Evaluation of foliar application of 1,3-β-glucan in grapevine: nutritional and vegetative aspects

The biostimulant Valena™ Flow (VF), the unique source of 1,3-β-glucan (ßG) material derived from Kemin’s microalgae Euglena gracilis, known to elicit plant defense responses was tested in young vines in a greenhouse during the 2022-2023 period. The aim of the trial was focused on the evaluation of different doses of the product (32% 1,3-β-glucan, 2% zinc) sprayed by foliar application. Substances like 1,3- β-glucan are viewed as pathogen-associated molecular patterns by pattern recognition receptors present naturally in plant cells, meaning that its presence can be mistaken for pathogens by the plant, increasing a way to fight off potential pathogens, even if no real attack exists, enhancing the nutritional uptake favorable to plant growth. Three different treatments, replicated three times (6 plants/repetition), were compared in 2022: treated only with water (Water), 0.60 L ha-1 VF (224 ppm ßG), and 2 L ha-1 VF (748 ppm ßG). In 2023, two lower doses of the product – 0.15 and 0.30 L ha-1 VF (56 and 112 ppm ßG) – were added, reaching five different theses, and 90 vines. In both years of trial, vegetative and productive behavior were investigated, dividing plants into different organs (leaves, fine and coarse roots, shoots, and annual wood). Regarding mineral nutritional aspects, in both years, the contents in leaves, roots, shoots, and wood were analyzed. The effect of the biostimulant modified the color of the vegetation and the biomass produced by the plants. The epigeal organs showed similar growth to the untreated control, but significant increases of root biomass were observed with the use of the biostimulant. In 2023, the effect was evident proportionally to the dosage of the biostimulant applied, until 224 ppm ßG, decreasing when the highest dose was used. Significant increases of N, P, K, Ca, Mg, S, Fe, Mn, and B contents were recorded when the biostimulant was applied to the plants