Spatiotemporal shading regulates anthocyanin, proanthocyanidin, and sucrose accumulation in black soybean seeds

Abstract

AbstractThe accumulation of soybean seed constituents such as anthocyanin, proanthocyanidin (PA), and sucrose is affected by various environmental stresses. Considerable information is available on the effects of different environmental stresses; however, the effect of shade at various development stages on the accumulation of the various seed constituents remains elusive. We investigated the effect of shade application on anthocyanin, PA, and sucrose contents at different seed development stages of two black soybean [Glycine max (L.) Merr.] varieties. This study comprised two separate trials: maize–soybean relay intercropping (IC) and soybean monoculture. The shade treatments in the soybean monoculture trial comprised shade applications at whole growth stage, at vegetative stage (SV), and at reproductive stage (SR) and a no‐shade control. Anthocyanin, PA, and sucrose contents were analyzed from seeds obtained at development stages of full‐size seed (R6), physiological maturity (R7), full maturity, 95% mature pods on the plant (R8), and natural air dry (AD). Genotype, shade, and planting season and their interactions had a strong influence on anthocyanin, PA, and sucrose accumulation in soybean seeds at the different seed development stages. Among all the shade treatments, relay IC recorded the highest anthocyanin contents in 2017 (1.88 mg g−1) and 2018 (1.76 mg g−1) in AD seeds. In addition, the application of shade increased PA, and maximum PA (27.14 mg g−1) was obtained in the SV treatment at R6 stage. The overall best sucrose contents (6.14 mg g−1 in 2017 and 7.04 mg g−1 in 2018) were obtained in soybean seeds harvested at R8 under SV treatment.