Impact of Shading Net Color on Phytochemical Contents in Two Chili Pepper Hybrids Cultivated Under Greenhouse Conditions

Abstract

The objective of this study was to understand the combined effect of shading treatment and harvest time on pungency, ascorbic acid content, market-quality pepper yield, and photosynthetic activity in a yellow ‘Star Flame’ and ‘Fire Flame’ F1 hybrid pepper cultivar (Capsicum annuum). Plants were cultivated in a greenhouse under white, red, and green shading nets and compared to those grown under unshaded control conditions. The ascorbic acid and pungency parameters were analyzed by high-performance liquid chromatographic methods. Ascorbic acid, a compound of high nutritive value in pepper, was highest in fruits gathered during the first summer harvest in both hybrids. The ascorbic acid content was found to be further increased in fruits from plants grown under white net shading in both ‘Star Flame’ and ‘Fire Flame’. Total capsaicinoid contents in ‘Star Flame’ were influenced by the interaction of shading treatment and harvest time ( p = 0.004), with the lowest amounts (241.2-251.5 mg·kg-1 fresh weight) resulting from white and red shading treatments at the early autumn harvest. In ‘Fire Flame’, both shading treatment ( p = 0.009) and harvest time ( p < 0.001) affected total capsaicinoid contents. We observed significantly higher total capsaicinoid contents in control fruits compared to that resulting from red and green shading treatments at the second harvest, and that resulting from red shading treatment at the third harvest. Analysis of photosynthetic activity revealed a significant and negative correlation between Fv/Fm values and total capsaicinoid contents in both hybrids ( p < 0.001). Based on the obtained results, the harvest of peppers during summer should be promoted to produce fruits with high pungency.