Biostimulants as an Alternative to Improve the Wine Quality from Vitis vinifera (cv. Tempranillo) in La Rioja

Effects of foliar applications of γ-polyglutamic acid and alginic acid on the quality and antioxidant activity of Marselan grapes and wines

This study investigated the effects of γ-polyglutamic acid (PGA) and alginic acid (ALA) on grapes and wines. Marselan grapes were utilized to assess the accumulation and synthesis of phenolic compounds and antioxidant activity. The 0.35 % (v/v) PGA (PGA2) significantly enhanced the antioxidant activity of both grapes and wines in both years. Overall, treatments with 0.45 % (v/v) PGA (PGA3), 0.45 % (v/v) ALA (ALA3), and 0.25 % (v/v) ALA (ALA1) notably increased the total phenolic and anthocyanin content in both grapes and wines. Among these, PGA3 treatment significantly upregulated the levels of Delphinidin-3-O-(6-acetyl)-glucoside, Cyanidin-3-O-(6-acetyl)-glucoside, Peonidin-3-O-glucoside, and Malvidin-3-O-(trans-6-O-coumaryl)-glucoside in both years. Additionally, PGA3 treatment elevated the expression of the VvPAL, VvCHS, VvDFR and VvLDOX genes across both years. In contrast, ALA3 and ALA1 treatments increased anthocyanin content by upregulating the expression of VvCHS, VvF3'H and VvUFGT genes. In summary, PGA3 treatment significantly enhanced the phenolic compounds and antioxidant activity in both grapes and wines. These findings demonstrate the potential of PGA and ALA as biostimulants to significantly enhance grape and wine quality in viticulture.

Metabolic Processes and Biological Macromolecules Defined the Positive Effects of Protein-Rich Biostimulants on Sugar Beet Plant Development

Protein-based biostimulants (PBBs) have a positive effect on plant development, although the biological background for this effect is not well understood. Here, hydrolyzed wheat gluten (HWG) and potato protein film (PF) in two levels (1 and 2 g/kg soil) and in two different soils (low and high nutrient; LNC and HNC) were used as PBBs. The effect of these PBBs on agronomic traits, sugars, protein, and peptides, as well as metabolic processes, were evaluated on sugar beet in comparison with no treatment (control) and treatment with nutrient solution (NS). The results showed a significant growth enhancement of the plants using HWG and PF across the two soils. Sucrose and total sugar content in the roots were high in NS-treated plants and correlated to root growth in HNC soil. Traits related to protein composition, including nitrogen, peptide, and RuBisCO contents, were enhanced in PBB-treated plants (mostly for HWG and PF at 2 g/kg soil) by 100% and >250% in HNC and LNC, respectively, compared to control. The transcriptomic analysis revealed that genes associated with ribosomes and photosynthesis were upregulated in the leaf samples of plants treated with either HWG or PP compared to the control. Furthermore, genes associated with the biosynthesis of secondary metabolites were largely down-regulated in root samples of HWG or PF-treated plants. Thus, the PBBs enhanced protein-related traits in the plants through a higher transcription rate of genes related to protein- and photosynthesis, which resulted in increased plant growth, especially when added in certain amounts (2 g/kg soil). However, sucrose accumulation in the roots of sugar beet seemed to be related to the easy availability of nitrogen.

Application of biostimulant products and biological control agents in sustainable viticulture: A review

Current and continuing climate change in the Anthropocene epoch requires sustainable agricultural practices. Additionally, due to changing consumer preferences, organic approaches to cultivation are gaining popularity. The global market for organic grapes, grape products, and wine is growing. Biostimulant and biocontrol products are often applied in organic vineyards and can reduce the synthetic fertilizer, pesticide, and fungicide requirements of a vineyard. Plant growth promotion following application is also observed under a variety of challenging conditions associated with global warming. This paper reviews different groups of biostimulants and their effects on viticulture, including microorganisms, protein hydrolysates, humic acids, pyrogenic materials, and seaweed extracts. Of special interest are biostimulants with utility in protecting plants against the effects of climate change, including drought and heat stress. While many beneficial effects have been reported following the application of these materials, most studies lack a mechanistic explanation, and important parameters are often undefined (e.g., soil characteristics and nutrient availability). We recommend an increased study of the underlying mechanisms of these products to enable the selection of proper biostimulants, application methods, and dosage in viticulture. A detailed understanding of processes dictating beneficial effects in vineyards following application may allow for biostimulants with increased efficacy, uptake, and sustainability.