Valorization of Capsicum annuum seed extract as an antifungal against Botrytis cinerea

Abstract

Abstract Botrytis cinerea Pers., the causal agent of gray mold, is an airborne pathogen that causes significant damage to tomato crops worldwide at all development stages and post-harvest. In this study, the aqueous extract of Capsicum annuum seeds was screened for its phytochemical constituents and assessed at various concentrations (10, 20, 30, and 60%) for antifungal activity in vitro. Selected biochemical, pathological, agronomical, physicochemical, and morphometrical traits were investigated to determine the effectiveness of applying the aqueous seed extract and salicylic acid either separately or in combination to tomato seeds and fruits in vivo. Phytochemical screening of the aqueous seed extract showed the presence of 2, 2-diphenyl-1-picrylhydrazyl, phenolic and flavonoid contents, quinic acid, protocatechuic acid, syringic acid, p-coumaric acid, trans-ferulic acid, rutin, quercetin-3-o-rhamonosic, kaempferol, naringenin, and apigenin at various concentrations. The findings suggested that the aqueous extract at a concentration of 60% was most efficient in vitro where mycelial growth was < 3.8 mm, mycelial growth inhibition was > 52%, and mycelial growth rate of < 1.05 mm/h. In vivo, the combined treatments of tomato seeds produced the greatest reduction in gray mold damage (disease severity index 8.67%) and the most favorable growth parameters of seedlings were chlorophyll a > 1.50 mg/g.f.Wt.; chlorophyll b > 1.76 mg/g.f. Wt.; total chlorophyll content > 3.26 mg/g.f.Wt.; seedling fresh weight > 0.43 g; seedling length > 12.43 cm, respectively. Combined preventive treatment applied to tomato fruits inoculated with B. cinerea resulted in the lowest disease severity (percentage of fruit area covered by gray mold < 33.33%; disease severity index < 46.67%) and the most favorable physicochemical attributes (water content < 98.28%; juice yield > 53.35%; pH < 3.59; titratable acidity > 1.37 g/10 ml juice; Brix degree > 4.73; nitrate content < 383.33 mg/kg; electrical conductivity < 2.47 mS/cm) and morphometrical attributes (fruit firmness > 3.03). The combined treatments resulted in the strongest activity of peroxidase (> 4.162 units/mg/min), ascorbate peroxidase (> 31.66 µmol/mg/min), and malondialdehyde (> 3.90 µmol/g) on the tomato fruits. The aqueous extract of C. annuum seeds combined with salicylic acid had positive effects in terms of inhibiting B. cinerea and is thus a promising and environmentally friendly alternative substitute for chemical fungicides towards sustainable agriculture under climate change.