Phenology, yield, and phytochemicals of Capsicum spp. in response to shading

Background: Capsicum spp. grow in environments with different incident radiation, that could modify the plant growth and the concentration of phytochemicals in fruits. Hypothesis: Shading positively affects phenology and fruit yield, decreases the total contents of phenols (TPC), flavonoids (FLV), proanthocyanidins (PAN) and carotenoids (CAT) in fruits of wild Capsicum species. Studied species: Capsicum annuum var. glabriusculum: amashito (AMA) and garbanzo (GAR), and C. frutescens (Pico Paloma, PIP) Study site and dates: Huimanguillo, Tabasco, Mexico; 2020 and 2021. Methods: Seeds were treated with gibberellic acid (GA3) (500 mg L-1) for 24 h prior to seeding. The seedlings were transplanted in an open field and under two levels of shade (35 and 70 %) under a subsplit plot design with four replicates. TPC, FLV, PAN and CAT were determinate in immature and ripe fruits by UV-vis spectrophotometry. Results: Shade accelerated the phenological processes from the first bifurcation of the stem, and decreased the fruits ripening time from anthesis of the genotypes studied. Shade only increased the yield of the AMA genotype and reduced the contents of TPC, FLV, and CAT; however, these metabolites increased under open field conditions. Conclusions: The shade reduced the duration of phenological stages including the ripening period of fruits, and increased the plant height of the Capsicum spp. The increase in yield by shading effect only was observed in AMA genotype. The content of phytochemicals in Capsicum fruits is reduced by shading levels.