Methyl jasmonate and type of fertilization affect growth, production and accumulation of sulforaphane in black radish taproot

ABSTRACT Arable areas frequently lack sufficient soil nutrients, necessitating use of fertilizers, whose excessive usage presents a threat to the environment, human health, and food safety. Natural plant-based growth regulators are inexpensive and favorable to the environment. Phytohormone methyl jasmonate (MeJA) is important in improving quality, productivity, and resistance against various pests, diseases, and environmental challenges. The objectives of this study were to compare effects of fertilization and application of MeJA on taproot yield, leaf nutritive value, and accumulation of sulforaphane (SF) in black radish (Raphanus sativus L. var. niger) taproots. Sulforaphane is a potent cytoprotective agent, promoting antioxidant, anti-inflammatory, antiglycative, and antimicrobial effects. The treatments (T) were: T1 = 3 t∙ha−1 of poultry litter (PL); T2 = PL+2.5 ml∙L−1 foliar application of micro-sulfur (S); T3 = PL+S+3 g∙L−1foliar application of sorbitol (SO); T4 = 480 kg∙ha−1 of NPK 20,20,20; T5 = NPK+S; T6 = NPK+S+SO. The second experiment was foliar application of MeJA at 0, 50, or 100 mg∙L−1. Application of treatments and MeJA alone, and in combination, improved growth, leaf nutrient concentrations, taproot yield components, and accumulation of SF in black radish. The T3 treatment produced the highest relative chlorophyll content (SPAD index = 31.56), most leaf area (495.33 dm2), tallest plants and longest taproot (57.95 and 17.68 cm), highest dry matter of leaf and taproot (8.10 and 12.57%), heaviest fresh weight of leaves and taproots (249.15 and 360.40 g) and highest total taproot yield (120.13 t∙ha−1). Treatment T6 produced highest nitrogen (N), phosphorus (P) and potassium (K) content in leaves, 3.57, 0.52 and 3.87 g 100 g, respectively, and highest SF content in taproots (8.5 mg/100 g). The 100 mg∙L−1 MeJA rate produced the largest leaf area (480.10 dm2), highest dry matter of leaf and taproot (7.31 and 11.65%), heaviest fresh weight of taproot (356.23 g), highest N, P, K and S content in leaves (3.45, 0.47, 3.69 and 0.375 g/100 g), most taproot yield (118.74 t∙ha−1) and highest FS content in taproot (9.62 g/100 g). The 100 mg∙L−1 foliar application of MeJA was effective in increasing and improving vegetative growth, taproot productivity, and FS accumulation in black radish.