80137 Naples, Italy † These authors contributed equally to this work.
Abstract: Intensive agricultural practices may severely affect wildlife habitats by contributing to increased levels of environmental pollution that generate serious risks to human health. The growing demand for safer and sustainable food products reflects the public awareness about the adverse consequences of the chemical applications used in agriculture production. For this reason, research is focusing on the development of innovative and eco-friendly approaches for enhancing crop yields, quality and protection. The application of biological control agents (BCAs) represents one of the most promising non-chemical strategies for defending plants from pathogen and pest attack. The aims of the current work were to investigate and develop new biological formulations based on the combination of a microbial consortium containing two different Trichoderma spp., with a mixture of medium and long chain (C14-C18) fatty acids (FAm), for applications as biofungicides and plant biostimulants. The biological activity of these new formulations on different vegetable crops (tomato, lettuce, kohlrabi) was evaluated in terms of disease control, plant productivity and properties. An untargeted metabolomic analysis was carried out by LC-MS to investigate how the formulation components modulate secondary metabolite production in tomato. Results demonstrated that Trichoderma spp.-FAm combinations were effective in containing the soil-borne pathogen Rhizoctonia solani on tomato and lettuce plants. Furthermore, plants exhibited a growth promotion effect with the treatments that resulted in increased yields and a significant enrichment of plant compounds in terms of carotenoids in tomato, polyphenols in lettuce and glucosinolates in kohlrabi. The current research highlights the possibility of developing new bio-formulations that increase crop performance in terms of disease control, growth promotion, yield increase and nutritional properties, in a perspective of a sustainable agriculture.

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